The effect of open access and downloads ('hits') on citation impact: a bibliography of studies

Abstract: Since 1998 studies have shown that open access increases impact as measured by the number of citations. This chronological and comprehensive bibliography of those reports provides a way of investigating the meaning of that statement, to understand its effect, to recognise the significant factors involved, and identify the causal relationships between the respective factors. Reviews in 2010 suggest a ratio of between 5.5:1 and 7:1 of studies showing an open access citation advantage against those that do not. The bibliography also lists the Web tools available to measure impact. It is a focused bibliography, on the relationship between impact and access. It does not attempt to cover citation impact, or other related topics such as open access, more generally, although some key papers in these areas are listed as jump-off points for wider study. Other important effects can be found in the area of research assessment. There is an occasionally updated section on the correlation between research access, impact and assessment. This is a snapshot of the bibliography taken towards the end June 2013. The research on this topic continues, as does the updated version of the bibliography.

Last updated 25 June 2013; first posted 15 September 2004 (as a follow-on from the JISC-NSF Open Citation Project).
If you have any additions, corrections or comments, please tweet @stevehit #oaimpact or email Steve Hitchcock.

"a brilliant source of articles" (on impact of Open Access material)
Christine Stohn, Ex Libris Initiatives (3 September 2012)

A great resource!
Eloy Rodrigues, University of Minho, via Twitter (July 17, 2009)

"This ongoing chronological bibliography may be worth bookmarking and checking every few months. There's very little annotation, but it's a good brief bibliography on a narrow - but important - subject."
Walt Crawford, Cites & Insights (November 2004, p13) http://citesandinsights.info/civ4i13.pdf

Citations of this bibliography found by Google Scholar
Web pages that link to this bibliography found by Google

Introduction to the bibliography

This chronological bibliography is intended to describe progress in reporting these studies; it also lists the Web tools available to measure impact. It is a focused bibliography, on the relationship between impact and access. It does not attempt to cover citation impact, or other related topics such as open access, more generally, although some key papers in these areas are listed as jump-off points for wider study.

Simple and practical example

"Measuring the effect for physics or astronomy is easy. This link returns the number of articles published in the Astrophysical Journal in 2003 and their number of citations.

"This next link shows the number of these papers which are available OA in the arXiv, and their citations.

"The result is that 75% of the papers are in the arXiv, and they represent 90% of the citations, a 250% OA effect.

"By replacing ApJ with the mnemonic for any other physics or astronomy journal one can repeat the measurement; for Nuclear Physics A (NuPhA) one gets that 32% of the articles are in the arXiv, and they represent 78% of the citations, a 740% OA effect."
From Michael Kurtz, American Scientist Open Access Forum, 28 September 2005 http://users.ecs.soton.ac.uk/harnad/Hypermail/Amsci/4807.html
Note, the database links are 'live', i.e. they return the current database figures, not the exact figures on which Michael Kurtz would have based his calculations, but the percentages quoted are unlikely to change dramatically, in the short term at least.

Elucidation of calculation (by Stevan Harnad, figures valid on 22 July 2007)
For ApJ:
TOT: articles 2592 citations 70732
Arx: articles 1943 citations 62586 c/a 32.21 (rounded to 32)
Non: articles 649 citations 8146 c/a 12.55 (rounded to 13)
Then 32/13 = 2.5 (250%)

For NuPhA:
TOT: articles 1134 citations 4451
Arx: articles 344 citations 3225 c/a 9.375
Non: articles 790 citations 1226 c/a 1.552
Then 9.375/1.553 = 6.041 (600%)

Michael Kurtz comments: "The differences in (NuPhA: 740% to 600% effect) results are because the database has changed over the past two years since I did it. There is a systematic error in the calculations for Nuclear Physics A (Elsevier does not give us the references) so the results will be higher than the true value. Physical Review C (Nuclear Physics) has an OA advantage number of 221%, the systematic in this case is small and in the other direction."

Studies with original data

Highlights

Open access has become feasible because of the move towards online publication and dissemination. A new measure that becomes possible with online publication is the number of downloads or 'hits', opening a new line of investigation. Brody et al. have been prominent in showing there is a correlation between higher downloads and higher impact, particularly for high impact papers, holding out the promise not just for higher impact resulting from open access but for the ability to predict high impact papers much earlier, not waiting years for those citations to materialise (e.g. Brody and Harnad 2005). The effect can be verified with the Correlation Generator (below).

Added 25 June 2013 Valeria Aman (2013)
The potential of preprints to accelerate scholarly communication - A bibliometric analysis based on selected journals
arXiv.org > cs > arXiv:1306.4856, 20 Jun 2013
Master Thesis. Abstract: This paper quantifies to which extent preprints in arXiv accelerate scholarly communication. The following subject fields were investigated up to the year 2012: High Energy Physics (HEP), Mathematics, Astrophysics, Quantitative Biology, and Library and Information Science (LIS). Publication and citation data was downloaded from Scopus and matched with corresponding preprints in arXiv. Furthermore, the INSPIRE HEP database was used to retrieve citation data for papers related to HEP. The bibliometric analysis deals with the growth in numbers of articles published having a previous preprint in arXiv and the publication delay, which is defined as the chronological distance between the deposit of a preprint in arXiv and its formal journal publication. Likewise, the citation delay is analyzed, which describes the time it takes until the first citation of preprints, and articles, respectively. Total citation numbers are compared for sets of articles with a previous preprint and those without. The results show that in all fields but biology a significant citation advantage exists in terms of speed and citation rates for articles with a previous preprint version on arXiv.

Added 21 June 2013 Carsten Nieder, Astrid Dalhaug and Gro Aandahl (2013)
Correlation between article download and citation figures for highly accessed articles from five open access oncology journals
SpringerPlus, 2:261, 13 June 2013
doi:10.1186/2193-1801-2-261
Abstract (provisional): Different approaches can be chosen to quantify the impact and merits of scientific oncology publications. These include source of publication (including journal reputation and impact factor), whether or not articles are cited by others, and access/download figures. When relying on citation counts, one needs to obtain access to citation databases and has to consider that results differ from one database to another. Accumulation of citations takes time and their dynamics might differ from journal to journal and topic to topic. Therefore, we wanted to evaluate the correlation between citation and download figures, hypothesising that articles with fewer downloads also accumulate fewer citations. Typically, publishers provide download figures together with the article. We extracted and analysed the 50 most viewed articles from 5 different open access oncology journals. For each of the 5 journals and also all journals combined, correlation between number of accesses and citations was limited (r = 0.01-0.30). Considerable variations were also observed when analyses were restricted to specific article types such as reviews only (r = 0.21) or case reports only (r = 0.53). Even if year of publication was taken into account, high correlation coefficients were the exception from the rule. In conclusion, downloads are not a universal surrogate for citation figures.

Added 17 June 2013 Vincent Lariviere, Cassidy R. Sugimoto, Benoit Macaluso, Stasa Milojevic, Blaise Cronin, Mike Thelwall (2013)
arXiv e-prints and the journal of record: An analysis of roles and relationships
arXiv.org > cs > arXiv:1306.3261, 13 Jun 2013
Abstract: Since its creation in 1991, arXiv has become central to the diffusion of research in a number of fields. Combining data from the entirety of arXiv and the Web of Science (WoS), this paper investigates (a) the proportion of papers across all disciplines that are on arXiv and the proportion of arXiv papers that are in the WoS, (b) elapsed time between arXiv submission and journal publication, and (c) the aging characteristics and scientific impact of arXiv e-prints and their published version. It shows that the proportion of WoS papers found on arXiv varies across the specialties of physics and mathematics, and that only a few specialties make extensive use of the repository. Elapsed time between arXiv submission and journal publication has shortened but remains longer in mathematics than in physics. In physics, mathematics, as well as in astronomy and astrophysics, arXiv versions are cited more promptly and decay faster than WoS papers. The arXiv versions of papers - both published and unpublished - have lower citation rates than published papers, although there is almost no difference in the impact of the arXiv versions of both published and unpublished papers.

Added 17 June 2013 Pekka Olsbo (2013)
Does Openness and Open Access Policy Relate to the Success of Universities?
17th International Conference on Electronic Publishing, Karlskrona, Sweden, June 13-14, 2013
full paper http://elpub.scix.net/data/works/att/110_elpub2013.content.01124.pdf
Extended Abstract. Introduction: The cross reading and examination of the report The state of scientific research in Finland 2012 by The Finnish Academy and Ranking Web of Universities seem to show that there could be a connection between the internet visibility, ranking and the relative citation impact of universities in different countries. These relationships can be traced back to the effectiveness of the open access publishing, self-archiving and Open Access policies of the countries and the universities. This paper focuses on internet visibility of the University of Jyväskylä and eight European countries and how the openness of universities has developed during last two editions of the Ranking Web of Universities.

Added 28 May 2013 Mark J. McCabe, Christopher M. Snyder (2013)
The Rich Get Richer and the Poor Get Poorer: The Effect of Open Access on Cites to Science Journals Across the Quality Spectrum
Social Science Research Network SSRN, May 25, 2013
Abstract: An open-access journal allows free online access to its articles, obtaining revenue from fees charged to submitting authors. Using panel data on science journals, we are able to circumvent some problems plaguing previous studies of the impact of open access on citations. We find that moving from paid to open access increases cites by 8% on average in our sample, but the effect varies across the quality of content. Open access increases cites to the best content (top-ranked journals or articles in upper quintiles of citations within a volume) but reduces cites to lower-quality content. We construct a model to explain these findings in which being placed on a broad open-access platform can increase the competition among articles for readers attention. We can find structural parameters allowing the model to fit the quintile results quite closely.

Added 13 May 2013 Cassidy R. Sugimoto, Mike Thelwall, Vincent Larivière, Andrew Tsou, Philippe Mongeon, Benoit Macaluso (2013)
Scientists Popularizing Science: Characteristics and Impact of TED Talk Presenters
PLoS ONE, 8(4): e62403, April 30, 2013
doi:10.1371/journal.pone.0062403
Abstract: The TED (Technology, Entertainment, Design) conference and associated website of recorded conference presentations (TED Talks) is a highly successful disseminator of science-related videos, claiming over a billion online views. Although hundreds of scientists have presented at TED, little information is available regarding the presenters, their academic credentials, and the impact of TED Talks on the general population. This article uses bibliometric and webometric techniques to gather data on the characteristics of TED presenters and videos and analyze the relationship between these characteristics and the subsequent impact of the videos. The results show that the presenters were predominately male and non-academics. Male-authored videos were more popular and more liked when viewed on YouTube. Videos by academic presenters were more commented on than videos by others and were more liked on YouTube, although there was little difference in how frequently they were viewed. The majority of academic presenters were senior faculty, males, from United States-based institutions, were visible online, and were cited more frequently than average for their field. However, giving a TED presentation appeared to have no impact on the number of citations subsequently received by an academic, suggesting that although TED popularizes research, it may not promote the work of scientists within the academic community.
See also
Sara Grossman, Giving a TED Talk? Expect More Visibility, but Not More Citations, Chronicle of Higher Education, June 19, 2013

Added 13 May 2013 Xianwen Wang, Wenli Mao, Shenmeng Xu, Chunbo Zhang (2013)
Attention History Over Time of Scientific Literature: Metrics of Nature Publications
arXiv.org > cs > arXiv:1304.7653, 29 Apr 2013
Abstract: In this study, we report findings about patterns of the Nature metrics page views over time. Using the page views data of papers published on Nature, we calculate from two perspectives. The first one is the time before their page views reach 50%/80% of the total, and the second one is the percentage of total page views in 7 days, 30 days, and 100 days after publication. Papers are viewed most frequently within a short time period after publication. Respectively, 62.16% and 100% of the papers on Nature are viewed more than half of their total times in the first week and month. 52.48% of the papers gain more than 80% of their total views in the following month. Meanwhile, the page views number reaches more than 52% of the total in the first week and more than 72% in the first month. In addition, we find that readers' attention on Open Access publications are more enduring. Using the usage data of a newly published paper, we conduct regression analysis to predict the future expected total usage count of the paper.

Added 13 May 2013 Teja Koler-Povh, Goran Turk and Primo Juni (2013)
Does the Open Access Business Model Have a Significant Impact on the Citation of Publications? Case Study in the Field of Civil Engineering
Proceedings of the Fifth Belgrade International Open Access Conference 2012, 26 April 2013
DOI: 10.5937/BIOAC-68
Original conference slide presentation, 18 May 2012 http://boac.ceon.rs/public/site/Koler-Povh_Juznic_Turk.pdf
From the abstract: we have chosen to analyze the publications in three international journals in the field of civil engineering. All of them have an ISI impact factor in the Civil engineering subject category in the ISI/Web of science database (WOS). The articles were classified into two groups - the OA publications and the non-OA publications. We analyzed all the articles published in the same year and the number of their citations until the end of February 2012, seeking to find out if these two groups differ from each other. From the conclusion: It was found that OA significantly influenced the citation counts for the articles published in the Computers & Structures journal, which is ranked in the first quarter - according to both databases. Only the GS database showed a significant effect of OA on citations for the articles published in the Journal of Computing in Civil Engineering. Neither GS nor WOS databases indicate a significant effect of OA on the citation counts of articles in the Automation in Construction journal. These two journals are ranked in the second quarter among 88 journals in the same subject category, civil engineering. The present results indicate that more research is needed to give a final answer to the principle question of the paper: does open access have a significant impact on citations in the field of civil engineering. Some other potentially influential factors will be tested as well.

Added 13 May 2013 Vincent Larivière, George A. Lozano, Yves Gingras (2013)
Are elite journals declining?
arXiv.org > cs > arXiv:1304.6460, 24 Apr 2013
Previous work indicates that over the past 20 years, the highest quality work have been published in an increasingly diverse and larger group of journals. In this paper we examine whether this diversification has also affected the handful of elite journals that are traditionally considered to be the best. We examine citation patterns over the past 40 years of 7 long-standing traditionally elite journals and 6 journals that have been increasing in importance over the past 20 years. To be among the top 5% or 1% cited papers, papers now need about twice as many citations as they did 40 years ago. Since the late 1980s and early 1990s elite journals have been publishing a decreasing proportion of these top cited papers. This also applies to the two journals that are typically considered as the top venues and often used as bibliometric indicators of "excellence", Science and Nature. On the other hand, several new and established journals are publishing an increasing proportion of most cited papers. These changes bring new challenges and opportunities for all parties. Journals can enact policies to increase or maintain their relative position in the journal hierarchy. Researchers now have the option to publish in more diverse venues knowing that their work can still reach the same audiences. Finally, evaluators and administrators need to know that although there will always be a certain prestige associated with publishing in "elite" journals, journal hierarchies are in constant flux so inclusion of journals into this group is not permanent.
See also
Hadas Shema, Elite journals: to hell in a handbasket? Scientific American blogs, May 2, 2013

Added 13 May 2013 Paola Bongiovani, Sandra Miguel, Nancy Diana Gómez
Acceso abierto, impacto científico y la producción científica en dos universidades argentinas en el campo de la medicina (Open Access, scientific impact and the scientific production in two Argentine universities in the field of medicine)
Revista Cubana de Información en Ciencias de la Salud, Vol 24, No 2, 2013
Abstract: this paper studies the scientific production published by researchers at two argentine universities (National University of La Plata and National University of Rosario) in the discipline of medicine. Objective: to establish the volume and evolution of scientific production published in open access journals and in subscription journals that allow self-archiving in repositories. Methods: The scientific production for both institutions was determined by taking a sample from Scopus and covers the period 2006-2010. It applies a methodology based on the analysis of the access models of journals used by researchers to publish their articles established through searches performed using Romeo-Sherpa, Dulcinea, DOAJ, SciELO, RedALyC and PubMed Central. Additionally, the study explores the citation levels of articles from both institutions according to access models of journals, comparing impact indicators from average citation per article. Results: The two institutions generally show similar patterns to those found at national level, although UNR, following international trends in Medicine, has a higher percentage of articles published in open access journals. In both cases, about half of the production could be deposited in repositories, being pre-print versions and the author's post print mostly allowed by editors. Conclusions: From the perspective of the impact levels achieved, the results indicate a higher level of citation in subscription journals with self-archiving permissions, and this is encouraging for the promotion and development of institutional repositories in both universities.

Added 9 April 2013 Xin Shuai, Zhuoren Jiang, Xiaozhong Liu, Johan Bollen (2013)
A Comparative Study of Academic impact and Wikipedia Ranking
Author preprint. Joint Conference on Digital Libraries JCDL 2013, Indianapolis, IN, July 22-26, 2013, to be presented
Abstract: In addition to its broad popularity Wikipedia is also widely used for scholarly purposes. Many Wikipedia pages pertain to academic papers, scholars and topics providing a rich ecology for scholarly uses. Although many recognize the scholarly potential of Wikipedia, as a crowdsourced encyclopedia its authority and quality is questioned due to the lack of rigorous peer-review and supervision. Scholarly references and mentions on Wikipedia may thus shape the societal impact of a certain scholarly communication item, but it is not clear whether they shape actual academic impact. In this paper we compare the impact of papers, scholars, and topics according to two different measures, namely scholarly citations and Wikipedia mentions. Our results show that academic and Wikipedia impact are positively correlated. Papers, authors, and topics that are mentioned on Wikipedia have higher academic impact than those are not mentioned. Our findings validate the hypothesis that Wikipedia can help assess the impact of scholarly publications and underpin relevance indicators for scholarly retrieval or recommendation systems.

Added 9 April 2013 Heather Piwowar, Todd J Vision (2013)
Data reuse and the open data citation advantage
PeerJ PrePrints, v1, 4 Apr 2013
doi: 10.7287/peerj.preprints.1
From the Abstract: Previous studies have found that papers with publicly available datasets receive a higher number of citations than similar studies without available data. However, few previous analyses have had the statistical power to control for the many variables known to predict citation rate, which has led to uncertain estimates of the citation boost. Furthermore, little is known about patterns in data reuse over time and across datasets. METHOD AND RESULTS: Here, we look at citation rates while controlling for many known citation predictors, and investigate the variability of data reuse. In a multivariate regression on 10,555 studies that created gene expression microarray data, we found that studies that made data available in a public repository received 9% (95% confidence interval: 5% to 13%) more citations than similar studies for which the data was not made available. Date of publication, journal impact factor, open access status, number of authors, first and last author publication history, corresponding author country, institution citation history, and study topic were included as covariates. The citation boost varied with date of dataset deposition: a citation boost was most clear for papers published in 2004 and 2005, at about 30%. ... CONCLUSION: After accounting for other factors affecting citation rate, we find a robust citation benefit from open data, although a smaller one than previously reported. We conclude there is a direct effect of third-party data reuse that persists for years beyond the time when researchers have published most of the papers reusing their own data.

Added 9 April 2013 Philip M. Davis (2013)
Public accessibility of biomedical articles from PubMed Central reduces journal readership - retrospective cohort analysis
The FASEB Journal, Federation of American Societies for Experimental Biology, April 3, 2013
doi: 10.1096/fj.13-229922
Abstract: Does PubMed Centrala government-run digital archive of biomedical articlescompete with scientific society journals? A longitudinal, retrospective cohort analysis of 13,223 articles (5999 treatment, 7224 control) published in 14 society-run biomedical research journals in nutrition, experimental biology, physiology, and radiology between February 2008 and January 2011 reveals a 21.4% reduction in full-text hypertext markup language (HTML) article downloads and a 13.8% reduction in portable document format (PDF) article downloads from the journals websites when U.S. National Institutes of Health-sponsored articles (treatment) become freely available from the PubMed Central repository. In addition, the effect of PubMed Central on reducing PDF article downloads is increasing over time, growing at a rate of 1.6% per year. There was no longitudinal effect for full-text HTML downloads. While PubMed Central may be providing complementary access to readers traditionally underserved by scientific journals, the loss of article readership from the journal website may weaken the ability of the journal to build communities of interest around research papers, impede the communication of news and events to scientific society members and journal readers, and reduce the perceived value of the journal to institutional subscribers.

Added 28 March 2013 David J Solomon, Mikael Laakso, Bo-Christer Björk (2013)
A longitudinal comparison of citation rates and growth among open access journals
Author preprint, 27 March 2013. In Journal of Informetrics, accepted for publication
Abstract: The study documents the growth in the number of journals and articles along with the increase in normalized citation rates of open access (OA) journals listed in the Scopus bibliographic database between 1999 and 2010. Longitudinal statistics on growth in journals/articles and citation rates are broken down by funding model, discipline, and whether the journal was launched or had converted to OA. The data were retrieved from the web sites of SCIMago Journal and Country Rank (journal /article counts), JournalM3trics (SNIP2 values), Scopus (journal discipline) and Directory of Open Access Journals (DOAJ) (OA and funding status). OA journals/articles have grown much faster than subscription journals but still make up less that 12% of the journals in Scopus. Two-year citation averages for journals funded by article processing charges (APCs) have reached the same level as subscription journals. Citation averages of OA journals funded by other means continue to lag well behind OA journals funded by APCs and subscription journals. We hypothesize this is less an issue of quality than due to the fact that such journals are commonly published in languages other than English and tend to be located outside the four major publishing countries.

Added 4 March 2013, updated 13 May 2013 Jerome Vanclay (2013)
Factors affecting citation rates in Environmental Science
ePublications@SCU, Southern Cross University, 2013. In Journal of Informetrics, Vol 7, No 2, April 2013, 265-271 http://www.sciencedirect.com/science/article/pii/S1751157712000995
http://dx.doi.org/10.1016/j.joi.2012.11.009
Abstract: Analysis of 131 publications during 2006-07 by staff of the School of Environmental Science and Management at Southern Cross University reveals that the journal impact factor, article length and type (i.e., article or review), and journal self-citations affect the citations accrued to 2012. Authors seeking to be well cited should aim to write comprehensive and substantial review articles, and submit them to journals with a high impact factor which has previously carried articles on the topic. Nonetheless, strategic placement of articles is complementary to, and no substitute for careful crafting of good quality research. Evidence remains equivocal regarding the contribution of an authors prior publication success (h-index) and of open-access journals.

Added 4 March 2013, updated 13 May 2013 Caitlin Rivers (2013)
Scholarly impact of open access journals
18 March 2013 (originally written on 26 January 2013)
Data sources for this work also available on Figshare http://figshare.com/articles/Open_access_journal_impacts/154346
Extracts: I downloaded a list of open access journals from the Directory of Open Access Journals (DOAJ). I also downloaded a spreadsheet of 2011 impact data from Journal Metrics, an offshoot of Scopus that assesses journal impact. Journal Metrics provides two impact measures: Source Normalized Impact per Paper (SNIP) and SCImago Journal Rank (SGR). ... In terms of impact, open access still lags behind non-OA journals. The mean SNIP of non-OA journals in 2011 was 0.83 with a max of 41, while OA journals had a mean SNIP of .57 and a max of less than 5. The mean SJR of non-OA was .64 (max of 36), and the OA mean was .38 (max of 7.6).

Added 19 March 2013, updated 13 May 2013 Mark J. McCabe, Christopher M. Snyder (2013)
Does Online Availability Increase Citations? Theory and Evidence from a Panel of Economics and Business Journals
Social Science Research Network (SSRN), 14 March 2013, also at http://mccabe.people.si.umich.edu/McCabe_Snyder_Revised_3_2013.pdf. Submitted to Review of Economics and Statistics.
Revised preprint. Abstract: Does online availability boost citations? The answer has implications for issues ranging from the value of a citation to the sustainability of open-access journals. Using panel data on citations to economics and business journals, we show that the enormous effects found in previous studies were an artifact of their failure to control for article quality, disappearing once we add fixed effects as controls. The absence of an aggregate effect masks heterogeneity across platforms: JSTOR stands apart from others, boosting citations around 10%. We examine other sources of heterogeneity including whether JSTOR increases cites from authors in developing more than developed countries and increases cites to long-tail more than superstar articles. Our theoretical analysis informs the econometric specification and allows us to translate our results for citation increases into welfare terms.

Added 4 March 2013 Richard C. Doty (2013)
Tenure-Track Science Faculty and the 'Open Access Citation Effect'
Journal of Librarianship and Scholarly Communication, 1 (3), Mar 2013
info:doi/10.7710/2162-3309.1052
From the Abstract: The observation that open access (OA) articles receive more citations than subscription-based articles is known as the OA citation effect (OACE). Implicit in many OACE studies is the belief that authors are heavily invested in the number of citations their articles receive. This study seeks to determine what influence the OACE has on the decision-making process of tenure-track science faculty when they consider where to submit a manuscript for publication. METHODS Fifteen tenure-track faculty members in the Departments of Biology and Chemistry at the University of North Carolina at Chapel Hill participated in semi-structured interviews employing a variation of the critical incident tecnique. RESULTS Seven of the fifteen faculty members said they would consider making a future article freely-available based on the OACE. Due to dramatically different expectations with respect to the size of the OACE, however, only one of them is likely to seriously consider the OACE when deciding where to submit their next manuscript for publication. DISCUSSION Journal reputation and audience, and the quality of the editorial and review process are the most important factors in deciding where to submit a manuscript for publication. Once a subset of journals has satisfied these criteria, financial and access issues compete with the OACE in making a final decision.

Added 19 March 2013 Mazda Farshad, Claudia Sidler, Christian Gerber (2013)
Association of scientific and nonscientific factors to citation rates of articles of renowned orthopedic journals
European Orthopaedics and Traumatology, March 2013
info:doi/10.1007/s12570-013-0174-6
From the Abstract: This investigation studied associations of scientific and nonscientific criteria with the citation frequency of articles in two top-ranked international orthopedic journals. Methods: The 100 most (mean, 88 citations/5 years for cases) and 100 least (mean, two citations/5 years for controls) cited articles published between 2000 and 2004 in the Journal of Bone and Joint Surgery and the Bone & Joint Journal (formerly known as JBJS (Br)), two of the most distributed general orthopedic journals, were identified. The association of scientific and nonscientific factors on their citation rate was quantified. Results: Randomized controlled trials, as well as multicenter studies with large sample sizes, were significantly more frequent in the high citation rate group. The unadjusted odds of a highly cited article to be supported by industry were 2.8 (95 % confidence interval 1.5, 5.6; p<0.05) if compared with a lowly cited article.

Added 4 March 2013 Steffen Bernius, Matthias Hanauske, Berndt Dugall, and Wolfgang Konig (2013)
Exploring the Effects of a Transition to Open Access: Insights from a Simulation Study
Goethe University Frankfurt, Faculty of Economics and Business Administration, 2012. In Journal of the American Society for Information Science and Technology, Vol. 64, No. 4, 701-726, April 2013, online: 21 Feb 2013
DOI: 10.1002/asi.22772
Abstract: The Open Access (OA) movement, which postulates gratis and unrestricted online access to publicly funded research findings, has significantly gained momentum in recent years. The two ways of achieving OA are self-archiving of scientific work by the authors (Green OA) and publishing in OA journals (Gold OA). But there is still no consensus which model should be supported in particular. The aim of this simulation study is to discover mechanisms and predict developments that may lead to specific outcomes of possible market transformation scenarios. It contributes to theories related to OA by substantiating the argument of a citation advantage of OA articles and by visualizing the mechanisms of a journal system collapsing in the long-term due to the continuation of the serials crisis. The practical contribution of this research stems from the integration of all market players: Decisions regarding potential financial support of OA models can be aligned with our findings as well as the decision of a publisher to migrate his journals to Gold OA. Our results indicate that for scholarly communication in general, a transition to Green OA combined with a certain level of subscription-based publishing and a migration of few top journals is the most beneficial development.

Added 4 March 2013 Christopher Hassall (2013)
Going green: self-archiving as a means for dissemination of research output in ecology and evolution
Ideas in Ecology and Evolution, 5 (2), Feb 2013
info:doi/10.4033/iee.v5i2.4555
Abstract: There is a perception that is prevalent within the academic community that access to information is being restricted by the large publishing houses that dominate academic publishing. However, self-archiving policies that are promoted by publishers provide a method by which this restriction can be relaxed. In this paper I outline the motivation behind self-archiving publications in terms of increased impact (citations and downloads of articles), increased access for the developing world, and decreased library costs. I then describe the current state of self-archiving policies in 165 ecology and evolution journals. I demonstrate that the majority (52%) of papers published in 2011 could have been self-archived in a format close to their final form. Journals with higher impacts tend to have more restrictive policies on self-archiving, and publishers vary in the extent to which they impose these restrictions. Finally, I provide a guide to academics on how to take advantage of opportunities for self-archiving using either institutional repositories or freely-available online tools.

Added 13 May 2013 Sayed-Amir Marashi, Seyed Mohammad Amin Hosseini-Nami, Khadijeh Alishah, Mahdieh Hadi, Ali Karimi, Saeedeh Hosseinian, Rouhallah RamezaniFard, Reihaneh Sadat Mirhassani, Zhaleh Hosseini, Zahra Shojaie (2013)
Impact of Wikipedia on Citation Trends
EXCLI Journal (Experimental and Clinical Sciences International online journal for advances in science), Vol. 12, 15-19, January 15, 2013, Supplementary Information (dataset, methodology)
Guest editorial, Abstract: It has been suggested that the "visibility" of an article influences its citation count. More specifically, it is believed that the social media can influence article citations. Here we tested the hypothesis that inclusion of scholarly references in Wikipedia affects the citation trends. To perform this analysis, we introduced a citation "propensity" measure, which is inspired by the concept of amino acid propensity for protein secondary structures. We show that although citation counts generally increase during time, the citation "propensity" does not increase after inclusion of a reference in Wikipedia.

Added 17 June 2013 Roudabeh Torabian, Alireza Heidari, Maryam Shahrifar, Esmail Khodadi, Safar Ali Esmaeile Vardanjani (2012)
The Relation between Self-Citation and Impact Factor in Medical Science Open Access Journals in ISI & DOAJ Databases
Life Science Journal, 9(4), 2206-2209, December 25, 2012
From the Abstract: This research aims at investigating the relation between self-citation and impact factor in the open access journals indexed in ISI and DOAJ in medical science in 2007-08. In this research, indexes such as the relation between self-citation of journal and impact factor and the effect of self-citation rate of the journal in open access performance are investigated. Research method is an analytical method conducted by using citation analysis technique. SPSS statistical software was used to examine and analyze the data and its inferential analysis methods such as Pierson Factor were used as well. Statistical society includes 168 journals. The results showed a self-citation rate of 28% for the journal. The findings indicate that there is a significant relation between self-citation and impact factor. After omitting self-citation, the level of self-citation in the performance of journals showed that 60% of the titles in the medical science experienced ranking increase, 27% experienced ranking decrease and 13% remained unchanged.

Added 4 December 2012 Christian Gumpenberger, Maria-Antonia Ovalle-Perandones, and Juan Gorraiz (2012)
On the impact of Gold Open Access journals
u:scholar, Universität Wien, November 2012. In Scientometrics
info:doi/10.1007/s11192-012-0902-7
Abstract: Gold Open Access (=Open Access publishing) is for many the preferred route to achieve unrestricted and immediate access to research output. However, true Gold Open Access journals are still outnumbered by traditional journals. Moreover availability of Gold OA journals differs from discipline to discipline and often leaves scientists concerned about the impact of these existent titles. This study identified the current set of Gold Open Access journals featuring a Journal Impact Factor (JIF) by means of Ulrichsweb, Directory of Open Access Journals and Journal Citation Reports (JCR). The results were analyzed regarding disciplines, countries, quartiles of the JIF distribution in JCR and publishers. Furthermore the temporal impact evolution was studied for a Top 50 titles list (according to JIF) by means of Journal Impact Factor, SJR and SNIP in the time interval 20002010. The identified top Gold Open Access journals proved to be well-established and their impact is generally increasing for all the analyzed indicators. The majority of JCR-indexed OA journals can be assigned to Life Sciences and Medicine. The success-rate for JCR inclusion differs from country to country and is often inversely proportional to the number of national OA journal titles. Compiling a list of JCR-indexed OA journals is a cumbersome task that can only be achieved with non-Thomson Reuters data sources. A corresponding automated feature to produce current lists on the fly would be desirable in JCR in order to conveniently track the impact evolution of Gold OA journals.

Added 4 December 2012 Ling-Ling Wu, Mu-Hsuan Huang, and Ching-Yi Chen (2012)
Citation patterns of the pre-web and web-prevalent environments: The moderating effects of domain knowledge
Journal of the American Society for Information Science and Technology, 63 (11), 2182-94, November 2012
info:doi/10.1002/asi.22710
Abstract: The Internet has substantially increased the online accessibility of scholarly publications and allowed researchers to access relevant information efficiently across different journals and databases. Because of online accessibility, academic researchers tend to read more, and reading has become more superficial, such that information overload has become an important issue. Given this circumstance, how the Internet affects knowledge transfer, or, more specifically, the citation behavior of researchers, has become a recent focus of interest. This study assesses the effects of the Internet on citation patterns in terms of 4 characteristics of cited documents: topic relevance, author status, journal prestige, and age of references. This work hypothesizes that academic scholars cite more topically relevant articles, more articles written by lower status authors, articles published in less prestigious journals, and older articles with online accessibility. The current study also hypothesizes that researcher knowledge level moderates such Internet effects. We chose the IT and Group subject area and collected 241 documents published in the pre-web period (1991-1995) and 867 documents published in the web-prevalent period (2006-2010) in the Web of Science database. The references of these documents were analyzed to test the proposed hypotheses, which are significantly supported by the empirical results.

Added 4 December 2012 V. Calcagno, E. Demoinet, K. Gollner, L. Guidi, D. Ruths, C. de Mazancourt (2012)
Flows of Research Manuscripts Among Scientific Journals Reveal Hidden Submission Patterns
Science, 11 October 2012
info:doi/10.1126/science.1227833
Abstract: The study of science-making is a growing discipline that builds largely on online publication and citation databases, while prepublication processes remain hidden. Here, we report results from a large-scale survey of the submission process, covering 923 scientific journals from the biological sciences in years 2006-2008. Manuscript flows among journals revealed a modular submission network, with high-impact journals preferentially attracting submissions. However, about 75% of published articles were submitted first to the journal that would publish them, and high-impact journals published proportionally more articles that had been resubmitted from another journal. Submission history affected postpublication impact: Resubmissions from other journals received significantly more citations than first-intent submissions, and resubmissions between different journal communities received significantly fewer citations.
See also
Philip Ball, Rejection improves eventual impact of manuscripts, Nature News, 11 Oct 2012: Just had your paper rejected? Dont worry - that might boost its ultimate citation tally. An excavation of scientific papers' usually hidden prepublication trajectories from journal to journal has found that papers published after having first been rejected elsewhere receive significantly more citations on average than ones accepted on first submission.
Ruth Williams, The Benefits of Rejection, The Scientist, 11 Oct 2012: A survey of the prepublication histories of papers reveals that manuscripts that are rejected then resubmitted are cited more often.
From Vincent Calcagno research:
More about submission flows, October 19, 2012: Mail contact to obtain the raw data file
The benefits of rejection, continued, October 23, 2012: On Figure 4A, "One result that attracts considerable attention in our article on Submission Flows"

Added 4 December 2012, updated 17 June 2013 Mikael Laakso and Bo-Christer Björk (2012)
Delayed Open Access - an overlooked high-impact category of openly available scientific literature
HARIS (Hanken Research Information System), 10 October 2012. Journal of the American Society for Information Science and Technology, published online 23 May 2013 http://onlinelibrary.wiley.com/doi/10.1002/asi.22856/abstract
DOI: 10.1002/asi.22856
Abstract: Delayed open access (OA) refers to scholarly articles in subscription journals made available openly on the web directly through the publisher at the expiry of a set embargo period. Though a substantial number of journals have practiced delayed OA since they started publishing e-versions, empirical studies concerning open access have often overlooked this body of literature. This study provides comprehensive quantitative measurements by identifying delayed OA journals, collecting data concerning their publication volumes, embargo lengths, and citation rates. Altogether 492 journals were identified, publishing a combined total of 111 312 articles in 2011. 77,8 % of these articles were made open access within 12 months from publication, with 85,4 % becoming available within 24 months. A journal impact factor analysis revealed that delayed OA journals have on average twice as high average citation rates compared to closed subscription journals, and three times as high as immediate OA journals. Overall the results demonstrate that delayed OA journals constitute an important segment of the openly available scholarly journal literature, both by their sheer article volume as well as by including a substantial proportion of high impact journals.

Added 4 December 2012 Philip Davis (2012)
The Effect of Public Deposit of Scientific Articles on Readership
The Physiologist, 55 (5), 161-5, October 2012
Note, this link will download the whole journal issue, not just the cited paper. Abstract: A longitudinal cohort analysis of 3,499 articles published in 12 physiology journals reveals a 14% reduction in full text article downloads when they are made publicly available from the PubMed Central archive. The loss of article readership from the journal website may weaken the ability of the publisher to build communities of interest around the research article, impede the communication of news and events with society members and reduce the perceived value of the journal to institutional subscribers.
See also
Philip Davis, Is PubMed Central Complementing or Competing with Journal Publishers? Scholarly Kitchen, September 20, 2012

Added 4 December 2012 G Mahesh (2012)
Open access and impact factors
Current Science, 103 (6), 610, 25 September 2012
Correspondence. Extract: The case-in-point is CSIR-NISCAIR journals. The institute publishes 17 primary journals and on the First International Open Access Day on 14 October 2008, NISCAIR made two of its journals open access and by mid-2009 all its journals were available in this mode. Going by the recently released Journal Citation Reports, for the first time two CSIR-NISCAIR journals have crossed IF 1, and as shown in Figure 1, almost all journals have increased their impact factors in 2011 over the previous years. It appears that the increased 2011 IFs are a result of the journals having gone open access from 2008 to 2009 onwards.

Added 4 December 2012 Filippo Radicchi (2012)
In science "there is no bad publicity": Papers criticized in technical comments have high scientific impact
arXiv.org > physics > arXiv:1209.4997, 22 September 2012
From the abstract: Technical comments are special types of scientific publications whose aim is to correct or criticize previously published papers. Often, comments are negatively perceived by the authors of the criticized articles because believed to make the commented papers less worthy or trusty to the eyes of the scientific community. Thus, there is a tendency to think that criticized papers are predestined to have low scientific impact. We show here that such belief is not supported by empirical evidence. We consider thirteen major publication outlets in science and perform a large-scale analysis of the citation patterns of criticized publications. We find that commented papers have not only average citation rates much higher than those of non commented articles, but also unexpectedly over-populate the set of the most cited publications within a journal. Since comments are published soon after criticized papers, comments can be viewed as early indicators of the future impact of criticized papers.

Added 14 September 2012 Sara Pérez Álvarez, Felipe P. Álvarez Arrieta, and Isidro F. Aguillo (2012)
EU FP7 research in Open Access Repositories
Digital.CSIC, the Institutional Repository of the Spanish National Research Council (CSIC), 21 Aug 2012. In 17th International Conference on Science and Technology Indicators (STI), 5-8 September 2012, Montreal, http://sticonference.org/Proceedings/vol1/Alvarez_EU_58.pdf
Abstract: Open access repositories are a reliable source of academic items that can be used for testing the capabilities of the webometric analysis. This paper deals with actions needed for extracting web indicators from bibliographic records in open access repositories, provides guidelines to support a further webometric study and presents the results of a preliminary web impact evaluation carried out over a sample of 1386 EU FP7 output papers available from the OpenAIRE database. The European Commission project OpenAIRE aims, among other objectives, to provide impact measures to assess the research performance from repositories contents and, especially, of Special Clause 39 project participants within EU FP7. Using URL citations, title mentions and copies of titles as main web impact indicators, this study suggests that a priori the implementation of the mandatory clause SC39 to encourage open access to European research may be resulted indeed in a greater and more immediate web visibility of these papers.

Added 4 December 2012 Melissa Terras (2012)
The Impact of Social Media on the Dissemination of Research: Results of an Experiment
Journal of Digital Humanities, 1 (3), September 2012
Three collected blog posts, revised with a new introduction for this journal presentation: The first, What Happens When You Tweet an Open-Access Paper discusses the correlation between talking about an individual paper online, and seeing its downloads increase. The second, Is Blogging and Tweeting About Research Papers Worth It? The Verdict discusses the overall effect of this process on all my papers, highlighting what I think the benefits of open access are. In the final post, When Was the Last Time You Asked How Your Published Research Was Doing? I talk about the link between publishers and open access, and how little we know about how often our research is accessed once it is published.

Added 16 August 2012, updated 17 June 2013 Xianwen Wang, Zhi Wang, and Shenmeng Xu (2012)
Tracing scientists' research trends realtimely
arXiv.org > cs > arXiv:1208.1349, 07 Aug 2012 In Scientometrics, 95 (2):717-729, 5 May 2013 doi: 10.1007/s11192-012-0884
From the Abstract: In this research, we propose a method to trace scientists' research trends realtimely. By monitoring the downloads of scientific articles in the journal of Scientometrics for 744 hours, namely one month, we investigate the download statistics. Then we aggregate the keywords in these downloaded research papers, and analyze the trends of article downloading and keyword downloading.

Added 16 August 2012 Maged Boulos and Patricia Anderson (2012)
Preliminary survey of leading general medicine journals use of Facebook and Twitter
Journal of the Canadian Health Libraries Association, 33 (02), 38-47, 01 Aug 2012
info:doi/10.5596/c2012-010
From the Abstract: Methods: We selected the top 25 general medicine journals on the Thomson Reuters Journal Citation Report (JCR) list. We surveyed their Facebook and Twitter presences and scanned their Web sites for any Facebook and (or) Twitter features as of November 2011. Results/Discussion: 20 of 25 journals had some sort of Facebook presence, with 11 also having a Twitter presence. Total Likes across all of the Facebook pages for journals with a Facebook presence were 321,997, of which 259, 902 came from the New England Journal of Medicine (NEJM) alone. The total numbers of Twitter Followers were smaller by comparison when compiled across all surveyed journals. Likes and Followers are not the equivalents of total accesses but provide some proxy measure for impact and popularity. Those journals in our sample making best use of the open sharing nature of social media are closed-access; with the leading open access journals on the list lagging behind by comparison.
See also this similar finding: Sandra L De Groote, Promoting health sciences journal content with Web 2.0: A snapshot in time, First Monday, Vol 17, No 8, 6 August 2012: "Traditional journals were more likely to use Web 2.0 technology than open access journals."

Added 16 August 2012 Bo-Christer Björk and David Solomon (2012)
Open access versus subscription journals: a comparison of scientific impact
BMC Medicine, 10 (1), 17 Jul 2012
info:doi/10.1186/1741-7015-10-73
From the Abstract: In the past few years there has been an ongoing debate as to whether the proliferation of open access (OA) publishing would damage the peer review system and put the quality of scientific journal publishing at risk. Our aim was to inform this debate by comparing the scientific impact of OA journals with subscription journals, controlling for journal age, the country of the publisher, discipline and (for OA publishers) their business model. A total of 610 OA journals were compared with 7,609 subscription journals using Web of Science citation data while an overlapping set of 1,327 OA journals were compared with 11,124 subscription journals using Scopus data. Overall, average citation rates, both unweighted and weighted for the number of articles per journal, were about 30% higher for subscription journals. However, after controlling for discipline (medicine and health versus other), age of the journal (three time periods) and the location of the publisher (four largest publishing countries versus other countries) the differences largely disappeared in most subcategories except for journals that had been launched prior to 1996. OA journals that fund publishing with article processing charges (APCs) are on average cited more than other OA journals. In medicine and health, OA journals founded in the last 10 years are receiving about as many citations as subscription journals launched during the same period.
See also
Open access means business: Pay-to-publish approaching same impact factor as subscription journals, Science Codex, 17 Jul 2012
David Solomon and Bo-Christer Björk, Opinion: OA Coming of Age, The Scientist, 06 Aug 2012

Added 16 August 2012 Bertil Dorch (2012)
On the Citation Advantage of linking to data
hprints.org, Nordic Arts and Humanities and Social Sciences e-print repository, 05 Jul 2012
Abstract: This paper present some indications of the existence of a Citation Advantage related to linked data, using astrophysics as a case. Using simple measures, I find that the Citation Advantage presently (at the least since 2009) amounts to papers with links to data receiving on the average 50% more citations per paper per year, than the papers without links to data. A similar study by other authors should a cummulative effect after several years amounting to 20%. Hence, a Data Sharing Citation Advantage seems inevitable.

Added 4 December 2012 Adam Eyre-Walker (2012)
Can we assess the quality and impact of science? (video)
YouTube, 02 July 2012
In International workshop on Evolution in the Time of Genomics - part 08, May 2012, Venice. Quoted extracts: "(F1000) assessors are highly influenced by the impact factor of the journal and less by the actual intrinsic quality of the paper" "Without the information of what journal that paper is published in you have very little power to tell the ultimate impact of that paper" "People tend to over-rate the quality of science in high-impact factor journals and that is a very important influence" "The difference between the really high impact journals and the medium quality journals is nothing like as dramatic as we might think" There is a brief mention of open access impact only in questions following the presentation - assumes open access journals.

Added 27 June 2012 Sharon Mathelus, Ginny Pittman, and Jill Yablonski-Crepeau (2012)
Promotion of research articles to the lay press: a summary of a three-year project
Learned Publishing, Vol 25, No 3, July 2012, 207-212
Abstract: The promotion of scholarly journal articles to journalists and bloggers via the dissemination of press releases generates a positive impact on the number of citations that publicized journal articles receive. Research by John Wiley & Sons, Inc. shows that article-level publicity efforts and media coverage boosts downloads by an average of 1.8 times and were found to increase citations by as much as 2.0-2.2 times in the articles analyzed in this study. We evaluated scholarly journal articles published in nearly 100 Wiley journals, which were also covered in 296 press releases. The results in this case study suggest a need for greater investment in media support for scholarly journals publishing research that sparks interest to a broad news audience, as it could increase citations.

Added 27 June 2012 M. Riera and E. Aibar (2012)
Does open access publishing increase the impact of scientific articles? An empirical study in the field of intensive care medicine
Medicina intensiva / Sociedad Espanola de Medicina Intensiva y Unidades Coronarias, 07 June 2012. Via NCBI PubMed.gov
info:pmid/22683044 | info:doi/10.1016/j.medin.2012.04.002
METHODS: We evaluated a total of 161 articles (76% being non-open access articles) published in Intensive Care Medicine in the year 2008. Citation data were compared between the two groups up until April 30, 2011. Potentially confounding variables for citation counts were adjusted for in a linear multiple regression model. RESULTS: The median number (interquartile range) of citations of non-open access articles was 8 (4-12) versus 9 (6-18) in the case of open access articles (p=0.084). In the highest citation range (>8), the citation count was 13 (10-16) and 18 (13-21) (p=0.008), respectively. The mean follow-up was 37.5±3 months in both groups. In the 30-35 months after publication, the average number (mean±standard deviation) of citations per article per month of non-open access articles was 0.28±0.6 versus 0.38±0.7 in the case of open access articles (p=0.043). Independent factors for citation advantage were the Hirsch index of the first signing author (=0.207; p=0.015) and open access status (=3.618; p=0.006). CONCLUSIONS: Open access publishing and the Hirsch index of the first signing author increase the impact of scientific articles. The open access advantage is greater for the more highly cited articles, and appears in the 30-35 months after publication.

Added 27 June 2012 Judit Bar-Ilan, Stefanie Haustein, Isabella Peters, Jason Priem, Hadas Shema, Jens Terliesner (2012)
Beyond citations: Scholars' visibility on the social Web
arXiv.org > cs > arXiv:1205.5611, 25 May 2012. In 17th International Conference on Science and Technology Indicators, Montreal, 5-8 Sept. 2012, http://sticonference.org/Proceedings/vol1/Bar-Ilan_Beyond_98.pdf
Abstract: Traditionally, scholarly impact and visibility have been measured by counting publications and citations in the scholarly literature. However, increasingly scholars are also visible on the Web, establishing presences in a growing variety of social ecosystems. But how wide and established is this presence, and how do measures of social Web impact relate to their more traditional counterparts? To answer this, we sampled 57 presenters from the 2010 Leiden STI Conference, gathering publication and citations counts as well as data from the presenters' Web "footprints." We found Web presence widespread and diverse: 84% of scholars had homepages, 70% were on LinkedIn, 23% had public Google Scholar profiles, and 16% were on Twitter. For sampled scholars' publications, social reference manager bookmarks were compared to Scopus and Web of Science citations; we found that Mendeley covers more than 80% of sampled articles, and that Mendeley bookmarks are significantly correlated (r=.45) to Scopus citation counts.

Added 27 June 2012 George Lozano, Vincent Lariviere, and Yves Gingras (2012)
The weakening relationship between the Impact Factor and papers' citations in the digital age
arXiv.org > cs > arXiv:1205.4328, 19 May 2012. In Journal of the American Society for Information Science and Technology, Vol 63, No 11, 21402145, November 2012 http://onlinelibrary.wiley.com/doi/10.1002/asi.22731/abstract
From the Abstract: We compare the strength of the relationship between journals' Impact Factors and the actual citations received by their respective papers from 1902 to 2009. Throughout most of the 20th century, papers' citation rates were increasingly linked to their respective journals' Impact Factors. However, since 1990, the advent of the digital age, the strength of the relation between Impact Factors and paper citations has been decreasing. This decrease began sooner in physics, a field that was quicker to make the transition into the electronic domain. Furthermore, since 1990, the proportion of highly cited papers coming from highly cited journals has been decreasing, and accordingly, the proportion of highly cited papers not coming from highly cited journals has also been increasing. Should this pattern continue, it might bring an end to the use of the Impact Factor as a way to evaluate the quality of journals, papers and researchers.
See also
George Lozano, The demise of the Impact Factor: The strength of the relationship between citation rates and IF is down to levels last seen 40 years ago, Impact of Social Sciences, 08 June 2012: Lozano discusses the recent paper that he co-authored.
Robinson Meyer, Thanks to the Web, Even Scientists Are Reading for the Articles, the Atlantic, July 9, 2012
Study reveals declining influence of high impact factor journals, Université de Montréal News, 07 Nov 2012

Added 27 June 2012 Henk Moed (2012)
Does open access publishing increase citation or download rates?
Research Trends, No. 28, May 2012
The effect of "Open Access" (OA) on the visibility or impact of scientific publications is one of the most important issues in the fields of bibliometrics and information science. During the past 10 years numerous empirical studies have been published that examine this issue using various methodologies and viewpoints. Comprehensive reviews and bibliographies are given amongst others by OPCIT, Davis and Walters and Craig et al. The aim of this article is not to replicate nor update these thorough reviews. Rather, it aims to presents the two main methodologies that were applied in these OA-related studies and discusses their potentialities and limitations. The first method is based on citation analyses; the second on usage analyses.

Added 27 June 2012 Brian Kelly and Jenny Delasalle (2012)
Can LinkedIn and Academic.edu Enhance Access to Open Repositories?
Opus: Online Publications Store, University of Bath, May 2012. In OR2012: 7th International Conference on Open Repositories, 9-13 July 2012, Edinburgh
From the Abstract: we are witnessing the increasing take-up of a range of third-party services such as LinkedIn and Academia which are being used by researchers to publish information related to their professional activities, including details of their research publications. The paper provides evidence which suggests that personal use of such services can increase the number of downloads by increasing SEO (Search Engine Optimisation) rankings through inbound links from highly ranked web sites. A survey of use of such services across Russell Group universities shows the popularity of a number of social media services. In the light of existing usage of these services this paper proposes that institutional encouragement of their use by researchers may generate increased accesses to institutional research publications at little cost to the institution. This paper concludes by describing further work which is planned in order to investigate the SEO characteristics of institutional repositories.

Added 27 June 2012 Carlos Paiva, Joao da Silveira, and Bianca Ribeiro (2012)
Articles with short titles describing the results are cited more often
Clinics, 67 (5), 509-13, May 2012. Via PubMed Central
info:doi/10.6061/clinics/2012(05)17
From the Abstract: OBJECTIVE: The aim of this study was to evaluate some features of article titles from open access journals and to assess the possible impact of these titles on predicting the number of article views and citations. RESULTS: Short-titled articles had higher viewing and citation rates than those with longer titles. Titles containing a question mark, containing a reference to a specific geographical region, and that used a colon or a hyphen were associated with a lower number of citations. Articles with results-describing titles were cited more often than those with methods-describing titles. After multivariate analysis, only a low number of characters and title typology remained as predictors of the number of citations.

Added 27 June 2012 Tom Rees, Katherine Ayling-Rouse, and Sheelah Smith (2012)
Accesses versus citations: Why you need to measure both to assess publication impact
8th Annual Meeting of ISMPP (International Society for Medical Publication Professionals), Baltimore, MD, April 23-25, 2012
Poster paper. Abstract OBJECTIVE: Article accesses and citations provide 2 metrics to assess article impact. However, the relationship between the 2 is not constant or well understood. We investigated the relationship between article accesses and citations in 3 general medicine journals with different journal rankings. RESEARCH DESIGN AND METHODS: We collected the numbers of article accesses and citations from a representative selection of original research articles published in 2009 and 2010 in 3 peer-reviewed, international, online- only, open-access journals: PLoS Medicine, BMC Medicine, and the International Journal of General Medicine (IJGM) (SCImago journal ranking 1.04, 0.49, and 0.06, respectively). RESULTS: The sample included 104 articles (2 outliers were excluded). CONCLUSION: The relationship between article accesses and citations varies, with the highest ratio of citations:access for journals with the highest journal ranking. For open-access journals with a low impact factor, overall article reach may be higher than expected on the basis of citations.

Added 27 June 2012 Patrick Vandewalle (2012)
Code Sharing is Associated with Research Impact in Image Processing
Reproducible Research Repository, EPFL, Lausanne, 23 Apr 2012. IEEE Computing in Science and Engineering, Vol 14, No 4, 42-47, July-Aug 2012
http://dx.doi.org/10.1109/MCSE.2012.63
Abstract: In computational sciences such as image processing, the publication itself is often not enough to allow other researchers to verify the results by repeating the described experiments. In many cases, supplementary material such as source code and measurement data are required, or can at least be very helpful. Still, only approximately 10% of recently published papers in image processing have code available online. One of the arguments for not making code available is the extra time required to prepare the material. In this paper, we claim that this additional time may be well spent, as the availability of code for a publication is associated with an increase in the expected number of citations. We show this with exploratory analyses of the relationship between code availability and the number of citations for image processing papers.
Note on open access citation impact on results (p4): As can be seen in the open access citation studies (such as the one by Lawrence), papers for which an online version is freely available have an increased number of citations. I did not take this into account in my analyses by adding the open access availability as another variable. Articles that have code available generally also have an online version of the article. The citation effect seen above is therefore the combined effect of the open access availability of the paper and the availability of code.

Added 23 April 2012 Henk Moed (2012)
The Effect of Open Access upon Citation Impact
Editors' Update, Elsevier.com, 22 Mar 2012
Does Open Access publishing increase citation rates? From a methodological point of view, the debate focuses on biases, control groups, sampling, and the degree to which conclusions from case studies can be generalized. This note does not give a complete overview of studies that were published during the past decade but highlights key events. An extended version of this paper will be published

Added 23 April 2012 Jason Priem, Heather Piwowar, and Bradley Hemminger (2012)
Altmetrics in the wild: Using social media to explore scholarly impact
arXiv.org > cs > arXiv:1203.4745, 20 Mar 2012
From the Abstract: In growing numbers, scholars are integrating social media tools like blogs, Twitter, and Mendeley into their professional communications. The online, public nature of these tools exposes and reifies scholarly processes once hidden and ephemeral. Metrics based on this activities could inform broader, faster measures of impact, complementing traditional citation metrics. This study explores the properties of these social media-based metrics or "altmetrics", sampling 24,331 articles published by the Public Library of Science.
See also
Heather Piwowar, Altmetrics shows that citations can't stand up to the full 31 flavours of research impact, Impact of Social Sciences, 04 Apr 2012

Added 23 April 2012 Xin Shuai, Alberto Pepe, and Johan Bollen (2012)
How the Scientific Community Reacts to Newly Submitted Preprints: Article Downloads, Twitter Mentions, and Citations
arXiv.org > cs > arXiv:1202.2461, 11 Feb 2012. PLoS ONE, 7(11): e47523, November 1, 2012 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0047523
doi:10.1371/journal.pone.0047523
Abstract: We analyze the online response of the scientific community to the preprint publication of scholarly articles. We employ a cohort of 4,606 scientific articles submitted to the preprint database arXiv.org between October 2010 and April 2011. We study three forms of reactions to these preprints: how they are downloaded on the arXiv.org site, how they are mentioned on the social media site Twitter, and how they are cited in the scholarly record. We perform two analyses. First, we analyze the delay and time span of article downloads and Twitter mentions following submission, to understand the temporal configuration of these reactions and whether significant differences exist between them. Second, we run correlation tests to investigate the relationship between Twitter mentions and both article downloads and article citations. We find that Twitter mentions follow rapidly after article submission and that they are correlated with later article downloads and later article citations, indicating that social media may be an important factor in determining the scientific impact of an article.

Added 12 February 2012 Heekyung Kim (2012)
The Effect of Free Access on the Diffusion of Scholarly Ideas
MIS Speaker's Series, University of Arizona, 24 January 2012
From the Abstract: By using a dataset from the Social Science Research Network (SSRN), an open repository of research articles, and employing a natural experiment that allows the estimation of the value of free access separate from confounding factors such as early viewership and quality differential, this study identifies the causal effect of free access on the citation counts. The natural experiment in this study is that a select group of published articles is posted on SSRN at a time chosen by their authors' affiliated organizations or SSRN, not by their authors. Using a difference-in-difference method and comparing the citation profiles of the articles before and after the posting time on SSRN against a group of control articles with similar characteristics, I estimated the effect of the SSRN posting on citation counts. The articles posted on SSRN receive more citations even prior to being posted on SSRN, suggesting that they are of higher quality. Their citation counts further increase after being posted, gaining an additional 10-20% of citations. This gain is likely to be caused by the free access that SSRN provides.

Added 12 February 2012 Jingfeng Xia and Ying Liu (2012)
Usage Patterns of Open Genomic Data
College & Research Libraries, 09 January 2012
Pre-print. Abstract: This paper uses Genome Expression Omnibus (GEO), a data repository in biomedical sciences, to examine the usage patterns of open data repositories. It attempts to identify the degree of recognition of data reuse value and understand how e-science has impacted a large-scale scholarship. By analyzing a list of 1,211 publications that cite GEO data to support their independent studies, it discovers that free data can support a wealth of high quality investigations, that the rate of open data use keeps growing over the years, and that scholars in different countries show different rates of complying with data sharing policies.

Added 12 February 2012 Jingfeng Xia and Katie Nakanishi (2012)
Self-Selection and the Citation Advantage of Open Access Articles
Online Information Review, 36 (1), 2012
(Subscription access required.) From the Abstract: This research examines the relationship between the open access availability of journal papers in anthropology and their citation conditions. We apply a statistical logistic regression model to explore this relationship, and compare two groups of papers those published in high-ranked journals and those in low-ranked journals, based on journal impact factor to examine the likelihood that open access status is correlated to scholarly impact. The results reveal that open access papers in general receive more citations. Moreover this research finds that 1) papers in high-ranked journals do not have a higher open access rate, and 2) papers in lower-ranked journals have a greater rate of citations if they are freely accessible. The findings are contrary to the existing theory that the higher citation rate of open access papers is caused by authors posting their best papers online.

Added 12 February 2012 Patricia Shields, Nandhini Rangarajan, and Lewis Stewart (2012)
Open Access Digital Repository: Sharing Student Research with the World
Journal of Public Affairs Education, 18 (1), 157-81, 2012
Note, this link will download the pdf of the full Winter 2012 journal issue - go to page 157. From the Abstract: We study the impact of content factors and search engine optimization factors on download rates of capstone papers. We examined all 290 MPA capstone papers at Texas State University which have been made available through an online digital repository for public consumption. Results show strong support for the impact of search engine factors on download rates. The implications of high download rates of MPA capstone papers on public administration research, practice, and education are discussed in this paper.

Added 12 February 2012 Gunther Eysenbach (2011)
Can Tweets Predict Citations? Metrics of Social Impact Based on Twitter and Correlation with Traditional Metrics of Scientific Impact
Journal of Medical Internet Research, 13 (4), 16 December 2011
info:doi/10.2196/jmir.2012
From the Abstract: Between July 2008 and November 2011, all tweets containing links to articles in the Journal of Medical Internet Research (JMIR) were mined. A total of 4208 tweets cited 286 distinct JMIR articles. Highly tweeted articles were 11 times more likely to be highly cited than less-tweeted articles (9/12 or 75% of highly tweeted article were highly cited, while only 3/43 or 7% of less-tweeted articles were highly cited; rate ratio 0.75/0.07 = 10.75, 95% confidence interval, 3.433.6). Top-cited articles can be predicted from top-tweeted articles with 93% specificity and 75% sensitivity. Conclusions: Tweets can predict highly cited articles within the first 3 days of article publication. Social media activity either increases citations or reflects the underlying qualities of the article that also predict citations, but the true use of these metrics is to measure the distinct concept of social impact. Social impact measures based on tweets are proposed to complement traditional citation metrics. The proposed twimpact factor may be a useful and timely metric to measure uptake of research findings and to filter research findings resonating with the public in real time.
See also
Gunther Eysenbach, Correction: Can Tweets Predict Citations? Metrics of Social Impact Based on Twitter and Correlation with Traditional Metrics of Scientific Impact, Journal of Medical Internet Research, 14 (1), 04 January 2012
info:doi/10.2196/jmir.2041
A minor error in the references section in the originally published version of the editorial by Eysenbach (J Med Internet Res 2011;13[4]:e123) on the relationship between citations and tweetations has been corrected; in addition, references being part of the dataset are no longer cited as references. The now corrected problem with the references was a formatting/presentation problem only and had no impact on the study findings.
Haydn Shaughnessy, How Could Twitter Influence Science (And Why Scientists Are on Board), Forbes, 15 Jan 2012

Comment on this paper:
Martin Fenner, CrowdoMeter or trying to understand tweets about journal papers, Gobbledygook, December 20, 2011: "This is a great study because it shows empirically what many of us felt already: Twitter is one of the fastest tools to discover newly published scholarly papers, and the number of tweets is an important measure of scholarly impact. Not surprisingly the paper has been tweeted more than 250 times in the first few days after publication, and will certainly become highly cited."
Phil Davis, Tweets, and Our Obsession with Alt Metrics, The Scholarly Kitchen, 04 Jan 2012: "(Counting) tweets as measures of 'buzz' leaves me concerned about what Twitter metrics measure and whether they can be considered a valid indicator of article impact. I have deeper reservations about this paper. I'm leery of editors who view their journal as a publication outlet for their own work ... it becomes hard to separate the paper's contribution to science from its contribution to entrepreneurship."
Gunther Eysenbach, Discussion on Davis' post, January 5, 2012: "your critique seems to me more directed at process rather than addressing the substance of the paper. In my mind, there is nothing wrong and nothing unusual about editors talking about their work as an editor in their own journal. "Eysenbach cites 66 papers and not just the 55 papers included in his dataset". This was an innocent mistake in the references, which had no impact on the results, which happened when the dois were pasted into the reference list and accidentally included references which were not part of the articles discussed. An erratum (http://www.jmir.org/2012/1/e7/) regarding the 12 extra references is already published, and the reference section has been corrected. The bottom line of the paper is that at least in the context of JMIR, tweets are useful metrics, predictive for citations, and they are potentially also useful for other journals. That's what the paper says, not more and not less. I was very careful not to generalize this to other journals." Following this comment Eysenbach makes a further 7 interventions in the discussion.
Added 23 April 2012 Claire Bower, Twimpact factors: can tweets really predict citations? BMJ Web Development Blog, 6 Jan, 2012
"A new paper is kicking up a storm in the world of altmetrics ... the very fact that it has been published and discussed so widely is surely a testament to the increasing importance of social metrics in evaluating article impact."
Added 23 April 2012 Alexis Madrigal, 'Highly Tweeted Articles Were 11 Times More Likely to Be Highly Cited', The Atlantic, Jan 13 2012: "if anything like this kind of correlation is found in other fields, a hidden value of Twitter's network will be revealed. Want to peer a year or two into the future of a scientific field?"
Added 23 April 2012 Laura Costello, Research Digest: Can Tweets Predict Citations? EdLab 02/09/2012: "The article also has fascinating implications for the marketing of academic publications."
Martin Fenner, Do more tweets mean higher citations? If so, Twitter can lead us to the personalised journal; pinpointing more research that is relevant to your interests, Impact of Social Sciences, 09 February 2012: "We need more research like the Eysenbach paper about what it means if someone is linking to a scholarly paper via social media."

Added 12 February 2012 Hyeon-Eui Kim, Xiaoqian Jiang, Jihoon Kim, Lucila Ohno-Machado (2011)
Trends in biomedical informatics: most cited topics from recent years
Journal of the American Medical Informatics Association, 18 (Suppl 1), 01 December 2011
info:pmid/22180873 | info:doi/10.1136/amiajnl-2011-000706
Abstract: Biomedical informatics is a young, highly interdisciplinary field that is evolving quickly. It is important to know which published topics in generalist biomedical informatics journals elicit the most interest from the scientific community, and whether this interest changes over time, so that journals can better serve their readers. It is also important to understand whether free access to biomedical informatics articles impacts their citation rates in a significant way, so authors can make informed decisions about unlock fees, and journal owners and publishers understand the implications of open access. The topics and JAMIA articles from years 2009 and 2010 that have been most cited according to the Web of Science are described. To better understand the effects of free access in article dissemination, the number of citations per month after publication for articles published in 2009 versus 2010 was compared, since there was a significant change in free access to JAMIA articles between those years. Results suggest that there is a positive association between free access and citation rate for JAMIA articles.

Added 12 February 2012; updated 4 March 2013 Sears, J. R. (2011)
Data Sharing Effect on Article Citation Rate in Paleoceanography
American Geophysical Union, Fall Meeting 2011
Abstract: The validation of scientific results requires reproducible methods and data. Often, however, data sets supporting research articles are not openly accessible and interlinked. This analysis tests whether open sharing and linking of supporting data through the PANGAEA data library measurably increases the citation rate of articles published between 1993 and 2010 in the journal Paleoceanography as reported in the Thomson Reuters Web of Science database. The 12.85% (171) of articles with publicly available supporting data sets received 19.94% (8,056) of the aggregate citations (40,409). Publicly available data were thus significantly (p=0.007, 95% confidence interval) associated with about 35% more citations per article than the average of all articles sampled over the 18-year study period (1,331), and the increase is fairly consistent over time (14 of 18 years). This relationship between openly available, curated data and increased citation rate may incentivize researchers to share their data.
See also
Michael Diepenbroek, Data Sharing Effect on Article Citation Rate in Paleoceanography, KomFor blog, November 27, 2011. Includes data plot.

Added 25 November 2011 Henneken, E. and Accomazzi, A. (2011)
Linking to Data - Effect on Citation Rates in Astronomy
arXiv.org > cs > arXiv:1111.3618, 15 Nov 2011. In Proceedings of ADASS XXI (Astronomical Data Analysis Software & Systems), Paris, 6-10 November 2011
From the Abstract: Is there a difference in citation rates between articles that were published with links to data and articles that were not? In this presentation we will show this is indeed the case: articles with links to data result in higher citation rates than articles without such links.
See also
Added 06 July 2011 Linking to Data - Effect on Citation Rates in Astronomy
Meters, Metrics and More, 03 Jun 2011
Extracts: Using the data holdings of the SAO/NASA Astrophysics Data System, our analysis shows that articles with data links are indeed cited more than articles without these links - for this data set, articles with data links acquired 20% more citations (compared to articles without these links).

Added 25 November 2011 Xia, J., Wilhoite, S. K. and Myers, R. L. (2011)
A librarian-LIS faculty divide in open access practice
Journal of Documentation, 67 (5), 791-805 (2011)
info:doi/10.1108/00220411111164673
(Subscription access required) From the Abstract: This paper measures the OA availabilities and citations of scholarly articles from 20 top-ranked LIS journals published in 2006.

Added 25 November 2011 Henneberger, S. (2011)
Entwicklung einer Analysemethode für Institutional Repositories unter Verwendung von Nutzungsdaten (Development of an analytical method for Institutional Repositories using usage data)
Thesis, edoc-Server der Humboldt-Universität zu Berlin, 31 Oct 2011
From the English abstract: Download data are the subject of scientific investigations, in which the concept of the Citation Impact is applied to the rate of use of a publication and the so-called Download Impact is formed. Analyzed with nonparametric methods, download data give information about the visibility of electronic publications on the Internet. These methods form the core of NoRA (Non-parametric Repository Analysis). The analytical method NoRA was successfully applied to data from Institutional Repositories of four universities. In each case, groups of publications were identified that differed significantly in their usage. Similarities in the results reveal factors that influence the usage data, which have not been taken into account previously. The presented results imply further applications of NoRA but also raise doubts about the value of download data of single publications.

Added 25 November 2011 Tarrant, D. (2011)
A Study of Early Indication Citation Metrics
PhD thesis, ECS EPrints Repository, University of Southampton, 24 Oct 2011
From the Abstract: Each new citation establishes a large number of co-citation relationships between that publication and older material whose citation impact is already well established. By taking advantage of this co-citation property, this thesis investigates the possibility of developing a metric that can provide an earlier indicator of a publications citation impact. This thesis proposes a new family of co-citation based impact measures, describes a system to evaluate their effectiveness against a large citation database, and justifies the results of this evaluation against an analysis of a diverse range of research metrics.

Added 25 November 2011 Yuan, S. and Hua, W. (2011)
Scholarly impact measurements of LIS open access journals: based on citations and links
The Electronic Library, 29 (5), 682, 2011
(Subscription access required) From the Abstract: The study selected 97 LIS OA journals as a sample and measured their scholarly impact on the basis of citations and links. The citation counts in WoS, coverage in LISA, Web links, WIFs and Page Rank of the journals are retrieved and calculated, and correlations between citation counts, links, pages, WIFs, and Page Rank are also analyzed. The results indicate that LIS OA journals have become a significant component of the scholarly communication system.

Added 25 November 2011 Priem, J., Piwowar, H. and Hemminger, B. (2011)
Altmetrics in the wild: An exploratory study of impact metrics based on social media
Poster at Metrics 2011: Symposium on Informetric and Scientometric Research, New Orleans, LA, 12 October
Extracts: As growing numbers of scholars publicly read, bookmark, share, discuss, and rate using online tools, these invisible impacts are beginning to be seen. Because measurements of these new traces may inform alternatives to traditional citation metrics, they been dubbed altmetrics. The goal of this study is to better understand the potential of altmetrics. We gathered altmetrics for a large sample of scholarly articles all 24,334 articles published by the Public Library of Science (PLoS) before December 23, 2010.

Added 25 November 2011 Wang, M.-L. (2011)
The impact of open access journals on library and information scientists' research in Taiwan
Universiti Teknologi Mara Digital Repository, 07 Oct 2011. In Asia-Pacific Conference On Library & Information Education & Practice 2011 (A-LIEP2011), 22-24 June 2011, Malaysia
From the Abstract: the objectives of the study is to explore the scholarly productivity of LIS scholars in Taiwan, to find out what articles they publish and OA articles as a percentage of all titles, and to calculate the mean citation rate of open access articles and articles not freely available online. To determine whether a difference in research impact existed, two research impact indicators were used, that is, open access articles as a percentage of all published titles and mean citation rate of open access articles and those not freely available online. Data on published articles with citation counts by the LIS scholars in Taiwan from 2000 to 2009 was collected from the ACI Database and Social Science Citation Index Database. The study shows that for 72 LIS scholars who were subjects of the investigation, 64 of them had published 745 articles within the previous ten years: 679 articles in Chinese and 66 articles in English; 499 of these were OA articles, and 264 were non-OA articles; OA articles constituted 66.98% of the total number of academic articles. The mean citation rate of OA versus non-OA article citation was 1.29.

Added 25 November 2011 Chuanfu Chen, Yuan Yu, Qiong Tang, Kuei Chiu, Yan Rao, Xuan Huang and Kai Sun (2011)
Assessing the authority of free online scholarly information
Scientometrics, 02 Oct 2011
(Subscription access required. Online preview.) From the Abstract: Using a modified version of Jim Kapouns Five criteria for evaluating web pages as framework, this research selected 32 keywords from eight disciplines, inputted them into three search engines (Google, Yahoo and AltaVista) and used Analytic Hierarchy Process to determine the weights. The first batches of results (web pages) from keyword searching were selected as evaluation samples (in the two search phases, the first 50 and 10 results were chosen, respectively), and a total of 3,134 samples were evaluated for authority based on the evaluation framework. The results show that the average authority value for free online scholarly information is about 3.63 (out of five), which is in the fair level (3 Z < 4) (Z is the value assigned to each sample). About 41% of all samples collected provide more authoritative scholarly information. Different domain names, resource types, and disciplines of free online scholarly information perform differently when scored in terms of authority. In conclusion, the authority of free online scholarly information has been unsatisfactory, and needs to be improved.

Added 25 November 2011 Davis, P. (2011)
Do discounted journal access programs help researchers in sub-Saharan Africa? A bibliometric analysis
eCommons@Cornell, 23 Sep 2011. In Learned Publishing, Vol. 24, No. 4, October 2011, pp. 287-298
Abstract: Prior research has suggested that providing free and discounted access to the scientific literature to researchers in low-income countries increases article production and citation. Using traditional bibliometric indicators for institutions in sub-Saharan Africa, we analyze whether institutional access to TEEAL (a digital collection of journal articles in agriculture and allied subjects) increases: 1) article production; 2) reference length; and 3) number of citations to journals included in the TEEAL collection. Our analysis is based on nearly 20,000 articlescontaining half a million referencespublished between 1988 and 2009 at 70 institutions in 11 African countries. We report that access to TEEAL does not appear to result in higher article production, although it does lead to longer reference lists (an additional 2.6 references per paper) and a greater frequency of citations to TEEAL journals (an additional 0.4 references per paper), compared to non-subscribing institutions. We discuss how traditional bibliometric indicators may not provide a full picture of the effectiveness of free and discounted literature programs.

Added 12 February 2012 Jeffrey Furman and Scott Stern (2011)
Climbing atop the Shoulders of Giants: The Impact of Institutions on Cumulative Research
American Economic Review, 101 (5), 1933-63, August 2011
From the Abstract: This paper assesses the impact of a specific institution, a biological resource center, whose objective is to certify and disseminate knowledge. We disentangle the marginal impact of this institution on cumulative research from the impact of selection, in which the most important discoveries are endogenously linked to research-enhancing institutions. Exploiting exogenous shifts of biomaterials across institutional settings and employing a difference-in-differences approach, we find that effective institutions amplify the cumulative impact of individual scientific discoveries. From the paper: Our empirical analysis focuses on whether articles associated with materials exogenously shifted into a BRC receive a boost in citations after their deposit into the BRC, controlling for article-specific fixed effects and fixed effects for article age and calendar year. Our setting allows us to evaluate both models that include a control sample and models that rely exclusively on variation in the timing and date of the treatment of the deposit of the biomaterial into the BRC. Both approaches provide evidence for the marginal impact of BRCs on subsequent knowledge; the post-deposit citation boost is estimated to be between 57 percent and 135 percent across different specifications. Empirical checks of our key identification assumptions reinforce our overall findings. We find that the marginal impact of BRC deposit is marginally higher for articles published in less prestigious journals and that the citation boost is concentrated in follow-on research articles involving more complex subject matter. (Paper extract from copy at: http://www.econ.tuwien.ac.at/hanappi/Lehre/Economic%20Policy/2012/Furman_2011.pdf)
See also these 2002 and 2006 papers of the same title by the same authors:
News articles on this paper:
Peter Dizikes, How research goes viral, MIT News, 10 January 2012: When things become more open, it's not simply that you get more research, but you get more diverse research, Stern notes.

Added 23 April 2012 Peter Ingwersen and Anita Elleby (2011)
Do Open Access Working Papers Attract more Citations Compared to Printed Journal Articles from the same Research Unit?
Royal School of Information and Library Science, Copenhagen, (2011). In Proceedings 13th International Conference of the International Society for Scientometrics & Informetrics, Durban, South Africa, 4-7 July 2011
Abstract: This paper presents the results of an empirical case study of the characteristics of citations received by 10 open access non-peer reviewed working papers published by a prestigious multidisciplinary, but basically social science research institute, compared to 10 printed peer reviewed journal articles published in the same year (2004) by the same institute and predominantly by the same authors. The study analyzes the total amount of citations and citation impact observed in Web of Science (WoS) and Google Scholar (GS) received during the five-year period 2004-09 (February) by the two publication types, the citation distributions over the individual sample publications and observed years as well as over external, institutional and personal self-citations. The institute concerned is the Danish Institute for International Studies (DIIS), Copenhagen. The results demonstrate that the open access working papers publicly accessible through the DIIS e-archive became far less cited than the corresponding sample of DIIS journal articles published in printed form. However, highly cited working papers have higher impact than the average of the lower half of cited articles. Citation time series show identical distinct patterns for the articles in WoS and GS and working papers in GS, more than doubling the amount of citations received through the latter source.
See also Open access working papers not good enough, ScienceNordic.com, December 7, 2011

Added 25 November 2011 McGreal, R. and Chen, N.-S. (2011)
AUPress: A Comparison of an Open Access University Press with Traditional Presses
Educational Technology & Society, 14 (3), 231-9 (2011)
Abstract: This study is a comparison of AUPress with three other traditional (non-open access) Canadian university presses. The analysis is based on the rankings that are correlated with book sales on Amazon.com and Amazon.ca. Statistical methods include the sampling of the sales ranking of randomly selected books from each press. The results of one-way ANOVA analyses show that there is no significant difference in the ranking of printed books sold by AUPress in comparison with traditional university presses. However, AUPress, can demonstrate a significantly larger readership for its books as evidenced by the number of downloads of the open electronic versions.

Added 18 August 2011 Davis, P. and Walters, W. (2011)
The impact of free access to the scientific literature: a review of recent research
Journal of the Medical Library Association, 99 (3), 208-217, July 2011
doi: 10.3163/1536-5050.99.3.008
From the Abstract: The paper reviews recent studies that evaluate the impact of free access (open access) on the behavior of scientists as authors, readers, and citers in developed and developing nations. It also examines the extent to which the biomedical literature is used by the general public. Researchers report that their access to the scientific literature is generally good and improving. For authors, the access status of a journal is not an important consideration when deciding where to publish. There is clear evidence that free access increases the number of article downloads, although its impact on article citations is not clear. Recent studies indicate that large citation advantages are simply artifacts of the failure to adequately control for confounding variables. The effect of free access on the general public's use of the primary medical literature has not been thoroughly evaluated.

Added 06 July 2011 Shafi, Sheikh Mohammad and Bhat, Mohammad Haneef (2011)
The Impact of Open Access Contributions: Developed and Developing World Perspectives
Proceedings of the 15th International Conference on Electronic Publishing, Istanbul, Turkey, 22 Jun 2011
From the Abstract: The study explores the research impact of Open Access research articles across the globe with a view to test the hypothesis that OA research contributions emanating from developing countries receive equal citations (subsequently resultant research impact) as those from the developed world. The study covers 5639 research articles from 50 Open Access DOAJ based Medical Sciences journals covering the period from 2005 to 2006. The research articles from the developed countries receive higher number of citations (subsequently resultant research impact) compared to those of the developing world. The study may help and pave way for framing policies and strategies to increase the impact of research in the developing world.

Added 06 July 2011 Yan, K.-K. and Gerstein, M. (2011)
The Spread of Scientific Information: Insights from the Web Usage Statistics in PLoS Article-Level Metrics
PLoS ONE, 6 (5), 16 May 2011
info:doi/10.1371/journal.pone.0019917
From the Abstract: In this work, we focus on a community of scientists and study, in particular, how the awareness of a scientific paper is spread. Our work is based on the web usage statistics obtained from the PLoS Article Level Metrics dataset compiled by PLoS. We found that the spread of information displays two distinct decay regimes: a rapid downfall in the first month after publication, and a gradual power law decay afterwards. We identified these two regimes with two distinct driving processes: a short-term behavior driven by the fame of a paper, and a long-term behavior consistent with citation statistics.

Added 06 July 2011 Xia, J. (2011)
Positioning Open Access Journals in a LIS Journal Ranking
College & Research Libraries, 16 May 2011
From the Introduction: some OA journals have successfully built reputations, attracting high-quality articles and sizable numbers of citations. This research is an attempt to add selected OA journals to the journal quality rankings using library and information science (LIS) as an example.

Added 05 May 2011 Sandra Miguel, Zaida Chinchilla-Rodriguez, Félix de Moya-Anegón (2011)
Open access and Scopus: A new approach to scientific visibility from the standpoint of access
Journal of the American Society for Information Science and Technology, published online: 11 April 2011
From the Abstract: This study shows a new approach to scientific visibility from a systematic combination of four databases: Scopus, the Directory of Open Access Journals, Rights Metadata for Open Archiving (RoMEO)/Securing a Hybrid Environment for Research Preservation and Access (SHERPA), and SciMago Journal Rank, and provides an overall, global view of journals according to their formal OA status. The results primarily relate to the number of journals, not to the number of documents published in these journals, and show that in all the disciplinary groups, the presence of green road journals widely surpasses the percentage of gold road publications. The benefits of OA on visibility of the journals are to be found on the green route, but paradoxically, this advantage is not lent by the OA, per se, but rather by the quality of the articles/journals themselves regardless of their mode of access.

Added 05 May 2011 Liu Xue-li, Fang Hong-ling and Wang Mei-ying (2011)
Correlation between Download and Citation and Download-citation Deviation Phenomenon for Some Papers in Chinese Medical Journals
Serials Review, Vol. 37, No. 3, September 2011, 157-161, available online 7 April 2011
From the Abstract: The authors collected the numbers of citations and downloads from 2005 to 2009 of papers in five Chinese general ophthalmological journals published in 2005 from the Chinese Academic Journals Full-text Database and the Chinese Citation Database in Chinese National Knowledge Infrastructure (CNKI) to determine the correlation between download and citation and the peak time of download frequency (DF). The citations from 2000 to 2009 of papers published in 2000 were collected to determine the peak time of citation frequency (CF) of medical papers. There is a highly positive correlation between DF and CF (r = 4.91, P = 0.000).

Added 04 April 2011 Davis, P. (2011)
Open access, readership, citations: a randomized controlled trial of scientific journal publishing
The FASEB Journal (Journal of the Federation of American Societies for Experimental Biology), 30 Mar 2011
info:doi/10.1096/fj.11-183988
Abstract: Does free access to journal articles result in greater diffusion of scientific knowledge? Using a randomized controlled trial of open access publishing, involving 36 participating journals in the sciences, social sciences, and humanities, we report on the effects of free access on article downloads and citations. Articles placed in the open access condition (n=712) received significantly more downloads and reached a broader audience within the first year, yet were cited no more frequently, nor earlier, than subscription-access control articles (n=2533) within 3 yr. These results may be explained by social stratification, a process that concentrates scientific authors at a small number of elite research universities with excellent access to the scientific literature. The real beneficiaries of open access publishing may not be the research community but communities of practice that consume, but rarely contribute to, the corpus of literature.
See also this author's earlier dissertation.
News articles on this paper:
Corbyn, Z., Open access articles not cited more, finds study, The Great Beyond: Nature news blog, 01 Apr 2011: "We do leave open the possibility that there is a real citation effect as a result of self archiving but that we simply do not have the statistical power to detect it," says Davis. (In comments appended to this article Davis says: "the piece is not balanced. Zoe focuses on the weaknesses of the study and not its strengths")
Wieder, B., Open Access Does Not Equal More Citations, Study Finds, Wired Campus, Chronicle of Higher Education, April 1, 2011: Mr. Davis says he doesn't see his study as a blow to open access - if anything, he thinks it calls into question the wisdom of looking only at citation counts to measure the impact of a journal article, particularly given the ease of tracking article downloads online. "Twenty years ago, there was no way of measuring readership," he says.

Comment on this paper:
Various, Re: Open access, readership, citations: a randomized controlled trial of scientific journal publishing, SIGMETRICS Archives (follow Topic thread), from 30 Mar 2011: Palmer, C. > Does free access to journal articles result in greater diffusion of scientific knowledge? /> "I'm confused. Your article does not answer this overly-broad question. Why do you pose it here?" Davis, P. "We extend our measurements to include article downloads (abstract, fulltext and pdf) as well as visitors (as measured by unique IP addresses)." Palmer, C. "I like the extended measurements and the discussion, and I think I did understand your operationalization on the first read, but I'm still confused as to your answer to your own question." Davis, P. "I think the answer is apparent: "Yes" if one looks at readership, but "No" if one looks at citations. I see the world as a more complicated and nuanced place than through the lens of advocacy."
Harnad, S., On Methodology and Advocacy: Davis's Randomization Study of the OA Advantage, Open Access Evangelism, March 31. 2011: Still no self-selected self-archiving control, hence no basis for the conclusions drawn (to the effect that the widely reported OA citation advantage is merely an artifact of a self-selection bias toward self-archiving the better, hence more citeable articles -- a bias that the randomization eliminates). The methodological flaw, still uncorrected, has been pointed out before. Readers can be trusted to draw their own conclusions as to whether this study, tirelessly touted as the only methodologically sound one to date, is that -- or an exercise in advocacy.
Bruggeman, D., Impact of Open Access on Citations Still Mixed, Pasco Phronesis blog, April 2, 2011: a mixed record of citation impacts should be no surprise to those who have followed this research area. The headline-level synopsis of this and other studies attempting to discern the impacts of open access research obscure a multitude of methodological concerns. They also downplay significant differences found when breaking the data down by field, country, or other factors.
Harnad, S., "The Sole Methodologically Sound Study of the Open Access Citation Advantage", Open Access Evangelism, April 2. 2011, in response to Wieder (ChronHE): The greatest growth potential for open access today is through open access self-archiving mandates adopted by the universal providers of research: the researchers' universities, institutions and funders (e.g., Harvard and MIT). See the ROARMAP registry of open-access mandates. Universities adopt open access mandates in order to maximize their research impact. The large body of evidence, in field after field, that open access increases citation impact, helps motivate universities to mandate open access self-archiving of their research output, to make it accessible to all its potential users -- rather than just those whose universities can afford subscription access -- so that all can apply, build upon and cite it. Davis says he does not see why the inferences he attempts to make from his results are not welcomed by researchers. These inferences are not welcomed because they are based on flawed methodology and insufficient statistical power and yet they are being widely touted (particularly by the publishing industry lobby) as being the sole methodologically sound test of the open access citation advantage! Ignore the many positive studies. They are all methodologically flawed. The definitive finding, from the sole methodologically sound study, is negative. So there's no access problem, researchers have all the access they need -- and hence there's no need to mandate open access self-archiving. No, this string of inferences is not a "blow to open access" -- but it would be if it were taken seriously.
Added 23 April 2012 David Crotty, Gaming the System: Do Promises of Citation Advantage Go Too Far? Scholarly Kitchen, Apr 5, 2011: The Scholarly Kitchen's own Phil Davis (consider this your conflict-of-interest statement) attempts to do away with selection bias by looking at a randomized set of papers. The access status of the articles in the study (OA or under subscription-access control) was determined at random, not by author or editorial choice. The randomization is important here, as it allows Davis to compare equal groups of articles and control for other sources of bias. The study showed that OA articles were cited no more frequently, nor earlier, than subscription-access control articles within 3 years. Davis study shows that OA articles are more widely read than non-OA articles, and this is a significant benefit of OA publishing. If the goal of the OA movement is to create a scientific literature with a broader reach, then it is succeeding admirably."

Added 04 April 2011 Donovan, J. M. and Watson, C. A. (2011)
Citation Advantage of Open Access Legal Scholarship
Social Science Research Network (SSRN), 5 March 2011. In Law Library Journal, 103 (4), Fall 2011, 553-573 http://www.aallnet.org/main-menu/Publications/llj/Vol-103/Fall-2011/2011-35.pdf. Also in UKnowledge, University of Kentucky, 2011 http://works.bepress.com/james_donovan/64/
Abstract: To date, there have been no studies focusing exclusively on the impact of open access on legal scholarship. We examine open access articles from three journals at the University of Georgia School of Law and confirm that legal scholarship freely available via open access improves an articles research impact. Open access legal scholarship which today appears to account for almost half of the output of law faculties can expect to receive 50% more citations than non-open access writings of similar age from the same venue.

Added 15 February 2011 Xu, L., Liu, J. and Fang, Q. (2011)
Analysis on open access citation advantage: an empirical study based on Oxford open journals
iConference '11, Proceedings of the 2011 iConference, Seattle, 11 February 2011
Abstract: This study takes 12,354 original research articles which were published in 93 Oxford Open journals in 2009 as a sample, and carries out statistic analyses on the citation frequency that these articles have received by July 2010 to validate 3 hypotheses: (1) there is citation advantage for open access articles (OACA) published in Oxford Open journals over the non-OA ones; (2) OACA varies with disciplines; (3) there is some correlation between the impact factors (IFs) of Oxford Open journals and the OACA of their open access articles. This study discovers that: there exists OACA for open access articles, in this case 138.87% higher over non-OA ones; different subjects have different OACAs, and Humanities journals in Oxford Open have even a negative OACA; Oxford Open journals with lower IFs have stronger OACAs than those with higher IFs.

Added 15 February 2011 McCabe, M. J. and Snyder, C. M. (2011)
Did Online Access to Journals Change the Economics Literature?
Social Science Research Network, SSRN, January 23, 2011
Abstract: Does online access boost citations? The answer has implications for issues ranging from the value of a citation to the sustainability of open-access journals. Using panel data on citations to economics and business journals, we show that the enormous effects found in previous studies were an artifact of their failure to control for article quality, disappearing once we add fixed effects as controls. The absence of an aggregate effect masks heterogeneity across platforms: JSTOR boosts citations around 10%; ScienceDirect has no effect. We examine other sources of heterogeneity including whether JSTOR benefits "long-tail" or "superstar" articles more.
See also Kolowich, S., Questioning the 'Citation Advantage', Inside Higher Education, February 10, 2011: investigates reaction to this paper. "While McCabe and Snyder actually studied the effect of economics and business articles being available online as opposed to just in print -- not the effect of articles being online and free -- they nevertheless believe that their findings cast doubt on the supposed citation advantage of open-access articles, because, they contend, their study measures whether ease of access affects citation volume. ... contrary to its provocative assertion about the lack of evidence that free online access performs better, their paper does not address the citation advantage of free versus not free, Harnad says, and therefore cannot convincingly refute studies that do."

Comment on this paper:
Davis, P., Online Access and Citations A Spurious Relationship, Economists Say, the scholarly kitchen, Feb 8, 2011: The main contribution of the McCabe and Snyder paper is their explanation for scores of initial papers reporting huge access-citation effects i.e., they are artifacts of improper statistical analysis. The fact that there are many of these poor studies in the literature, or that their claims have achieved consensus among certain like-minded individuals, does not make for good science, nor does it help to inform good science policy." See reader responses attached to this post, some extracts below.
Ottaviani, J., Feb 8, 2011: Having read it, their findings don't appear to talk specifically about open access, while the conclusion of your summary does. Can you point me to where open access is treated independently from online access, or as a distinct subset of it, in their analysis?
Davis, P., Feb 8, 2011: You are correct in that M&S focus entirely on online access. Their manuscript needs to be read in context of two prior papers by James Evans, who reported significant online and open access effects using a similar methodology.
Ottaviani, J., Feb 9, 2011: M&S compared the effects of expensive, location-based access (print) to more convenient but still expensive and affiliation-based access (online) on citation patterns. Extending their conclusion to citation pattern differences between expensive, restricted online access and free, unrestricted access (open) is a big leap ...
Harnad, S., Re: More on Open Access citations, liblicense, 10 February 2011: This has nothing whatsoever to do with Open Access. OA is about providing access to those who don't have subscription access; this paper is about providing online access to those who had subscription access before, but on paper, and now have online access. Moreover, it is in a field (economics) where there is wide posting of OA preprints (not taken into account at all).
McCabe, M. J., Comments on Questioning the 'Citation Advantage', February 10, 2011: Yes, we only test online versus print, and not OA versus online for example, but the empirical flaws in the online versus print and the OA versus online literatures are fundamentally the same: the failure to properly account for selection bias. So, using the same technique in both cases should produce similar results.
The following response to comments by McCabe above can be found appended to the same article or in this separate source:
Harnad, S., Critique of McCabe & Snyder: Online not= OA, and OA not= OA journal, Open Access Archivangelism, February 13. 2011: Unfortunately this is not very convincing. Flaws there may well be in the methodology of studies comparing citation counts before and after the year in which a journal goes online. But these are not the flaws of studies comparing citation counts of articles that are and are not made OA within the same journal and year. If "selection bias" refers to authors' bias toward selectively making their better (hence more citeable) articles OA, then this was controlled for in the comparison of self-selected vs. mandated OA, by Gargouri et al (2010) (uncited in M&S)
- It is ironic that M & S draw their conclusions about OA in economic terms (and, predictably, as their interest is in modelling publication economics) in terms of the cost/benefits, for an author, of paying to publish in an OA journal, concluding that since they have shown it will not generate more citations, it is not worth the money. But the most compelling findings on the OA citation advantage come from OA author self-archiving (of articles published in non-OA journals), not from OA journal publishing. Those are the studies that show the OA citation advantage, and the advantage does not cost the author a penny!

Added 04 April 2011 Saadat, R. and Shabani, A. (2011)
Investigating the Citations Received by Journals of Directory of Open Access Journals from ISI Web of Sciences Articles
International Journal of Information Science and Management, 9 (1), 57-74, January 2011
From the Abstract: In this research, the citations received by DOAJs journals from the ISI Web of Sciences articles in 2003 to 2008 were studied and compared. The citations received by the journals in five fields (Arts & Humanities, Social Sciences, Pure Sciences, Technology & Engineering, and Health & Medical Sciences) as well as the difference among the citations received by DOAJs journals in the above- mentioned five fields were examined. The research method is citation analysis and the research data have been collected by means of Cited Reference Search in the ISI Web of Science. The English-language journals in DOAJ were chosen, and no sampling was used. Findings showed that out of 2953 journals, 321 journals (10.87%) received citations, and the total citations received by these journals were 19050 with the mean of 6.45 per journal; the journals in Pure Sciences received most citations (10116 citations, equal to 53.1%), and the ones in Arts & Humanities received the least citations (701 citations, equal to 3.68%).

Added 15 February 2011 Lee, K., Brownstein, J. S., Mills, R. G., Kohane, I. S. (2010)
Does Collocation Inform the Impact of Collaboration?
PLoS ONE, 5 (12), e14279, 15 Dec 2010
From the Abstract: Despite the positive impact of emerging communication technologies on scientific research, our results provide striking evidence for the role of physical proximity as a predictor of the impact of collaborations. From the Discussion: There have been numerous articles that reported Open Access publications have higher chance to be cited more. It may be that publications in Open Access journals have higher citation, which may not necessarily be related to collaboration and collocation. However, its impact on our results is uncertain as there are also growing number of articles that are reporting no evidence of Open Access advantage in different disciplines.

Added 15 February 2011 Xia, J., Myers, R. L. and Wilhoite, S. K. (2010)
Multiple open access availability and citation impact
Journal of Information Science, 37 (1): 19-28, published online 10 Dec 2010
Abstract: This research examines the relationship between multiple open access (OA) availability of journal articles and the citation advantage by collecting data of OA copies and citation numbers in 20 top library and information science journals. We discover a correlation between the two variables; namely, multiple OA availability of an article has a positive impact on its citation count. The statistical analysis reveals that for every increase in the availability of OA articles, citation numbers increase by 2.348.

Added 6 December 2010 Davis. P. (2010)
Does Open Access Lead to Increased Readership and Citations? A Randomized Controlled Trial of Articles Published in APS Journals
The Physiologist, 53 (6), December 2010
Extracts. Introduction: In order to isolate the effect of access on readership and citations, we conducted a randomized controlled trial of open access publishing on articles published electronically in 11 APS journals. This report details the findings three years after the commencement of the experiment. Discussion: The results of this experiment suggest that providing free access to the scientific literature may increase readership (as measured by article downloads) and reach a larger potential audience (as measured by unique visitors), but have no effect on article citations. These results are consistent with an earlier report of the APS study after one year and the results of other scientific journals after two years. The fact that we observe an increase in readership and visitors for Open Access articles but no citation advantage suggests that scientific authors are adequately served by the current APS model of information dissemination, and second, that the additional readership is taking place outside this core research community.

Comment on this paper:
From ASIST SIGMETRICS email listserv, Re: Davis study (was: Open access publishing, article downloads and citations at 3years), from 23 November 2010. Use the Next in Topic link to follow the debate. Extracts:
Davis, P. (the author): Critics of our open access publishing experiment (read: Stevan Harnad) have expressed skepticism that we were too eager to report our findings and should have waited between 2 and 3 years. All of the articles in our study have now aged 3-years and we report that our initial findings were robust: articles receiving the open access treatment received more article downloads but no more citations.
Harnad, S., Phil Davis's dissertation results are welcome and interesting, and include some good theoretical insights, but insofar as the OA Citation Advantage is concerned, the empirical findings turn out to be just a failure to replicate the OA Citation Advantage, almost certainly due to the small sample size as well as the short time-span.
Davis, P., Your new interest in sample sizes implies -- although you don't seem willing to admit -- that an OA citation advantage is much, much smaller than initially reported. Early studies (including yours) estimated the citation effect to be somewhere between 50% and 500% -- ranges that should be easily detectable with smaller sample sizes such as our study. By focusing on the fact that I do not have the statistical power to detect very small differences is really an admission that an OA citation advantage -- if one truly exists -- can be largely explained by other theories (e.g. self-selection) and that the part attributable to free access is very small indeed.
Harnad, S., I've always been interested in sample sizes. That's why all of our studies have been based on samples that have been orders of magnitude bigger than (for example) yours. But let's not confuse effect-size and the sample-size needed to detect a statistically significant effect; that's not a question about effect size but about variability. The size of the OA citation advantage does indeed vary considerably (from field to field, year to year, and sample to sample). Overall, across all fields of scientific and scholarly research produced by universities and funded by funders, that adds up to a sizeable benefit to research, researchers, their institutions, their funders, and the public that funds the funders and for whose benefit the research is being done, and funded -- a benefit that is worth having, by mandating OA. That implication is very clear -- and it certainly is not the implication you cite in your December summary in the APS house journal, The Physiologist: "The fact that we observe an increase in readership and visitors for Open Access articles but no citation advantage suggests that scientific authors are adequately served by the current APS model of information dissemination." What your findings show is that there was no OA citation advantage in your (small) sample. Point taken. But the interpretation is a mighty stretch, if not an exercise in APS spin.
Waltman, L., Phil kindly provided me with the data of his study. In my view, Phil has convincingly shown that, at least for the journals and the time intervals he studied, there is no meaningful OA citation advantage but also (see later post by Waltman) that an OA citation advantage of reasonable size is unlikely to exist in the underlying population.
Harnad, S., It depends on what you mean by "the underlying population." If you mean that general population of articles, in multiple different fields, tested by multiple independent investigators, reporting a significant (and sometimes quite sizeable) OA citation advantage (with the exception of a very small number of negative or null outcomes), then Phil's study certainly has *not* shown "that an OA citation advantage of reasonable size is unlikely to exist" in *that* underlying population. It would take a null meta-analysis, not just one null outcome, to be able to show that. (Otherwise any repeatedly observed effect could be dismissed on the basis of one non-replication!) We too did a test of the self-selection hypothesis -- on a much larger sample across more fields and a longer time interval -- and we not only found "an OA citation advantage of reasonable size" for self-selected OA, but we found that the advantage was the same size for mandated OA. We accordingly conclude that "an OA citation advantage of reasonable size is likely to exist in the underlying population" if you test for it, and your sample is big enough and long enough -- except perhaps in Phil's sample of (mostly APS) journals...
Davis, P., Let's move to your new concern about generalizability: While I can't claim negative results across all fields and across all times, our randomized controlled trials (RCTs) did involve 36 journals produced by 7 different publishers in the medical, biological, and multi-disciplinary sciences, plus the social sciences and humanities. Yet, if you are basing your comparison solely on number of journals and number of articles, then you are completely missing the rationale for conducting the RCTs in the first place
Harnad, S., The many published comparisons are based on comparing OA and non-OA articles within the same journal and year. That's the studies that are simply testing whether there is an OA citation advantage. But the comparison you are talking about is the comparison between self-selected and imposed OA. Your study has shown that in your sample (consisting of OA imposed by randomization), there is no OA citation advantage (only an OA download advantage). But it has not shown that there is any OA self-selection advantage either. Without that, there is only the non-replication of the OA citation advantage.

Added 18 August 2011 Düzyol, G., Taskin, Z. and Tonta, Y. (2010)
Mapping the Intellectual Structure of Open Access Field Through Co-citations
E-LIS, 29 November 2010
In IFLA Satellite Pre-conference: Open Access to Science Information Trends, Models and Strategies for Libraries, 6-8 August 2010, Crete (Greece)
also at http://yunus.hacettepe.edu.tr/~tonta/yayinlar/tonta-duzyol-taskin-oa.pdf
From the Abstract: This paper maps the intellectual structure of open access based on 281 articles that appeared in professional literature on the topic between 2000 and 2010. Using bibliometric and co-citation analyses, co-citation patterns of papers are visualized through a number of co-citation maps. CiteSpace was used to analyze and visualize co-citation maps. Maps show major areas of research, prominent articles, major knowledge producers and journals in the field of open access. The letter written by Steven Lawrence (Free online availability substantially increases a papers impact, 2001) appears to be the most prominent source as it was cited the most. The preliminary findings show that open access is an emerging research field. Findings of this study can be used to identify landmark papers along with their impact in terms of providing different perspectives and engendering new research areas.

Added 6 December 2010 Davis. P. (2010)
Access, Readership, Citations: A Randomized Controlled Trial Of Scientific Journal Publishing
eCommons@Cornell, 20 October 2010
From the abstract: This dissertation explores the relationship of Open Access publishing with subsequent readership and citations. It reports the findings of a randomized controlled trial involving 36 academic journals produced by seven publishers in the sciences, social sciences and humanities. At the time of this writing, all articles have aged at least two years. Articles receiving the Open Access treatment received significantly more readership (as measured by article downloads) and reached a broader audience (as measured by unique visitors), yet were cited no more frequently, nor earlier, than subscription-access control articles. A pronounced increase in article downloads with no commensurate increase in citations to Open Access treatment articles may be explained through social stratification, a process which concentrates scientific authors at elite, resource-rich institutions with excellent access to the scientific literature. For this community, access is essentially a non-issue.

Added 17 Feb 2010, updated 18 Oct 2010 Gargouri, Y., Hajjem, C., Lariviere, V., Gingras, Y., Brody, T., Carr, L. and Harnad, S. (2010)
Self-Selected or Mandated, Open Access Increases Citation Impact for Higher Quality Research
PLoS ONE 5(10): e13636, October 18, 2010, doi:10.1371/journal.pone.0013636
Also in ECS EPrints, 10 Feb 2010, http://eprints.ecs.soton.ac.uk/18493/ (this version includes the paper and full supplemental materials, including further analyses and responses to comments and feedback), and in arXiv, arXiv:1001.0361v2 [cs.CY], 3 Jan 2010
Abstract
Background. Articles whose authors have supplemented subscription-based access to the publisher's version by self-archiving their own final draft to make it accessible free for all on the web (Open Access, OA) are cited significantly more than articles in the same journal and year that have not been made OA. Some have suggested that this OA Advantage may not be causal but just a self-selection bias, because authors preferentially make higher-quality articles OA. To test this we compared self-selective self-archiving with mandatory self-archiving for a sample of 27,197 articles published 20022006 in 1,984 journals.
Methdology/Principal Findings. The OA Advantage proved just as high for both. Logistic regression analysis showed that the advantage is independent of other correlates of citations (article age; journal impact factor; number of co-authors, references or pages; field; article type; or country) and highest for the most highly cited articles. The OA Advantage is real, independent and causal, but skewed. Its size is indeed correlated with quality, just as citations themselves are (the top 20% of articles receive about 80% of all citations).
Conclusions/Significance. The OA advantage is greater for the more citable articles, not because of a quality bias from authors self-selecting what to make OA, but because of a quality advantage, from users self-selecting what to use and cite, freed by OA from the constraints of selective accessibility to subscribers only. It is hoped that these findings will help motivate the adoption of OA self-archiving mandates by universities, research institutions and research funders.

Comment on this paper:

Added 6 Dec 2010 Comments below refer to the PLoS ONE publication
Howard, J., Is There an Open-Access Citation Advantage? The Chronicle of Higher Education, 19 Oct 2010:
Seeks to reignite the earlier debate around the preprint of the new PLoS ONE paper. And succeeds - see reader responses attached to the article, some extracts below.
Harnad, S., Correlation, Causation, and the Weight of Evidence, Open Access Archivangelism, 20 Oct 2010: One can only speculate on the reasons why some might still wish to cling to the self-selection bias hypothesis in the face of all the evidence to date. The straightforward causal relationship is the default hypothesis, based on both plausibility and the cumulative weight of the evidence. Hence the burden of providing counter-evidence to refute it is now on the advocates of the alternative.
sk_griffhoven, October 20, 2010: The authors were unable to control for institutional effects in their model. While deposit mandates might be responsible for the results they report, they might not, and I dont see how mandates would outperform self-selection. Most importantly, there is no basis for making a causal claim. I agree with Philip David: the authors greatly overstate their results.
stevanharnad, October 21, 2010: The causal claim is not that mandated OA out-performs self-selected OA, but that self-selected OA does *not* out-perform mandated OA, hence OA is causal.
signofthefourwinds, October 21, 2010: It doesnt make sense that researchers suddenly give up their habit of consulting certain databases to go search in Google Scholar. What user behavior change accounts for the OA advantage?
stevanharnad, October 22, 2010: The OA Advantage is not just, or primarily, a convenience or laziness effect (though some of that no doubt contributes to it too): It is not that scholars have become sloppy, relying on google scholar instead of consulting more established databases. It is that when their institution cannot afford access to articles they need, they must make do with only those of them that they can access for free online.
Patrick Chardenet, October 22, 2010: I dont think that the problem is to know if Open Access reinforces or not the number of citations. It is rather a question of knowing if the measurement of science by the measurement of the number of citations has an interest for the scientific development.
stevanharnad, October 22, 2010: In a nutshell, citations are not the goal of research; the goal is that the research should be read, used and built upon, in further research and applications. And citations are a measure of that. But for research to be read, used and built upon, it has to be accessible. That is why and how OA increases citations.
Fenner, M., New in PLoS ONE: Citation rates of self-selected vs. mandated Open Access, PLoS Blogs, Gobbledygook, 19 Oct 2010: "I feel that the paper comes a little short. Yes, they did a very detailed analysis of the citation behavior, and take into account important cofactors. But the reader is left with the impression that mandatory self-archiving of post-prints in institutional repositories is the only reasonable Open Access strategy, and the introduction and discussion accordingly leave out some important arguments." Notable for the substantive discussion that follows between the blogger (Fenner) and one of the principal authors of the paper (Harnad).
Harnad, S., Comparing OA and Non-OA: Some Methodological Supplements, Open Access Archivangelism, 19 Oct 2010. Responds to Fenner: "If we have given "the impression that mandatory self-archiving of post-prints in institutional repositories is the only reasonable Open Access strategy," then we have succeeded in conveying the implication of our findings."

Comments below refer to the preprint
Davis, P., Does a Citation Advantage Exist for Mandated Open Access Articles? the scholarly kitchen, Jan 7, 2010; "Gargouri reports that institutionally-mandated OA papers received about a 15% citation advantage over self-selected OA papers, which seems somewhat counter-intuitive. If better articles tend to be self-archived, their reasoning goes, we should expect that papers deposited under institutional-wide mandates would under-perform those where the authors select which articles to archive. The authors of this paper deal, rather unscientifically, with this inconvenient truth with a quick statistical dismissal that their finding "might be due to chance or sampling error. In sum, this paper tests an interesting testable hypothesis on whether mandatory self-archiving policies are beneficial to their authors in terms of citations. Their unorthodox methodology, however, results in some inconsistent and counter-intuitive results that are not properly addressed in their narrative."
The following were among the comments added to the above blog by Davis.
Harnad, S., Jan 7, 2010: "Mandated OA Advantage? Yes, the fact that the citation advantage of mandated OA was slightly greater than that of self-selected OA is surprising, and if it proves reliable, it is interesting and worthy of interpretation. We did not interpret it in our paper, because it was the smallest effect, and our focus was on testing the Self-Selection/Quality-Bias hypothesis, according to which mandated OA should have little or no citation advantage at all, if self-selection is a major contributor to the OA citation advantage."
Gaule, P., Jan 7, 2010: "the paper does not appear to include controls for institutions of the authors of the control sample. This is particularly worrisome when comparing papers originating from CERN which arguably does cutting edge physics to the control papers. The key issue in this paper seems to be interpreting the mandated open access versus self-selected open access. The authors find and point out that the mandates actually result in compliance of around 60%. However, they have little to say on what is going on here and why papers end up in the compliant group or not. I am not sure what conclusions can be inferred from this comparison of two types of self-selection, at least one of which is not well understood."
Harnad, S., Jan 8, 2010: "(2) THE SPECIAL CASE OF CERN: With so few institutional mandates, its not yet possible to control for institutional quality. But CERN is indeed a special case; when it is removed, however, it does not alter the pattern of our results. (3) SELECTIVE COMPLIANCE? Mandate compliance is not yet 100%, so some form of self-selection still remains a logical possibility, but we think this is made extremely improbable when there is no decline in the OA Advantage even when mandates quadruple the OA rate from the spontaneous self-selective baseline of 15% to the current mandated average of 60%."
Schneider, J. W., Jan 8, 2010: "the claim of causality seems well beyond the mark. Neither former research nor the current regression design permits any casual claims."
Harnad, S., Jan 9, 2010: "CAUSALITY: We agree that causality is difficult to demonstrate with correlational statistics. However, we note that the hypothesis that (2a) making articles open access causes them to be more citeable and the hypothesis that (2b) being more citeable causes articles to be made open access are both causal hypotheses."
Harnad, S., Open Access: Self-Selected, Mandated & Random; Answers & Questions, Open Access Archivangelism, February 8, 2010: "What follows is what we hope will be found to be a conscientious and attentive series of responses to questions raised by Phil Davis about our paper (currently under refereeing) -- responses for which we did further analyses of our data (not included in the draft under refereeing)."

Added 6 September 2010 Zawacki-Richter, O., Anderson, T. and Tuncay, N. (2010)
The Growing Impact of Open Access Distance Education Journals: A Bibliometric Analysis
The Journal of Distance Education / Revue de l'Éducation à Distance, 24 (3), 2010
From the Abstract: we examine 12 distance education journals (6 open and 6 published in closed format by commercial publishers). Using an online survey completed by members of the editorial boards of these 12 journals and a systematic review of the number of citations per article (N = 1,123) and per journal issue between 2003 and 2008, we examine the impact, and perceived value of the 12 journals. We then compute differences between open and closed journals. The results reveal that the open access journals are not perceived by distance eductation editors as significantly more or less prestigious than their closed counterparts. The number of citations per journal and per article also indicates little difference. However we note a trend towards more citations per article in open access journals. Articles in open access journals are cited earlier than in non-open access journals.

Added 6 September 2010 Kim, J. (2010)
Faculty self-archiving: Motivations and barriers
Journal of the American Society for Information Science and Technology, 16 Jul 2010
info:doi/10.1002/asi.21336
This paper is broader than open access impact, but one part of the investigation looked at it.
From the Discussion: A few interviewees did believe that self-archiving resulted in their research work being cited more frequently, although 13 interviewees were unsure about the positive relationship between self-archiving and the citation rate. Professors even considered self-archiving to serve other purposes, for example, to recruit graduate students, or to find collaborators, instead of increasing the impact of research. In fact, five interviewees expressed uncertainty regarding whether self-archiving would improve professional recognition. Four other interviewees did not expect self-archiving to increase academic recognition, as they believed this related more to the quality of research itself, rather than merely making it publicly accessible. These findings suggested that the majority of faculty participants in this study were unaware of the evidence of a citation advantage from OA previously identified by several studies. Without noticing the evidence, professors tend not to expect a citation advantage from self-archiving; however, they see benefits from the user side through self-archiving. This study shows that faculty have diverse opinions about citation rates and academic recognition related to self-archiving.

Added 6 September 2010 Strotmann, A. and Zhao, D. (2010)
Impact of Open Access on stem cell research: An author co-citation analysis
76th IFLA General Conference and Assembly, Gothenburg, Sweden, 22 Jun 2010
Abstract: We explore the impact of Open Access (OA) on stem cell research through a comparison of research reported in OA and in non-OA publications. Using an author co-citation analysis method, we find that (a) OA and non-OA publications cover similar major research areas in the stem cell field, but (b) a more diverse range of basic and medical research is reported in OA publications, while (c) biomedical technology areas appear biased towards non-OA publications. From the Introduction: many studies have investigated whether OA publication of research results has a positive effect on the citation ranking of those publications ... we approach the comparison between OA and non-OA publishing of research results from a somewhat different perspective. We explore whether there are substantial differences between the intellectual structure of a research field when viewed from either the point of view of the OA publications in that field or from that of its non-OA publications.

Added 6 September 2010 Jacques, T. S. and Sebire, N. J. (2010)
The impact of article titles on citation hits: an analysis of general and specialist medical journals
JRSM Short Reports, 1 (1), 2, 01 Jun 2010
info:doi/10.1258/shorts.2009.100020
More factors to consider in citation impact assessment.
From the Abstract: We hypothesized that specific features of journal titles may be related to citation rates. We reviewed the title characteristics of the 25 most cited articles and the 25 least cited articles published in 2005 in general and specialist medical journals including the Lancet, BMJ and Journal of Clinical Pathology. The title length and construction were correlated to the number of times the papers have been cited to May 2009. Results The number of citations was positively correlated with the length of the title, the presence of a colon in the title and the presence of an acronym. Factors that predicted poor citation included reference to a specific country in the title. Conclusions These data suggest that the construction of an article title has a significant impact on frequently the paper is cited. We hypothesize that this may be related to the way electronic searches of the literature are undertaken.

Added 9 June 2010 Herb, U. (2010)
Alternative Impact Measures for Open Access Documents? An examination how to generate interoperable usage information from distributed open access services
76th IFLA General Conference and Assembly, Gothenburg, Sweden, August 2010, paper available online 29 May 2010
From the Abstract: This contribution shows that most common methods to assess the impact of scientific publications often discriminate open access publications and by that reduce the attractiveness of Open Access for scientists. Assuming that the motivation to use open access publishing services (e.g. a journal or a repository) would increase if these services would convey some sort of reputation or impact to the scientists, alternative models of impact are discussed. Prevailing research results indicate that alternative metrics based on usage information of electronic documents are suitable to complement or to relativize citation based indicators.

Added 9 June 2010 Giglia, E. (2010)
The Impact Factor of Open Access journals: data and trends
DHANKEN, digital repository of HANKEN research, 27 May 2010. In 14th International Conference on Electronic Publishing, Helsinki, 16-18 June 2010. Slides in E-LIS, 21 June 2010 http://eprints.rclis.org/18669/
From the Abstract: The aim of this preliminary work, focused on Gold Open Access, is to test the performance of Open Access journals with the most traditional bibliometric indicator Impact Factor, to verify the hypothesis that unrestricted access might turn into more citations and therefore also good Impact Factor indices. Open Access journals are relatively new actors in the publishing market, and gaining reputation and visibility is a complex challenge. Some of them show impressive Impact Factor trends since their first year of tracking.

Added 17 May 2010 Calver, M. C. and Bradley, J. S. (2010)
Patterns of Citations of Open Access and Non-Open Access Conservation Biology Journal Papers and Book Chapters
Conservation Biology, published online: 23 Apr 2010
From the abstract: We compared the number of citations of OA and non-OA papers in six journals and four books published since 2000 to test whether OA increases number of citations overall and increases citations made by authors in developing countries. After controlling for type of paper (e.g., review or research paper), length of paper, authors' citation profiles, number of authors per paper, and whether the author or the publisher released the paper in OA, OA had no statistically significant influence on the overall number of citations per journal paper. Journal papers were cited more frequently if the authors had published highly cited papers previously, were members of large teams of authors, or published relatively long papers, but papers were not cited more frequently if they were published in an OA source. Nevertheless, author-archived OA book chapters accrued up to eight times more citations than chapters in the same book that were not available through OA, perhaps because there is no online abstracting service for book chapters. There was also little evidence that journal papers or book chapters published in OA received more citations from authors in developing countries relative to those journal papers or book chapters not published in OA. For scholarly publications in conservation biology, only book chapters had an OA citation advantage, and OA did not increase the number of citations papers or chapters received from authors in developing countries.

Added 4 March 2013 Pienta, Amy M., Alter, George C., Lyle, Jared A. (2010)
The Enduring Value of Social Science Research: The Use and Reuse of Primary Research Data
Deep Blue, University of Michigan, 22 Nov 2010. In The Organisation, Economics and Policy of Scientific Research workshop, Torino, April 2010 http://www.carloalberto.org/files/brick_dime_strike_workshopagenda_april2010.pdf
Abstract: The goal of this paper is to examine the extent to which social science research data are shared and assess whether data sharing affects research productivity tied to the research data themselves. We construct a database from administrative records containing information about thousands of social science studies that have been conducted over the last 40 years. Included in the database are descriptions of social science data collections funded by the National Science Foundation and the National Institutes of Health. A survey of the principal investigators of a subset of these social science awards was also conducted. We report that very few social science data collections are preserved and disseminated by an archive or institutional repository. Informal sharing of data in the social sciences is much more common. The main analysis examines publication metrics that can be tied to the research data collected with NSF and NIH funding - total publications, primary publications (including PI), and secondary publications (non-research team). Multivariate models of count of publications suggest that data sharing, especially sharing data through an archive, leads to many more times the publications than not sharing data. This finding is robust even when the models are adjusted for PI characteristics, grant award features, and institutional characteristics.

Added 6 September 2010 Habibzadeh, F. and Yadollahie, M. (2010)
Are Shorter Article Titles More Attractive for Citations? Cross-sectional Study of 22 Scientific Journals
Croatian Medical Journal, 51 (2), April 2010
Open access is not the only factor affecting citation impact. Here is another factor that has received rather less attention. From the Abstract: Longer titles seem to be associated with higher citation rates. This association is more pronounced for journals with high impact factors. Editors who insist on brief and concise titles should perhaps update the guidelines for authors of their journals and have more flexibility regarding the length of the title.

Added 17 May 2010 Agerbæk, A. and Nielsen, K. (2010)
Factors in Open Access which Influence the Impact Cycle
ScieCom info, Vol 6, No 1, 2010 (issue notice posted 22 March 2010)
Short paper illustrating journal publishing flowcharts for non-open access (OA), gold OA and green OA, showing why, in principle, open access might lead to higher citations due to wider and earlier dissemination.

Added 17 May 2010 Wagner, A. B. (2010)
Open Access Citation Advantage: An Annotated Bibliography
Issues in Science and Technology Librarianship, No. 60, Winter 2010 (issue notice posted 16 March 2010)
The bibliography is divided into three sections:
- Review articles [5 reviews]
- Studies showing an open access citation advantage (OACA) [39 articles]
- Studies showing either no OACA effect or ascribing OACA to factors unrelated to OA publication [7 articles]
The following databases were searched ... results were cross-checked against an extensive, more general bibliography (this bibliography). It is interesting to note that no study has ever claimed that OA articles were cited less than TA articles. The research question still being debated is whether other factors explain the widely observed OACA (Open Access Citation Advantage) rather than the mere fact an article is open access.

Added 09 Mar 2010 Snijder, R. (2010)
The profits of free books - an experiment to measure the impact of Open Access publishing
Google sites, undated, but first spotted in the wild 23 February 2010. In Learned Publishing, Vol. 23, No. 4, October 2010, 293-301
Abstract: to measure the impact of Open Access (OA) publishing of academic books, an experiment was set up. During a period of nine months three sets of books were disseminated through an institutional repository, the Google Book Search program or both channels. A fourth set was used as control group. Open Access publishing enhances discovery and online consultation. No relation could be found between OA publishing and citation rates. Contrary to expectations, OA publishing does not stimulate or diminish sales figure. The Google Book Search program is superior compared to the repository.

Added 09 Mar 2010 Swan, A. (2010)
The Open Access citation advantage: Studies and results to date
ECS EPrints, 17 Feb 2010
Abstract: presents a summary of reported studies on the Open Access citation advantage. There is a brief introduction to the main issues involved in carrying out such studies, both methodological and interpretive. The study listing provides some details of the coverage, methodological approach and main conclusions of each study.

Comment on this paper:
Ed., 11 March 2010: expertly moderated review with a telling tabulation of results.
Davis, P., Rewriting the History of the Open Access Debate, the scholarly kitchen blog, Mar 11, 2010: Swan's summary is quite useful for those looking for a distillation of the research literature. What is troubling with this document, however, is the narrative, and it is here that Swan creates a historical revision of the open access debate. In her report, Swan provides a score sheet for the open access game:

Studies finding a positive open access citation advantage = 27
Studies finding no open access citation advantage (or an OA citation disadvantage) = 4

Meta-analysis is set of powerful statistical techniques for analyzing the literature. Its main function is to increase the statistical power of observation by combining separate empirical studies into one über-analysis. Its assumed, however, that the studies are comparable. This is not the case with the empirical literature on open access and citations. Conducting a meta-analysis on this disparate collection of studies is like taking a Veg-O-Matic to a seven-course dinner. Not only does it homogenize the context (and limitations) of each study into a brown and unseemly mess, but it assumes that homogenization of disparate studies somehow results in a clearer picture of scientific truth.
Responses to this blog:
Swan, A., 11 Mar 2010: I am rather surprised that you feel entitled to challenge the development of my own expectations. Surely I am allowed to write about them as a matter of fact, since I had them? So, no rewriting of history there. Intelligent people dont need to be told what they should think about these things, or pointed to particular studies as the only ones that should matter. They can read all of the studies and reach their own conclusions, including about which ones have been carried out in the best way. The score sheet was the only sensible way of summarising the pages-long table. People often ask me how the studies tally up, so tally them up I did.
Wilson, T., 11 Mar 2010: Philip is right, the studies are so different and so many intervening variables have not been taken into consideration, that to conclude that OA leads to increased citation is simply, in the Scottish court judgement, not proven. Coming to a personal opinion on an issue is not the same as demonstrating, scientifically, the probable truth of a hypothesis.
Jim, Mar 11, 2010: In the the hierarchy of evidence a systematic review containing one or more well designed RCTs (randomized controlled trials) is classed as the highest form of evidence. Currently we appear to have one RCT which didnt find a positive OA citation effect, and then a variety of other studies, some better designed than others, some which found an OA effect, and some which didnt. Talk of a meta-analysis is, in my opinion, premature, and until then Id have to back the RCT.
Glass, G. V., Mar 12, 2010: having dedicated 35 years of my efforts to meta analysis and 20 to OA, I cant resist a couple of quick observations. Holding up one set of methods (be they RCT or whatever) as the gold standard is inconsistent with decades of empirical work in meta analysis that shows that perfect studies and less than perfect studies seldom show important differences in results. If the question at hand concerns experimental intervention, then random assignment to groups may well be inferior as a matching technique to even an ex post facto matching of groups. Randomization is not the royal road to equivalence of groups; its the road to probability statements about differences. Claims about the superiority of certain methods are empirical claims. They are not a priori dicta about what evidence can and can not be looked at.
Wilson, D., Update on Meta-Analysis of Studies on Open Access Impact Advantage, Open Access Archivangelism blog, March 17. 2010: "Meta-analysis could be put to good use in this area. It won't resolve the issue of whether the studies that Davis thinks are flawed are in fact flawed. It could explore the consistency in effect across these studies and whether the effect varies by the method used. Both would add to the debate on this issue."
Hooker, B., advantage, schmantage, Open Reading Frame blog, 18 April 2010: "The FUD merchants want to claim that, if no citation advantage exists, there is no point to Open Access: that unless OA papers are currently garnering more citations than their TA equivalents, current levels of access must be adequate; or that if OA papers, which presumably are read more, are not cited more, then OA must be a repository for the second rate. Hence the controversy: it's an easy way to obscure the debate, sending up a cloud of statistical argument like a fleeing cuttlefish squirting ink."

Added 17 Feb 2010 Giglia, E. (2010)
Più citazioni in Open Access? Panorama della letteratura con uno studio sull'Impact Factor delle riviste Open Access
E-LIS, 21 Jan 2010, also in CIBER 1999-2009, 2009 (Ledizioni), pp. 125-145
From the English abstract: This work aims to frame the international debate on the advantage citation of articles published in Open Access, then present and discuss the overall data sull'Impact Factor of open access journals, the result of an original study conducted in the Journal Citation Reports (Thomson Reuters). The basic idea is to test the performance of OA journals according to the traditional bibliometric indicators dell'Impact Factor, in order to test the hypothesis that unrestricted access may involve a greater number of citations and, therefore, also a good impact factor. The results seem to confirm: the 38,62% of Open Access journals included in the "Journal Citation Reports" is positioned in the first five percentile as an indicator when considering the Impact Factor. If you use the Immediacy Index is the percentage is 37.16%, while the second new indicator dell'Impact Factor over 5 years - however, only applies to 356 titles on 479 - the percentage rises to 40.05%.

Added 17 Feb 2010 Davis, P. (2009)
Studies on access: a review
arXiv:0912.3953v1 [cs.DL], 20 Dec 2009
Brief abstract: A review of the empirical literature on access to scholarly information. This review focuses on surveys of authors, article download and citation analysis.

Added 17 Feb 2010 Ibanez, A., Larranaga, P. and Bielza, C. (2009)
Predicting citation count of Bioinformatics papers within four years of publication
Bioinformatics, 25 (24), 3303-3309, 15 December 2009
info:pmid/19819886 | info:doi/10.1093/bioinformatics/btp585
From the abstract: "The possibility of a journal having a tool capable of predicting the citation count of an article within the first few years after publication would pave the way for new assessment systems. Results: This article presents a new approach based on building several prediction models for the Bioinformatics journal. These models predict the citation count of an article within 4 years after publication (global models). To build these models, tokens found in the abstracts of Bioinformatics papers have been used as predictive features, along with other features like the journal sections and 2-week post-publication periods." Comment: Bioinformatics is not an open access journal, so these results are not based on data for open access papers, but they may have parallels with methods for predicting citations and impact based on usage of OA papers (e.g. Brody et al., 2005). Data on which the results are based can be found at the authors' site. Without access to the full paper it is not clear what predictive features are being applied to achieve the claimed successful results: "In these new models, the average success rate for predictions using the naive Bayes and logistic regression supervised classification methods was 89.4% and 91.5%, respectively, within the nine sections and for 4-year time horizon."

Added 10 Dec 2009 Rand, D. G. and Pfeiffer, T. (2009)
Systematic Differences in Impact across Publication Tracks at PNAS
PLoS ONE, 4(12): e8092, December 1, 2009
Investigates citation counts for the three different publication tracks of the Proceedings of the National Academy of Sciences (PNAS). Open access is used as a control factor in the analysis; "To empirically investigate the impact of papers published via each track, we inspect 2695 papers published between June 1, 2004 and April 26, 2005, covering PNAS Volume 101 Issue 22 through Volume 102 Issue 17. For each paper, we examine Thomson Reuters Web of Science citation data as of October 2006 and May 2009, as well as page-view counts as of October 2006. We also note the track through which each paper was published, the topic classification of each paper, the date of publication, and whether each article was published as open access and/or as part of a special feature." In quantifying the size of the OA effect to control, the paper found that "similar to previous observations, Open Access papers receive approximately 25% more citations than non-Open Access papers (Median 2006 [2009] citations: Open access = 12.5 [38], non-Open access = 10 [30]; 75% percentile 2006 [2009] citations: Open access = 21 [61], non-Open access = 17 [50])."

Added 10 Dec 2009 Soong, S. (2009)
Measuring Citation Advantages of Open Accessibility
D-Lib Magazine, 15 (11/12), December 2009
Short study of a small collection of papers deposited after publication in the institutional repository of the Hong Kong University of Science and Technology (HKUST). "A total of 50 archived journal articles that already have 10 or more citation counts in Scopus were randomly selected for inclusion in this study." Claims to present an "easy-to-follow framework for citation impact analysis of open accessibility. This framework allows for direct measurement and comparison of citation rates before and after journal articles are made openly available." The method compares the citation performance of the same article over time pre- and post-open access rather than, as other studies of OA impact, comparing open access papers with non-open access papers from the same source.

Added 10 Dec 2009 Poor, N. (2009)
Global Citation Patterns of Open Access Communication Studies Journals: Pushing Beyond the Social Science Citation Index
International Journal of Communication, Vol. 3, 2009
From the abstract: Connectivity and citations, as used by a large number of scholars in different fields, are a common measure of the health of a discipline. This paper shows the citation patterns for a multinational sample of open access journals in Communication Studies. Their citations are similar to those of the main communication journals, but with more international citations. Differences in the citation patterns are attributable to the international nature of the sampled journals, not to their open access status. From the conclusion: The citation pattern of these open access journals is the same as that for non-open access journals, which is how it should be if open access journals are going to be of the same quality as more established, non-open access journals (recall that open access does require peer-review). The journals in the sample are not in a separate citation space, and they take part in the larger conversation of the field. As such, this indicates, to a certain extent, the health of these journals (they are not isolates in the citing direction), which, in turn, is a decent indicator for the health of the field.

Added 17 Feb 2010 Akre, O., Barone-Adesi, F., Pettersson, A., Pearce, N., Merletti, F., and Richiardi, L. (2009)
Differences in citation rates by country of origin for papers published in top-ranked medical journals: do they reflect inequalities in access to publication?
Journal of Epidemiology and Community Health, 24 Nov 2009
info:pmid/19934169 | info:doi/10.1136/jech.2009.088690
Investigates the connection between citations and access, but not open access, by country and income with reference to the country of publication. From the abstract: "Methods: We obtained the number of citations and the corresponding authors country for 4724 papers published between 1998 and 2002 in the British Medical Journal, the Lancet, Journal of the American Medical Association, New England Medical Journal. Countries were grouped according to the World Bank classification and geographic location: low-middle income countries, European high-income countries, non-European high-income countries, UK and USA. Conclusions: Papers from different countries published in the same journal have different citation rates."

Added 10 Dec 2009 Mertens, S. (2009)
Open Access: Unlimited Web Based Literature Searching
Dtsch Arztebl Int., 106(43): October 23, 2009, 710-712
Reviews the findings of most of the principal papers found in this bibliography

Added 15 July 2009 Kousha, K. and Abdoli, M. (2009)
The citation impact of Open Access Agricultural Research: a comparison between OA and Non-OA publications (pdf 12pp)
World Library And Information Congress: 75th IFLA General Conference and Council, 23-27 August 2009, Milan, Italy. Also in Online Information Review, Vol. 34, No. 5, 2010, 772-785 http://dx.doi.org/10.1108/14684521011084618
Blogged summary, Open Access enhances accessibility and citation impact, International Association of Agricultural Information Specialists, 13 July 2009: "The results showed that there is an obvious citation advantage for self-archived agriculture articles as compared to non-OA articles." - "results indicate that self-archived research articles published in the non-OA agriculture journals could attract nearly two times more citations than their non-OA counterparts."

Added 15 Oct 2009 Lariviere, V. and Gingras, Y. (2009)
The impact factor's Matthew effect: a natural experiment in bibliometrics
arXiv.org, arXiv:0908.3177v1 [physics.soc-ph], 21 Aug 2009, also in Journal of the American Society For Information Science And Technology, 61 (2): 424-427, February 2010
Makes no mention of open access impact, but presents some interesting parallel results on journal impact factors, in this case that publication in higher impact journals can result in higher citations for a given paper.

Added 15 Oct 2009 Asif-ul Haque and Ginsparg, P. (2009)
Positional Effects on Citation and Readership in arXiv
arXiv.org, arXiv:0907.4740v1 [cs.DL], 27 Jul 2009
in Journal of the American Society for Information Science and Technology, Vol. 60 No. 11, 2203 - 2218, published online: 22 Jul 2009

Added 15 Oct 2009 Greyson, D., Morgan, S., Hanley, G. and Wahyuni, D. (2009)
Open access archiving and article citations within health services and policy research
E-LIS, 14 Jul 2009, in Journal of the Canadian Health Libraries Association (JCHLA) / Journal de l'Association des bibliothèques de la santé du Canada (JABSC), 2009, vol. 30, no. 2, 51-58
From the abstract: This paper contributes to growing body of research exploring the “OA advantage” by employing an article-level analysis comparing citation rates for articles drawn from the same, purposively selected journals. We used a two-stage analytic approach designed to test whether OA is associated with (1) likelihood that an article is cited at all and (2) total number citations that an article receives, conditional on being cited at least once. Adjusting for potential confounders: number of authors, time since publication, journal, and article subject, we found that OA archived articles were 60% more likely to be cited at least once, and, once cited, were cited 29% more than non-OA articles.This paper contributes to growing body of research exploring the “OA advantage” by employing an article-level analysis comparing citation rates for articles drawn from the same, purposively selected journals. We used a two-stage analytic approach designed to test whether OA is associated with (1) likelihood that an article is cited at all and (2) total number citations that an article receives, conditional on being cited at least once. Adjusting for potential confounders: number of authors, time since publication, journal, and article subject, we found that OA archived articles were 60% more likely to be cited at least once, and, once cited, were cited 29% more than non-OA articles.
See also this poster (1pp) with the same title, E-LIS, 14 Jul 2009, in Canadian Health Libraries Association/ Association des bibliothèques de la santé du Canada (CHLA/ ABSC) Conference 2009, Winnepeg, Manitoba (Canada), May 30 - June 3, 2009

Added 15 Oct 2009 Joint, N. (2009)
The Antaeus column: does the “open access” advantage exist? A librarian's perspective
Library Review, Vol. 58, No. 7, 2009, 477-481
From the summary: Findings – The paper finds that many of the original arguments for the benefits of open access have fallen by the wayside; but that, in spite of this, there is a good evidence that an “open access advantage” does exist. The application of straightforward library statistical counting measures which are traditionally used to evaluate user benefits of mainstream services is just as effective an evaluation tool as more sophisticated citation analysis methods.

Added 15 July 2009 Gentil-Beccot, A., Mele, S., Brooks, T. (2009)
Citing and Reading Behaviours in High-Energy Physics. How a Community Stopped Worrying about Journals and Learned to Love Repositories
arXiv.org, arXiv:0906.5418v1 [cs.DL], v1, 30 Jun 2009
From the abstract: The analysis of citation data demonstrates that free and immediate online dissemination of preprints creates an immense citation advantage in HEP, whereas publication in Open Access journals presents no discernible advantage. In addition, the analysis of clickstreams in the leading digital library of the field shows that HEP scientists seldom read journals, preferring preprints instead.

Added 15 July 2009 Lansingh, V. C. and Carter, M. J. (2009)
Does Open Access in Ophthalmology Affect How Articles are Subsequently Cited in Research? (abstract only, subscription required)
Ophthalmology, 116(8):1425-1431, August 2009, available online 22 June 2009
From the abstract: Examination of 480 articles in ophthalmology in the experimental protocol and 415 articles in the control protocol. ... Four subject areas were chosen to search the ophthalmology literature in the PubMed database ... Searching started in December of 2003 and worked back in time to the beginning of the year. The number of subsequent citations for equal numbers of both open access (OA) and closed access (CA) (by subscription) articles was quantified using the Scopus database and Google search engine. A control protocol was also carried out to ascertain that the sampling method was not systematically biased by matching 6 ophthalmology journals (3 OA, 3 CA) using their impact factors, and employing the same search methodology to sample OA and CA articles. The total number of citations was significantly higher for open access articles compared to closed access articles for Scopus. However, univariate general linear model (GLM) analysis showed that access was not a significant factor that explained the citation data. Author number, country/region of publication, subject area, language, and funding were the variables that had the most effect and were statistically significant. Control protocol results showed no significant difference between open and closed access articles in regard to number of citations found by Scopus ... Unlike other fields of science, open access thus far has not affected how ophthalmology articles are cited in the literature.

Added 29 April 2009 Tiwari, A. (2009)
Citation Trend Line For PLoS Journals
Fisheye Perspective blog, April 25, 2009
A short illustrated blog on predicting the impact of a new journal. The author, a bioscientist, evaluates two PLoS (OA) journals using Scopus Journal Analyzer. Using the service's Trend Line and % Not Cited parameters the author predicts that one, a new journal that doesn't yet have an official impact factor, will soon rival the other, which does: "I am sure it's impact factor (or quality or what ever you love) is going to be same or may be much more." Does not claim to be statistically sound.

Added 29 April 2009 Gargouri, Y. and Harnad, S. (2009)
Logistic regression of potential explanatory variables on citation counts
Preprint 11/04/2009
Logistic regression analysis on the correlation between citation counts (as dependent variable) and a set of potential correlator/predictor variables.
Result: Published journal papers that are self-archived in institutional repositories - in this study the repositories mandate deposit, obviating the self-selection bias postulated by some to be a factor in self-archiving - can achieve a citation advantage whether published in journals of high and low impact factor (IF): "Overall, OA is correlated with a significant citation advantage for all journal IF intervals".

Added 29 April 2009 Watson, A. B. (2009)
Comparing citations and downloads for individual articles
Journal of Vision, April 3, 2009 Volume 9, Number 4, Editorial i, Pages 1-4
Measures the correlation between downloads and citations counts for articles in Journal of Vision: "Download statistics provide a useful indicator, two years in advance, of eventual citations."

Added 29 April 2009 Bollen, J., Van de Sompel, H., Hagberg, A., Bettencourt, L., Chute, R., Rodriguez, M. A. and Balakireva, L. (2009)
Clickstream Data Yields High-Resolution Maps of Science
PLoS ONE, 4(3): e4803, March 11, 2009
See also Nature news article on this paper, 9 March 2009: "A striking difference in the usage maps is that journals in the humanities and social sciences figure much more prominently than in citation-based maps. The difference partly arises because Bollen's study covers a wider literature than the citation databases, which are biased towards natural sciences journals. "By including practitioners we capture a much wider sample of the scholarly community," adds Bollen. Usage maps are also more up to date than citation ones because the inherent delay in publication means it takes at least two years before a paper will start to gather citations in sufficient numbers to be meaningful. Anthony van Raan argues that this more current view may in fact represent today's "fashions", rather than trends that will endure."
These findings are not based on OA journals or papers, but highlight the emerging value of clicks, or hits, as possible contributory factors for online impact metrics.

Added 29 April 2009 Åström, F. (2009)
Citation patterns in open access journals
OpenAccess.se and the National Library of Sweden, February 25, 2009.
"Fewer analyses have investigated whether OA and non-OA journals in the same research fields are citing the same literature; and to what extent this reflects whether it is the same kind (and thus comparable) research that is published in the two forms of scholarly publications. ... The citation structures in the journals were analysed through MDS maps building on co-citation analyses, as well as a more thorough comparison investigating overlaps of cited authors and journals between the different journals. ... The results of the analyses suggests that it is hard to draw any overall conclusions on the matter of whether research published in OA journals is likely to have a larger citation impact or not."
This conclusion is unsurprising since the study did not measure impact but mapped citation patterns between journals. It is suggested that these mappings could improve understanding when comparing the impact of OA and non-OA journals.

Added 29 April 2009 Gaulé, P. (2009)
Access to the scientific literature in India
CEMI Working Paper 2009-004, February 23, 2009, in In Journal of the American Society for Information Science and Technology, Vol. 60, Issue 12, 2548 - 2553, published online: 8 Oct 2009
Abstract: This paper uses an evidence-based approach to assess the difficulties faced by developing country scientists in accessing the scientific literature. I compare backward citations patterns of Swiss and Indian scientists in a database of 43'150 scientific papers published by scientists from either country in 2007. Controlling for fields and quality with citing journal fixed effects, I find that Indian scientists (1) have shorter references lists (2) are more likely to cite articles from open access journals and (3) are less likely to cite articles from expensive journals. The magnitude of the effects is small which can be explained by informal file sharing practices among scientists.
See also
Patrick Gaulé and Nicolas Maystre, Free availability and diffusion of scientific articles, Vox, 23 June 2009

Added 26 February 2009 Evans, J. A. and Reimer, J. (2009)
Open Access and Global Participation in Science (full text requires subscription; summary only)
Science, Vol. 323. No. 5917, 20 February 2009, 1025
From the paper: "The influence of OA is more modest than many have proposed, at c.8% for recently published research, but our work provides clear support for its ability to widen the global circle of those who can participate in science and benefit from it."
Listen to Science podcast interview with James Evans
See also articles on this paper:
Dolgin, E., Online access = more citations, The Scientist, 19th February 2009 (free registration required): "When the authors looked just at poorer countries, however, they found that the influence of open access was more than twice as strong. For example, in Bulgaria and Chile, researchers cited nearly 20% more open access articles, and in Turkey and Brazil, the number of citations rose by more than 25%. Free online availability "is not a huge driver of science in the first world, but it shapes parts of science in the rest of world," Evans told The Scientist."
Xie, Y., Open, electronic access to research crucial for global reach, ars technica, February 19, 2009

Comment on this paper:
Harnad, S., Open Access Benefits for the Developed and Developing World: The Harvards and the Have-Nots, Open Access Archivangelism blog, Feb 19, 2009: "Evans & Reimer's study (E & R) is particularly timely and useful. It shows that a large portion of the Open Access citation impact advantage comes from providing the developing world with access to the research produced by the developed world. Using a much bigger database, E & R refute (without citing!) a recent flawed study (Frandsen 2009) that reported that there was no such effect ... Last, there is the question of the effect of access embargoes. It is important to note that E & R's results are not based on immediate OA but on free access after an embargo of up to a year or more. Theirs is hence not an estimate of the increase in citation impact that results from immediate Open Access; it is just the increase that results from ending Embargoed Access."
See also this blog on the 'silly spin' of the NSF press release on the paper and on the 'welter of misunderstandings' of a follow-up blog based on the press release in the Chronicle of Higher Education.
Davis, P., Open Access and Global Participation in Science, the scholarly kitchen blog, Feb 19, 2009: "Advocates for open access will see this article as supporting their cause. But those who spend time reading the methodology will notice that message is not as clear as the article implies."
Eisen, M., Letter to the editor in Science, it is NOT junk blog, July 17, 2009: "the 8% statistic that Evans and Reimer highlight is misleading. The authors supporting online material (figure S1C) clearly shows that the impact of free access on citations is heavily dependent on the age of the article at the time free access was provided. In particular, when articles were made freely available within 2 years of publication, their citations increased by almost 20%. This far more dramatic effect is the one scientists and journals should consider when deciding when to provide free access. If this decision is to be made purely on the basis of citation impact, the upward trend of the curve in figure S1C argues strongly in favor of minimal delays."
Four Letters on this paper are published in the Science issue of 17 July 2009, Vol 325, issue 5938, including this one by Eisen (and Salzberg), as well as others by Davis ('Increased Citations Not Guaranteed'), Burdett ('The Self-Selection Effect'), and Alberts ('The Sooner the Better'), with a repsonse by the original authors.

Added 26 February 2009 Bollen, J., Van de Sompel, H., Hagberg, A. and Chute, R. (2009)
A principal component analysis of 39 scientific impact measures
arXiv.org, arXiv:0902.2183v1 [cs.CY], 12 Feb. 2009, in PLoS ONE 4(6): e6022, http://dx.doi.org/10.1371/journal.pone.0006022

Added 29 April 2009 Castillo, M. (2009)
Citations and Open Access: Questionable Benefits
American Journal of Neuroradiology, February 2009
An editorial.
(Ed. For the record, but I cannot indicate what is questionable about OA, in this author's view, as I can't access any part of this, not even an abstract.)

Added 26 February 2009 Norris, M. (2009)
The citation advantage of open access articles
PhD thesis, Loughborough University Institutional Repository, 2009-01-15
Michael Norris has been named Highly Commended Award winner of the 2008 Emerald/EFMD Outstanding Doctoral Research Award in the Information Science category for this doctoral thesis.
Two published papers (JASIST, ElPub) are based on this work.

Added 13 January 2009 O'Leary, D. E. (2008)
The relationship between citations and number of downloads
Decision Support Systems, Vol. 45, No. 4, November 2008, 972-980, available online 11 April 2008 (full text requires subscription; abstract only)
Broadly agrees with earlier findings (e.g. Brody et al.) about the correlation - 'strong positive statistically significant relationship' - between downloads and citations for digital papers, notably for the most-downloaded, 'top' papers, in this case based on data for a single, focussed source, the journal Decision Support Systems.

Added 29 April 2009 Mukherjee, B. (2008)
Do open-access journals in library and information science have any scholarly impact? A bibliometric study of selected open-access journals using Google Scholar (full text requires subscription; abstract only)
Journal of the American Society for Information Science and Technology, Vol. 60, No. 3, March 2009, 581-594, published online: 16 Dec 2008
From the abstract: "Using 17 fully open-access journals published uninterruptedly during 2000 to 2004 in the field of library and information science, the present study investigates the impact of these open-access journals in terms of quantity of articles published, subject distribution of the articles, synchronous and diachronous impact factor, immediacy index, and journals' and authors' self-citation."
The paper does not appear to reveal any comparative findings (OA vs non-OA).

Added 24 November 2008 Tenopir, C. and King, D. W. (2008)
Electronic Journals and Changes in Scholarly Article Seeking and Reading Patterns
D-Lib Magazine, Vol. 14 No. 11/12, November/December 2008
From the abstract: "Reading patterns and citation patterns differ, as faculty read many more articles than they ultimately cite and read for many purposes in addition to research and writing. The number of articles read has steadily increased over the last three decades, so the actual numbers of articles found by browsing has not decreased much, even though the percentage of readings found by searching has increased. Readings from library-provided electronic journals has increased substantially, while readings of older articles have recently increased somewhat. Ironically, reading patterns have broadened with electronic journals at the same time citing patterns have narrowed."

Added 24 November 2008 Gaule, P. and Maystre, N. (2008)
Getting cited: does open access help?
Ecole Polytechnique Fédérale de Lausanne, CEMI-WORKINGPAPER-2008-007, November 2008. In Research Policy, in press, available online 2 July 2011 info:doi/10.1016/j.respol.2011.05.025. Also available from RePEc http://ideas.repec.org/p/cmi/wpaper/cemi-workingpaper-2008-007.html
Explains the 'widely held belief' that free availability of scientific articles increases the number of citations they receive thus: "Since open access is relatively more attractive to authors of higher quality papers, regressing citations on open access and other controls yields upward-biased estimates." Findings are based on a sample of 4388 biology papers published between May 2004 and March 2006 by Proceedings of the National Academy of Sciences (PNAS). "Using an instrumental variable approach, we find no significant effect of open access. Instead, self-selection of higher quality articles into open access explains at least part of the observed open access citation advantage." Note, OA in PNAS is itself self-selective by virtue of its OA charging structure (i.e. payment is required for the published article to be OA, but not if it is not OA).
See also
Patrick Gaulé and Nicolas Maystre, Free availability and diffusion of scientific articles, Vox, 23 June 2009

Comment on this paper:

Comments below refer to the Research Policy publication
Added 25 November 2011 Harnad, S., Getting Excited About Getting Cited: No Need To Pay For OA, Open Access Evangelism, August 19. 2011: What G & M have shown, convincingly, is that in the special case of having to pay for OA in a hybrid Gold Journal (PNAS: a high-quality journal that makes all articles OA on its website 6 months after publication), the article quality and author self-selection factors alone (plus the availability of funds in the annual funding cycle) account for virtually all the significant variance in the OA citation advantage: Paying extra to provide hybrid Gold OA during those first 6 months does not buy authors significantly more citations. G & M correctly acknowledge, however, that neither their data nor their economic model apply to Green OA self-archiving, which costs the author nothing and can be provided for any article, in any journal (most of which are not made OA on the publisher's website 6 months after publication, as in the case of PNAS). Yet it is on Green OA self-archiving that most of the studies of the OA citation advantage (and the ones with the largest and most cross-disciplinary samples) are based.

Comments below refer to the preprint
Davis, P., Should You Pay To Get Cited?, the scholarly kitchen blog, 18 November 2008: "This study adds to a growing literature that casts doubt on early research suggesting that free access to the scientific literature leads to increased citations. Self-selection, whereby higher quality articles are made freely available, is beginning to seem a much more plausible explanation."

Added 26 February 2009 Frandsen, T. F. (2008)
Attracted to open access journals: a bibliometric author analysis in the field of biology
Hprints, Nordic arts and humanities e-print archive, HAL: hprints-00328270, version 1, 10 October 2008
also in Journal of Documentation, January 2009 http://www.emeraldinsight.com/Insight/viewContentItem.do?contentType=Article&contentId=1766883

Comment on this paper:
Davis, P., Open Access: No Benefit for Poor Scientists, the scholarly kitchen blog, Jan 14, 2009: "Open Access has a moral agenda: to increase the flow of scientific information to researchers in developing nations. Yet a new study suggests that authors in developing countries are no more likely to write papers for Open Access journals and are no more likely to cite Open Access articles." Appended to Davis' blog, Gaule, P., 14 Jan. 2009: "Ms Frandsen's conclusion that 'authors from developing countries do not cite open access more than authors from developed countries' is not based on solid evidence. While she reports the p-value and not the standard errors, it is clear from her regression results that she cannot statistically rule out the possibility that authors from developing countries may be more likely to cite open access journals."
Harnad, S., Comparing OA/non-OA in Developing Countries, Open Access Archivangelism blog, January 14. 2009: "The Frandsen study focused on OA journals, not on OA articles. It is problematic to compare OA and non-OA journals, because journals differ in quality and content, and OA journals tend to be newer and fewer than non-OA journals (and often not at the top of the quality hierarchy). In contrast, most studies that have compared OA and non-OA articles within the same journal and year have found a significant citation advantage for OA. It is highly unlikely that this is only a developed-world effect; indeed it is almost certain that a goodly portion of OA's enhanced access, usage and impact comes from developing-world users."
Chan, L., Comparing OA/non-OA in Developing Countries, Open Access Archivangelism blog, January 14. 2009: "The Frandsen study focuses on biology journals and I am not sure what percentage of them are available to DC researchers through HINARI/AGORA. This would explain why researchers in this area would not need to rely on OA materials as much. Citation behaviour is complex indeed and more studies on OA's impact in the developing world are clearly needed. Davis's eagerness to pronounce that there is "No Benefit for Poor Scientists" based on one study is highly premature."

Added 26 February 2009 Frandsen, T. F. (2008)
The integration of open access journals in the scholarly communication system: Three science fields
Hprints, Nordic arts and humanities e-print archive, HAL: hprints-00326285, version 1, 2 October 2008
also in Information Processing & Management, January 2009 http://dx.doi.org/10.1016/j.ipm.2008.06.001
From the abstract: "This study is an analysis of the citing behaviour in (open access) journals within three science fields: biology, mathematics, and pharmacy and pharmacology. The integration of OAJs in the scholarly communication system varies considerably across fields. The implications for bibliometric research are discussed."

Added 13 January 2009 De Groote, S. L (2008)
Citation patterns of online and print journals in the digital age
J. Med. Libr. Assoc., 2008 October; 96(4): 362-369
From the abstract: "Journals available in electronic format were cited more frequently in publications from the campus whose library had a small print collection, and the citation of journals available in both print and electronic formats generally increased over the years studied."

Added 10 November 2008 Kousha, K. (2008)
Characteristics of Open Access Web Citation Network: A Multidisciplinary Study
Proceedings of WIS 2008, Fourth International Conference on Webometrics, Informetrics and Scientometrics & Ninth COLLNET Meeting (Berlin, 28 July - 1 August 2008), edited by H. Kretschmer and F. Havemann, October 2008

Added 10 November 2008, updated 29 April 2009 Lariviere, V., Gingras, Y. and Archambault, E. (2008)
The decline in the concentration of citations, 1900-2007
arXiv.org, arXiv:0809.5250v1 [physics.soc-ph], 30 Sep 2008 and in Journal of the American Society for Information Science and Technology, Vol. 60, No. 4, April 2009, 858-862, published online: 29 Jan 2009
From the abstract: "This paper challenges recent research (Evans, 2008) reporting that the concentration of cited scientific literature increases with the online availability of articles and journals. ... contrary to what was reported by Evans, the dispersion of citations is actually increasing."

Added 25 September 2008 Davis, P. M.
Author-choice open access publishing in the biological and medical literature: a citation analysis
arXiv.org, arXiv:0808.2428v1 [cs.DL], 18 Aug 2008, in Journal of the American Society for Information Science & Technology, Vol. 60, No. 1, January 2009, 3-8, published online: 25 Sep 2008
This study is a follow-up to the controlled trial of open access publishing published in the BMJ: "According to a study of 11 biological and medical journals that allow authors the choice of making their articles freely available from the publisher's website, few show any evidence of a citation advantage. For those that do, the effect appears to be diminishing over time. ... (the paper) analyzed over eleven thousand articles published in journals since 2003, sixteen hundred of these articles (15%) adopting the author-choice open access model."

Added 25 September 2008 Clauson, K. A., Veronin, M. A., Khanfar, N. M. and Lou, J. Q.
Open-access publishing for pharmacy-focused journals (full text requires subscription; summary only)
American Journal of Health-System Pharmacy, Vol. 65, No. 16, 1539-1544, August 15, 2008
From the conclusion. A very small number of pharmacy-focused journals adhere to the OA paradigm of access. However, journals that adopt some elements of the OA model, chiefly free accessibility, may be more likely to be cited than traditional journals. Pharmacy practitioners, educators, and researchers could benefit from the advantages that OA offers but should understand its financial disadvantages.
The same issue has an editorial by C. Richard Talley, Open-access publishing: why not? accessible only to subscribers

Added 10 November 2008 Henneken, E. A., Kurtz, M. J., Accomazzi, A., Grant, C. S., Thompson, D., Bohlen, E. and Murray, S. S. (2008)
Use of Astronomical Literature - A Report on Usage Patterns
arXiv.org, arXiv:0808.0103v1 [cs.DL], 1 Aug 2008
in Journal of Informetrics, Vol. 3, Issue 1, 1-90 (January 2009)

Comment on this paper:
Godlee, F., Open access to research (editorial), BMJ, 2008;337:a1051, 31 July 2008: "This week the BMJ publishes a paper that has nothing directly to do with medicine or health care. It does, however, have everything to do with access to research results, a topic that should interest authors and readers in any field. ... questions that reach to the very heart of the way in which scientists and clinicians communicate. ... questions also reach to the heart of how academics are acknowledged and rewarded."
Anderson, K. (2008), Open Access Doesn't Drive Citations, The Scholarly Kitchen blog, July 31, 2008: "First, a caveat. Phil Davis is a fellow blogger on this site. This study has important advantages over prior studies. It was randomized by the researchers, so authors or publishers didn't select which articles were made open access. It was done prospectively, so that the data were analyzed from point zero forward. These are crucial advantages in study design, in my opinion, and place this study head and shoulders above any prior study asserting a citation advantage. In fact, authors and editors often make studies they think are more significant free or push them online early. Retrospective, non-randomized studies fall prey to all sorts of problems because of these confounding effects."
Harnad, S. (2008), Davis et al's 1-year Study of Self-Selection Bias: No Self-Archiving Control, No OA Effect, No Conclusion, Open Access Archivangelism blog, July 31, 2008: "To show that the OA advantage is an artefact of self-selection bias (or of any other factor), you first have to produce the OA advantage and then show that it is eliminated by eliminating self-selection bias (or any other artefact). This is not what Davis et al. did. They simply showed that they could detect no OA advantage one year after publication in their sample. This is not surprising, since most other studies, some based on hundreds of thousands of articles, don't detect an OA advantage one year after publication either. It is too early. To draw any conclusions at all from such a 1-year study, the authors would have had to do a control condition, in which they managed to find a sufficient number of self-selected, self-archived OA articles (from the same journals, for the same year) that do show the OA advantage, whereas their randomized OA articles do not. In the absence of that control condition, the finding that no OA advantage is detected in the first year for this particular sample of 247 out of 1619 articles in 11 physiological journals is completely uninformative. The authors did find a download advantage within the first year, as other studies have found. This early download advantage for OA articles has also been found to be correlated with a citation advantage 18 months or more later. The authors try to argue that this correlation would not hold in their case, but they give no evidence (because they hurried to publish their study, originally intended to run four years, three years too early.)"
Eysenbach, G. (2008), Word is still out: Publication was premature, BMJ Rapid Responses, 1 August 2008: "While parts of the paper will be welcomed by most Open Access advocates as far as the access/usage data are concerned, showing (unsurprisingly) a significant increase in access and use of Open Access articles compared to non-OA articles, other parts of the paper are more controversial (to be diplomatic). Davis et al failed to show a citation advantage after 9-12 months, from which they conclude that "the citation advantage from open access reported widely in the literature may be an artifact of other causes." Jumping to these conclusions after only 9-12 months is quite irritating ... What surprised (and bothered) me especially is that Davis et al. cites my PNAS data published in PLoS Biology to justify his short observation period. While I indeed found already a statistically significant difference after only 4-10 months (1.2 citations in the nOA group versus 1.5 citations in the OA group), most citations appeared after 10-16 months (4.5 versus 6.4) and 16-22 months (8.9 vs 13.1). In summary, this would have been an important and much more credible paper if it would have been published in 2-3 years as opposed to a salami approach."
More Rapid Responses to this paper
Harnad, S., On Eggs and Citations, Open Access Archivangelism blog, August 29, 2008: "Failing to observe a platypus laying eggs is not a demonstration that the platypus does not lay eggs. ... Failing to observe a significant OA citation Advantage within a year of publication (or a year and a half -- or longer, as the case may be) with randomized OA does not demonstrate that the many studies that do observe a significant OA citation Advantage with nonrandomized OA are simply reporting self-selection artifacts (i.e., selective provision of OA for the more highly citable articles.) ... The many reports of the nonrandomized OA Citation Advantage are based on samples that were sufficiently large, and on a sufficiently long time-scale (almost never as short as a year) to detect a significant OA Citation Advantage. A failure to observe a significant effect with small, early samples, on short time-scales -- whether randomized or nonrandomized -- is simple that: a failure to observe a significant effect: Keep testing till the size and duration of your sample of randomized and nonrandomized OA is big enough to test your self-selection hypothesis (i.e., comparable with the other studies that have detected the effect)."

Added 24 November 2008 Levitt, J. M. and Thelwall, M. (2008)
Patterns of annual citation of highly cited articles and the prediction of their citation ranking: A comparison across subjects (full text requires subscription; abstract only)
Scientometrics, Vol. 77, No. 1 (2008) 41-46, published online: 24 July 2008
From the abstract: "For four of the six subjects, there is a correlation of over 0.42 between the percentage of early citations and total citation ranking but more highly ranked articles had a lower percentage of early citations. Surprisingly, for highly cited articles in all six subjects the prediction of citation ranking from the sum of citations during their first six years was less accurate than prediction using the sum of the citations for only the fifth and sixth year."
Open access is not a factor here. The highly-cited subject articles investigated here date from 1969-71. For open access papers, Brody et al. (2005) revealed a correlation to predict impact from much earlier data, i.e. download data for OA papers, before any citations.

Added 28 July 2008 Evans, J. A. (2008)
Electronic Publication and the Narrowing of Science and Scholarship (full text requires subscription; abstract only)
Science, Vol. 321, No. 5887, 18 July 2008, 395-399
From the abstract: "Using a database of 34 million articles, their citations (1945 to 2005), and online availability (1998 to 2005), I show that as more journal issues came online, the articles referenced tended to be more recent, fewer journals and articles were cited, and more of those citations were to fewer journals and articles. The forced browsing of print archives may have stretched scientists and scholars to anchor findings deeply into past and present scholarship. Searching online is more efficient and following hyperlinks quickly puts researchers in touch with prevailing opinion, but this may accelerate consensus and narrow the range of findings and ideas built upon."
This work was funded by the National Science Foundation. See the NSF press release and video interview with James Evans
See also the news feature Great minds think (too much) alike, The Economist, July 17th 2008

Comment on this paper:
Davis, P. (2008), The Paradox of Online Journals, The Scholarly Kitchen blog, July 18, 2008: "This does not mean that total citations are dropping, only that fewer articles get cited more. While it is tempting to eulogize the end of scholarship, this article may signify that the dissemination of science is working more efficiently than ever. The institution of science values the progress of discovery followed by a consensus and closure of debate. That more of the literature is effectively being ignored may not necessarily signal a bad thing (although it may concern those who are not read)."
Hooker, Bill (2008), An Open Access partisan's view, Open Reading Frame blog, 19 July 2008: "Evans seems to me to gloss over the question of what proportion of the online archives are freely available, and what effect that has on the phenomenon he is attempting to model. ... the driving force in Evans' suggested "narrow[ing of] the range of findings and ideas built upon" is not online access per se but in fact commercial access, with its attendant question of who can afford to read what. Evans' own data indicate that if the online access in question is free of charge, the apparent narrowing effect is significantly reduced or even reversed."
For collected comments on this paper, see Electronic Publication and the Narrowing of Science and Scholarship. Really? A Blog Around the Clock, July 19, 2008
Suber, P. (2008), Online researchers have access to more articles but cite fewer, Open Access News, July 17, 2008: "Evans' results also appear to conflict with a recent study by Arthur Eger."
Harnad, S. (2008), Are Online and Free Online Access Broadening or Narrowing Research? Open Access Archivangelism blog, August 4, 2008: "In one of the few fields where [the narrowing citations effect found by Evans] can be and has been analyzed thoroughly, astrophysics, which effectively has 100% Open Access (OA) (free online access) already, Michael Kurtz too found that with free online access to everything, reference lists became (a little) shorter, not longer, i.e., people are citing (somewhat) fewer papers, not more, when everything is accessible to them. ... Are online and free online access broadening or narrowing research? They are broadening it by making all of it accessible to all researchers, focusing it on the best rather than merely the accessible, and accelerating it."
Gingras, Y., Lariviere, V. and Archambault, E. (2008), Literature Citations in the Internet Era (Letter), Science, Vol. 323, No. 5910, 2 January 2009, 36: "(Evans's) conclusions are not warranted by (the) data. ... In fact, Evans's conclusions only reflect a transient phenomenon related to recent access to online publications and to the fact that the method used does not take into account time delays between citation year and publication year."

Added 25 September 2008, updated 13 January 2009 Norris, M., Oppenheim, C., and Rowland, F.
The citation advantage of open-access articles (full text requires subscription; abstract only)
Journal of the American Society for Information Science and Technology, Vol. 59, No. 12, 2008, 1963-1972, published online: 9 July 2008
also available from Loughborough University Institutional Repository, 2009-01-12 http://hdl.handle.net/2134/4083
From the abstract: "Of a sample of 4,633 articles examined, 2,280 (49%) were OA and had a mean citation count of 9.04 whereas the mean for (toll access) TA articles was 5.76. There appears to be a clear citation advantage for those articles that are OA as opposed to those that are TA. This advantage, however, varies between disciplines, with sociology having the highest citation advantage, but the lowest number of OA articles, from the sample taken, and ecology having the highest individual citation count for OA articles, but the smallest citation advantage. Tests of correlation or association between OA status and a number of variables were generally found to weak or inconsistent. The cause of this citation advantage has not been determined."

Updated 25 September 2008 Norris, M., Oppenheim, C. and Rowland, F. (2008)
Open Access Citation Rates and Developing Countries
12th International Conference on Electronic Publishing (ElPub 2008), Toronto, June 25-27, 2008
"the admittedly small number of citations from authors in developing countries do indeed seem to show a higher proportion of citations being given to OA articles than is the case for citations from developed countries."

Added 26 May 2008 Cheng, W. H. and Ren, S. L. (2008)
Evolution of open access publishing in Chinese scientific journals (full text requires subscription; abstract only)
Learned Publishing, Vol. 21, No. 2, April 2008, 140-152
From the abstract: "Citation indicators of OA journals were found to be higher than those of non-OA journals."

Added 28 July 2008 Harnad, S., Brody, T., Vallières, F., Carr, L., Hitchcock, S., Gingras, Y., Oppenheim, C., Hajjem, C. and Hilf, E. R. (2008)
The Access/Impact Problem and the Green and Gold Roads to Open Access: An Update
Serials Review, Vol. 34, Issue 1, March 2008, 36-40, available online 6 March 2008
also available from ECS EPrints, 06 Jun 2008 http://eprints.ecs.soton.ac.uk/15852/
Update to the paper published in Serials Review, 30(4), 2004

Added 11 February 2008 Chu, H. and Krichel, T. (2008)
Downloads vs. Citations: Relationships, Contributing Factors and Beyond
E-LIS, 9 February 2008, in 11th Annual Meeting of the International Society for Scientometrics and Informetrics, Madrid, 25-27 June 2007
From the abstract: "In a nutshell, an infrastructure that encourages downloading at digital libraries would eventually lead to higher usage of their resources."

Added 26 May 2008 Turk, N. (2008)
Citation impact of Open Access journals (full text requires subscription; summary only)
New Library World, Vol. 109, No. 1/2, January/February 2008, 65-74
Review of the main research about citation impact of Open Access journals, focused on LIS journals.

Added 26 May 2008 Hardisty, D. J. and Haaga, D. A. F. (2008)
Diffusion of Treatment Research: Does Open Access Matter? (pdf 39pp)
Center for the Decision Sciences, Columbia University, in Journal of Clinical Psychology, Vol. 64(7), 1-19 (2008)
From the abstract: "In a pair of studies, mental health professionals were given either no citation, a normal citation, a linked citation, or a free access citation and were asked to find and read the cited article. After one week, participants read a vignette on the same topic as the article and gave recommendations for an intervention. In both studies, those given the free access citation were more likely to read the article, yet only in one study did free access increase the likelihood of making intervention recommendations consistent with the article."

Added 11 February 2008 Kousha, K. and Thelwall, M. (2007)
The Web impact of open access social science research (full-text requires subscription; otherwise abstract only)
Library & Information Science Research, Volume 29, Issue 4, December 2007, 495-507, available online 15 October 2007
preprint http://www.scit.wlv.ac.uk/~cm1993/papers/OpenAccessSocialSciencePreprint.doc (.doc 12pp)
From the abstract: "The results suggest that new types of citation information and informal scholarly indictors could be extracted from the Web for the social sciences."

Added 17 December 2007 Dietrich, J. P. (2007)
The Importance of Being First: Position Dependent Citation Rates on arXiv:astro-ph
arXiv.org, arXiv:0712.1037v1 [astro-ph], 6 December 2007, in Publications of the Astronomical Society of the Pacific, 120 (864): 224-228, February 2008
From the abstract: "We study the dependence of citation counts of e-prints published on the arXiv:astro-ph server on their position in the daily astro-ph listing. ... cannot exclude that increased visibility at the top of the daily listings contributes to higher citation counts as well."

Added 13 September 2007 Kurtz, M. J. and Henneken, E. A. (2007)
Open Access does not increase citations for research articles from The Astrophysical Journal
arXiv.org, arXiv:0709.0896v1 [cs.DL], 6 September 2007
Abstract: We demonstrate conclusively that there is no "Open Access Advantage" for papers from the Astrophysical Journal. The two to one citation advantage enjoyed by papers deposited in the arXiv e-print server is due entirely to the nature and timing of the deposited papers. This may have implications for other disciplines.

Added 22 August 2007 Sotudeh, H. and Horri, A. (2007)
The citation performance of open access journals: A disciplinary investigation of citation distribution models (full-text subscribers only; no abstract)
Journal of the American Society for Information Science and Technology, Vol. 58, No. 13, 2007, 2145-2156, published online August 17, 2007
From the conclusion: "To sum up, the similarity of the science system across OAJ and NOAJ boundaries has been confirmed. We see this as further evidence of OA's widespread recognition by scientific communities. However, because the magnitudes of the exponents found in this study are lower than what was previously observed for the whole system, OA may currently perform at a slightly lower level. According to the models used in this study, the citation distributions between fields are strongly disproportionate in Life Sciences and Engineering and Material Sciences, favoring larger fields in the former, but smaller fields in the latter. However, the distributions tend to be rather linear in the Natural Sciences."

Added 22 August 2007 Lin, S.-K. (2007)
Editorial: Non-Open Access and Its Adverse Impact on Molecules
Molecules, 12, 1436-1437, 16 July 2007
The point of this short editorial is clear, that the difference between the OA and non-OA content in the journal Molecules is clearly reflected in higher citations for the former. The context could be clearer, however. The OA/non-OA history of the journal, especially prior to the period under review (2005-6), is not elaborated and familiarity with the journal is assumed.

Added 22 August 2007 Taylor, D. (2007)
Looking for a Link: Comparing Faculty Citations Pre and Post Big Deals
Electronic Journal of Academic and Special Librarianship, v.8 no.1 (Spring 2007)
Note. The Big Deal is where a library or consortium of libraries subscribes to a larger package of a publisher's journals than they would have if they had subscribed to journals individually. Big Deals are claimed to improve access for an institution's users. "Pre Big Deal, the percentage of citations to journals that are part of Big Deals but were previously not subscribed to was an average of 2.6%. Post Big Deal this increased to an average of 6.1%." There is no analysis or comment on how this result might be affected if it was considering open access.

Added 10 May 2007 Tonta, Y., Ünal, Y. and Al, U. (2007)
The Research Impact of Open Access Journal Articles
E-LIS, 30 April 2007, also in Proceedings ELPUB 2007, the 11th International Conference on Electronic Publishing, Vienna, 13-15 June 2007

Added 10 May 2007 Piwowar, H. A., Day, R. S. and Fridsma, D. B. (2007)
Sharing Detailed Research Data Is Associated with Increased Citation Rate
PLoS ONE, March 21, 2007
Principal Findings: "We examined the citation history of 85 cancer microarray clinical trial publications with respect to the availability of their data. The 48% of trials with publicly available microarray data received 85% of the aggregate citations. Publicly available data was significantly (p = 0.006) associated with a 69% increase in citations, independently of journal impact factor, date of publication, and author country of origin using linear regression."

Added 8 March 2007 Bergstrom, T. C. and Lavaty, R. (2007)
How often do economists self-archive?
eScholarship Repository, University of California, February 8, 2007

Added 26 May 2008 Chapman, S., Nguyen, T. N. and White, C. (2007)
Press-released papers are more downloaded and cited (full text requires subscription; extract only)
Tobacco Control, 16 (1): 71-71, February 2007

Added 22 January 2007 Harnad, S. and Hajjem, C. (2007)
The Open Access Citation Advantage: Quality Advantage Or Quality Bias?
Author blog, Open Access Archivangelism, 21 January 2007
Does the OA Advantage (OAA) occur because authors are more likely to self-selectively self-archive articles that are more likely to be cited (self-selection "Quality Bias": QB), or because articles that are self-archived are more likely to be cited ("Quality Advantage": QA)? Preliminary evidence based on over 100,000 articles from multiple fields, comparing self-selected self-archiving with mandated self-archiving to estimate the contributions of QB and QA to the OAA shows: "Both factors contribute, and the contribution of QA is greater." Includes comment on Moed, H. (2006), The effect of 'Open Access' upon citation impact: An analysis of ArXiv's Condensed Matter Section.

Added 28 July 2008 Knowlton, S. A. (2007)
Continuing use of print-only information by researchers
J Med Libr Assoc., 95(1): 83-88, January 2007
"to study the question, "Are researchers still accessing and using material issued only in print?," a group of journals was selected, and the impact factor of each was tracked over the period 1993-2003.
Conclusion: the online status of a journal is not sufficient to override all other considerations by researchers when they choose which material to cite."

Added 19 November 2006 Moed, H. F. (2006)
The effect of 'Open Access' upon citation impact: An analysis of ArXiv's Condensed Matter Section
ArXiv, Computer Science, cs.DL/0611060, 14 November 2006, in Journal of the American Society for Information Science and Technology, Vol. 58, No. 13, 2007, 2145-2156, published online August 30, 2007 http://dx.doi.org/10.1002/asi.20663 (subscriber access only to full text)
"This article statistically analyses how the citation impact of articles deposited in the Condensed Matter section of the preprint server ArXiv, and subsequently published in a scientific journal, compares to that of articles in the same journal that were not deposited in that archive. Its principal aim is to further illustrate and roughly estimate the effect of two factors, 'early view' and 'quality bias', upon differences in citation impact between these two sets of papers ... The analysis provided evidence of a strong quality bias and early view effect. Correcting for these effects, there is in a sample of 6 condensed matter physics journals studied in detail, no sign of a general 'open access advantage' of papers deposited in ArXiv. The study does provide evidence that ArXiv accelerates citation, due to the fact that that ArXiv makes papers earlier available rather than that it makes papers freely available."

Comment on this paper:
Harnad, S. (2007), The Open Access Citation Advantage: Quality Advantage Or Quality Bias?, Open Access Archivangelism, 21 January 2007
Moed, H. (2006) reply on OA to sigmetrics, SIGMETRICS list server, 8 December 2006: On Quality bias. (Harnad) wrote: "The fact that highly-cited articles (Kurtz) and articles by highly-cited authors (Moed) are more likely to be Arxived certainly does not settle the question of cause and effect: It is just as likely that better articles benefit more from Arxiving (QA) as that better authors/articles tend to Arxive/be-Arxived more (QB)". Citation rates may be influenced both by the 'quality' of the papers and by the access modality (deposited versus non-deposited). This is why I estimated author prominence on the basis of the citation impact of their non-archived articles only. But even then I found evidence that prominent, influential authors (in the above sense) are overrepresented in papers deposited in ArXiv. But I did more that that. I calculated Arxiv Citation Impact Differentials (CID) at the level of individual authors. Next, I calculated the median CID over authors publishing in a journal. How then do you explain my empirical finding that for some authors the CID is positive, for others it is negative, while the median CID over authors does not significantly differ from zero (according to a Sign test) for all journals studied in detail except Physical Review B, for which it is only 5 per cent? If there is a genuine 'OA advantage' at stake, why then does it for instance not lead to a significantly positive median CID over authors? Therefore, my conclusion is that, controlling for quality bias and early view effect, in the sample of 6 journals analysed in detail in my study, there is no sign of a general 'open access advantage' of papers deposited in ArXiv's Condensed Matter Section. ... I hope that more case studies will be carried out in the near future, applying the methodologies I proposed in my paper.
Harnad, S. (2006) The Self-Archiving Impact Advantage: Quality Advantage or Quality Bias?, Open Access Archivangelism, 20 November 2006

Added 19 November 2006 Henneken, E. A., Kurtz, M. J., Warner, S., Ginsparg, P., Eichhorn, G., Accomazzi, A., Grant, C. S., Thompson, D., Bohlen, E. and Murray, S. S. (2006)
E-prints and Journal Articles in Astronomy: a Productive Co-existence
ArXiv, Computer Science, cs.DL/0609126, 22 September 2006, in Learned Publishing, Vol. 20, No. 1, January 2007, 16-22

Added 09 March 2010 Kurtz, M. and Brody, T. (2006)
The impact loss to authors and research
e-Prints Soton, 12 July 2006, in Jacobs, N. (ed.), Open Access: Key strategic, technical and economic aspects (Oxford, UK: Chandos Publishing)

Added 03 August 2006 Metcalfe, T. S. (2006)
The Citation Impact of Digital Preprint Archives for Solar Physics Papers
Solar Physics, Vol. 239, No. 1-2, December 2006, pp. 549-553
also in ArXiv, Astrophysics, astro-ph/0607079, 5 July 2006 http://arxiv.org/abs/astro-ph/0607079
"Most astronomers now use the arXiv.org server (astro-ph) to distribute preprints, but the solar physics community has an independent archive hosted at Montana State University. For several samples of solar physics papers published in 2003, I quantify the boost in citation rates for preprints posted to each of these servers. I show that papers on the MSU archive typically have citation rates 1.7 times higher than the average of similar papers that are not posted as preprints, while those posted to astro-ph get 2.6 times the average. A comparable boost is found for papers published in conference proceedings, suggesting that the higher citation rates are not the result of self-selection of above-average papers."

Added 03 August 2006 Henneken, E. A., Kurtz, M. J., Eichhorn, G., Accomazzi, A., Grant, C., Thompson, D., and Murray, S. S. (2006)
Effect of E-printing on Citation Rates in Astronomy and Physics
Journal of Electronic Publishing, Vol. 9, No. 2, Summer 2006, also in ArXiv, Computer Science, cs.DL/0604061, v2, 5 June 2006 http://arxiv.org/abs/cs/0604061
"It has been observed that papers that initially appear as arXiv e-prints get cited more than papers that do not. Using the citation statistics from the NASA-Smithsonian Astrophysics Data System, we confirm the findings from other studies, we examine the average citation rate to e-printed papers in the Astrophysical Journal, and we show that for a number of major astronomy and physics journals the most important papers are submitted to the arXiv e-print repository first.

Added 03 August 2006 Kousha, K. and Thelwall, M. (2006)
Google Scholar Citations and Google Web/URL Citations: A Multi-Discipline Exploratory Analysis
E-LIS, 05 June 2006, also in Proceedings International Workshop on Webometrics, Informetrics and Scientometrics & Seventh COLLNET Meeting, Nancy (France), May 2006
"we built a sample of 1,650 articles from 108 Open Access (OA) journals published in 2001 in four science and four social science disciplines. We recorded the number of citations to the sample articles using several methods based upon the ISI Web of Science, Google Scholar and the Google search engine (Web/URL citations). For each discipline, we found significant correlations between ISI citations and both Google Scholar and Google Web/URL citations; with similar results when using total or average citations, and when comparing within and across (most) journals."

Added 16 May 2006 Eysenbach, G. (2006)
Citation Advantage of Open Access Articles
PLoS Biology, Volume 4, Issue 5, May 2006
Further evidence for the OA citation advantage, although quite critical of other studies with which its findings broadly agree. This example is based on a small, single journal sample (PNAS: Proceedings of the National Academy of Sciences). Since PNAS offers authors the choice of paying to provide open access to published papers and/or freely self-archiving, a 'Secondary analysis' considers the relative impact of each type of OA, although the number of papers involved is really too small to give this result the weight of the broader findings. The paper is accompanied by two editorials, one in the publishing journal, the other a self-published editorial by the author:
MacCallum, C. J. and Parthasarathy, H. (2006) Editorial: Citation Advantage of Open Access Articles, PLoS Biology, Volume 4, Issue 5, May 2006
Eysenbach, G. (2006) The Open Access Advantage, Journal of Medical Internet Research, 2006;8(2):e8

Comment on this paper:
Harnad, S. on Chronicle of Higher Education News Blog on this paper, 15 May 2006: "The Eysenbach study is certainly not "the first to compare open-access and non-open-access papers from the same journal". See [this bibliography]"
Harnad, S. eLetter, PLoS, Pipe-Dreams and Peccadillos, on the PLoS editorial, 16 May 2006: "There can be disagreement about what evidence one counts as "solid," but there can be little dispute that prior evidence derived from substantially larger and broader-based samples showing substantially the same outcome can hardly be described as "surprisingly hard to find". The only new knowledge from this small, journal-specific sample was (1) the welcome finding of how early the OA advantage can manifest itself, plus (2) some less clear findings about differences between first- and last-author OA practices, plus (3) a controversial finding that will most definitely need to be replicated on far larger samples in order to be credible: "The analysis revealed that self-archived articles are also cited less often than OA articles from the same journal.""
Author's response eLetter, PLoS, 17 May 2006: "None of the previous papers in [this bibliography] employed a similar methodology, working with data from a "gold-OA" journal. ... Regarding "larger samples" I think rigor and quality (leading to internal validity) is more important than quantity (or sample size). Going through the laborious effort to extract article and author characteristics for a limited number of articles (n=1492) in order to control for these confounders provides scientifically stronger evidence than doing a crude, unadjusted analysis of a huge number of online accessible vs non-online accessible articles, leaving open many alternative explanations. ... contrary to what Harnad said, this study is NOT at all "showing substantially the same outcome". On the contrary, the effect of green-OA -- once controlled for confounders -- was much less than what others have claimed in previous papers."
Harnad, S. blog, Confirming the Within-Journal OA Impact Advantage, 18 May 2006: "with the large, consistent within-journal OA/NOA differences found across all journals, all disciplines and all years in samples four orders of magnitude larger than Eysenbach's, it is not at all clear that controls for those "multiple confounders" are necessary in order to demonstrate the reality, magnitude and universality of the OA advantage. That does not mean the controls are not useful, just that they are not yet telling us much that we don't already know. ... the true measure of the SOA (Self-Archived OA) advantage today (at its 15% spontaneous baseline) is surely not to be found in PNAS but in the statistically far more numerous, hence far more representative full-spectrum of journals that do not yet offer POA (Payed OA). (I would be delighted if those journals took the Eysenbach findings as a reason for offering a POA option! But not at the expense of authors drawing the absurd conclusion -- not at all entailed by Eysenbach's PNAS-specific results -- that in the journals they currently publish in, SOA alone would not confer citation advantages at least as big as the ones we have been reporting.)"
Author's response WebCite blog, The OA debate between an "rchivangelist" and an OA researcher, 24 May 2006: ""Confounded" associations between two variables which falsely suggests causality can ONLY be ruled out if one controls for the confounder no matter how "strong, consistent" the effect appears ... Our "events" (citations) are determined by many different "causes", of which "access" is only one variable - many other variables, including confounders, have to be taken into account.
Harnad, S. blog, The Epidemiology of OA, 26 May 2006: considers each of Eysenbach's list of confounders, which ones might have an effect and which ones will be tested. "Stay tuned..."
Suber, P. SPARC Open Access Newsletter, issue #98, Gunther Eysenbach confirms the OA impact advantage, 2 June 2006: "There's some controversy about whether some earlier results, especially by Tim Brody, Chawki Hajjem, and Stevan Harnad, are the same or only similar to some of Eysenbach's results. But no one doubts that Eysenbach has new and valid results, or that he has persuasively advanced the case that OA helps authors and journals build their citation impact. While there have been many previous studies of the OA impact advantage, none has made the splash that Eysenbach's has."
Davis, P. Citation advantage of Open Access articles likely explained by quality differential and media effects, PLoS Biology, Responses, 16 January 2007: "The fact that OA articles were more likely to be featured on the front cover of PNAS and covered by the media suggests that other causal explanations may explain the OA advantage. Open Access may be a result - not a cause of - a quality differential which is amplified by the media. While Eysenbach's attempt to control other explanatory variables was excellent, what is needed are true randomized controlled studies of OA publishing."
Harnad, S. blog, Citation Advantage For OA Self-Archiving Is Independent of Journal Impact Factor, Article Age, and Number of Co-Authors, 17 January 2007: "Chawki Hajjem has now done a multiple regression analysis jointly testing (1) article age, (2) journal impact factor, (3) number of authors, and (4) OA self-archiving as separate factors for 442,750 articles in 576 (biomedical) journals across 11 years, and has shown that each of the four factors contributes an independent, statistically significant increment to the citation counts. The OA-self-archiving advantage remains a robust, independent factor.

Comment on this paper:
Authors Self-Selection bias "While our study confirms the same citation advantage reported by others, it does not attribute Open Access as the cause of more citations, but to Self-Selection. Open Access therefore may be a result, not a cause, of authors promoting higher-quality work."
Liblicense, 14 March 2006
Harnad, S. OAA a causal factor "I think your results are very interesting, but I don't think they have shown that the OA citation advantage (OAA) is all or mostly a self-selection Quality Bias (QB) correlate, rather than being causal. It is still quite plausible that the OAA is a genuine causal factor, but that it has a bigger effect on the high quality/citation end."
SIGMETRICS, 14 March 2006
Qualifying statements: Authors "I am however, troubled by individuals who make universal and unqualified statements like, "Open Access increases citations by 50-250%!"" Harnad, S. "I am such an individual, and I hold by that statement" Authors "The more precise answer is much more subtle, but I understand that a statement like, "open access may provide some citation benefit, but only for prestigious authors who publish in prestigious journals and whose article is already highly-cited", doesn't sound as convincing to administrators and policy makers." Harnad, S. "I don't think it is a correct statement of the thrust of the current body of findings on the OAA. It is merely your interpretation of the result of your own study in 4 maths journals!"
SIGMETRICS, 15 March 2006
Causation or association?: Antelman, K. "Data I collected for philosophy, political science, engineering and mathematics do not support this hypothesis that OA causes more citations for better articles only ... at that time I had not looked at the distribution of OA and non-OA articles by citations. Graphs of those results are posted at http://www.lib.ncsu.edu/staff/kantelman/OA_by_citations.xls. These data show OA citation advantage across all articles with more than zero citations. Authors "The data that Kristin illustrates do not show causation, only association." Harnad, S. The data Phil illustrates likewise do not show causation, only association. ... More fine-tuned causal tests are needed to decide.
Liblicense, from 20 March 2006

Added 03 August 2006 Mueller, P. S., Murali, N. S., Cha, S. S., Erwin, P. J. and Ghosh, A. K. (2006)
The effect of online status on the impact factors of general internal medicine journals
Netherlands Journal of Medicine, 64 (2): 39-44, February 2006
"becoming available online as FUTON (full text on the Net) is associated with a significant increase in journal impact factor."

Added 30 December 2005 Hajjem, C., Harnad, S. and Gingras, Y. (2005)
Ten-Year Cross-Disciplinary Comparison of the Growth of Open Access and How it Increases Research Citation Impact (pdf 8pp)
IEEE Data Engineering Bulletin, Vol. 28 No. 4, December 2005
also Author eprint, 16 December 2005 http://eprints.ecs.soton.ac.uk/11688/
"In 2001, Lawrence found that articles in computer science that were openly accessible (OA) on the Web were cited substantially more than those that were not. We have since replicated this effect in physics. To further test its cross-disciplinary generality, we used 1,307,038 articles published across 12 years (1992-2003) in 10 disciplines (Biology, Psychology, Sociology, Health, Political Science, Economics, Education, Law, Business, Management). The overall percentage of OA (relative to total OA + NOA) articles varies from 5%-16% (depending on discipline, year and country) and is slowly climbing annually. Comparing OA and NOA articles in the same journal/year, OA articles have consistently more citations, the advantage varying from 25%-250% by discipline and year."

Added 30 December 2005 Hajjem, C., Gingras, Y., Brody, T., Carr, L. and Harnad, S. (2005)
Open Access to Research Increases Citation Impact (.doc 12pp)
Author eprint, 16 December 2005, Technical Report, Institut des sciences cognitives, Université du Québec à Montréal

Added 30 December 2005 Sahu, D.K., Gogtay, N.J. and Bavdekar, S.B. (2005)
Effect of open access on citation rates for a small biomedical journal
Author eprint, December 1, 2005, in Fifth International Congress on Peer Review and Biomedical Publication, Chicago, September 16-18, 2005
"We assessed the influence of OA on citations rates for a small, multi-disciplinary journal which adopted OA without article submission or article access fee. DESIGN The full text of articles published since 1990 were made available online in 2001. Citations for these articles as retrieved using Web of Science, SCOPUS, and Google Scholar were divided into two groups - the pre-OA period (1990-2000) and the post-OA period (2001-2004). CONCLUSIONS Open access was associated with increase in the number of citations received by the articles. It also decreased the lag time between publication and the first citation. For smaller biomedical journals, OA could be one of the means for improving visibility and thus citation rates."

Added 27 September 2005 Zhao, D. (2005)
Challenges of scholarly publications on the Web to the evaluation of science -- A comparison of author visibility on the Web and in print journals (abstract only)
Information Processing and Management, 41:6, 1403-1418, December 2005
Compares author visibility between the Web and print journals as revealed from citation analysis based on a search for the term "XML" or "eXtensible Markup Language" using NEC Research Institute's CiteSeer, the entire ISI Science Citation Index (SCI) database, and journals indexed and classified in SCI as representing computer science research. The main finding: "The author ranking by number of citations that resulted from CiteSeer data is highly correlated with that obtained from SCI." i.e. it's not comparing OA impact vs non-OA but Web vs journal, and finds that authors, notably the top authors, are self-archiving and publishing papers in both places.

Added 11 February 2008 Coats, A. J. S. (2005)
Top of the charts: download versus citations in the International Journal of Cardiology (full-text requires subscription; otherwise abstract only)
International Journal of Cardiology, Volume 105, Issue 2, 2 November 2005, 123-125, available online 7 October 2005
From the abstract: "We have recorded the 10 top cited articles over a 12-month period and compared them to the 10 most popular articles being downloaded over the same time period. The citation-based listing included basic and applied, observational and interventional original research reports. For downloaded articles, which have shown a dramatic increase for the International Journal of Cardiology from 48,000 in 2002 to 120,000 in 2003 to 200,000 in 2004, the most popular articles over the same period are very different and are dominated by up-to-date reviews of either cutting-edge topics (such as the potential of stem cells) or of the management of rare or unusual conditions. There is no overlap between the two lists despite covering exactly the same 12-month period and using measures of peer esteem. Perhaps the time has come to look at the usage of articles rather than, or in addition to, their referencing."

Added 13 July 2005 Adams, J. (2005)
Early citation counts correlate with accumulated impact (abstract only)
Scientometrics, 63 (3): 567-581, June 2005
Working towards earlier prediction of impact. This paper is not OA and has just appeared but was written before Brody et al. (2005) revealed a correlation to predict impact from even earlier data, i.e. download data for OA papers, before any citations.

Added 26 September 2005 Moed, H. F. (2005)
Statistical Relationships Between Downloads and Citations at the Level of Individual Documents Within a Single Journal (abstract only)
Journal of the American Society for Information Science and Technology, 56(10): 1088-1097, published online 31 May 2005
"Statistical relationships between downloads from ScienceDirect of documents in Elsevier's electronic journal Tetrahedron Letters and citations to these documents recorded in journals processed by the (ISI) for the Science Citation Index (SCI) are examined. ... Findings suggest that initial downloads and citations relate to distinct phases in the process of collecting and processing relevant scientific information that eventually leads to the publication of a journal article." Does not investigate open access sources. Notes the need for caution in drawing conclusions on the frequency of paper downloads from formal citation patterns, and vice versa.

Added 28 July 2008 De Groote, S. L., Shultz, M. and Doranski, M. (2005)
Online journals' impact on the citation patterns of medical faculty J Med Libr Assoc., 93 (2): 223-228, April 2005
From the conclusion: "It is possible that electronic access to information (i.e., online databases) has had a positive impact on the number of articles faculty will cite. Results of this study suggest, at this point, that faculty are still accessing the print-only collection, at least for research purposes, and are therefore not sacrificing quality for convenience."

Added 03 August 2006 Metcalfe, T. S. (2005)
The Rise and Citation Impact of astro-ph in Major Journals
ArXiv, Astrophysics, astro-ph/0503519, 23 March 2005
"I describe a simple method to determine the adoption rate and citation impact of astro-ph over time for any journal using NASA's Astrophysics Data System (ADS). I use the ADS to document the rise in the adoption of astro-ph for three major astronomy journals, and to conduct a broad survey of the citation impact of astro-ph in 13 different journals. I find that the factor of two boost in citations for astro-ph papers is a common feature across most of the major astronomy journals."

Updated 13 April 2005 Ongoing studies Hajjem, C. (2004-05)
Cover page for the range of studies highlighted below, Laboratoire de recherche en Sciences Cognitives, UQAM. (Text in French but graphs "self-explanatory"; see this comment for elaboration)

Updated 31 January 2005 Schwarz, G. and Kennicutt Jr., R. C. (2004)
Demographic and Citation Trends in Astrophysical Journal Papers and Preprints (pdf 14pp)
Arxiv.org, astro-ph/0411275, 10 November 2004, Bulletin of the American Astronomical Society, Vol. 36, 1654-1663
See also a note from AAS Pub Board meeting, Tucson, November 3-4 2003
"Greg Schwarz (from the ApJ editorial office) reported some work he's doing tracking citation rates of papers published in the ApJ based on whether they were posted on astro-ph or not: ApJ papers that were also on astro-ph have a citation rate that is _twice_ that of papers not on the preprint server"
http://listserv.nd.edu/cgi-bin/wa?A2=ind0311&L=pamnet&D=1&O=D&P=1632

Added 03 August 2006 Havemann, F. (2004)
Eprints in der wissenschaftlichen kommunikation (Eprints in scientific communication)
Author eprint, 26 October 2004, presented at the Institute of Library Science, Humboldt University, Berlin, June 1, 2004
"the use of eprints can significantly accelerate the scientific communication. This was demonstrated by me with a small sample of articles in theoretical High Energy Physics published 1998 and 1999 in Physical Review D. Typically the eprints in this sample are available eight months before the printed issue is published. Three quarters of them are cited in eprints authored by other researchers before the journal issue appears (among them all highly cited eprints)."

Added 17 May 2010 Comment on this paper:
Davis, P., Do Open-Access Articles Really have a Greater Research Impact? Letter to the editor, College & Research Libraries, Vol. 67, No. 2, March 2006: "The study of citation behavior is complex and involves multiple confounding, and interacting variables. Methodologically, it is very difficult to distinguish whether Open Access is an explanatory cause of increased access, or whether it is merely an artifact of other causal explanations such as article duplication or self-promotion. Do Open Access articles really have a greater research impact, as Antelman suggests? Yes, but Open Access may not be the cause."
Author's response: "While I intentionally phrased my conclusion as an association, rather than a causation (open-access articles have a greater research impact than articles that are not freely available), there clearly is an implied causation and I should have been more explicit that the data do not support that. The article was very much a product of its time, however, when there was little solid data that there even was an association between open access and increased citations. ... Since I did the study in C&RL, I have collected additional data that indicate that quality bias is real and significant, at least in the social sciences."
Davis, P.: In 2005, Wren conducted a massive automated study of the availability of author reprints on the public web. He reported two main conclusions: that articles available freely online yielded more citations; and that there was a high degree of association between high-prestige journals and frequency of author reprints. Journals with high Impact Factors (New England Journal of Medicine, Nature, Science, and Cell) were associated with a higher degree of author republishing than lower-impact journals. Wren went further to discuss possible causes of this difference and briefly discusses a trophy effect the desire for researchers to display their accomplishments which would explain why high impact publications are more common online. This is consistent with Antelmans findings, that the greatest impact of open access is with the most-cited articles.
Antelman, K.: Wren's study needs to be looked at carefully, however, because he did not look at the source of the open access copies he found, so the extent of trophy effect self-archiving cannot be assessed from his data. I also collected some data on the source of open access copies from three of the high-impact journals he looked atNEJM, Science and Natureand, while many articles from those journals are freely available online, many or most are not posted by the authors themselves, in particular, NEJM where only 12% of the open access articles were posted by authors or their institutions."

Added 13 April 2005 Murali, N. S., Murali, H. R., Auethavekiat, P., Erwin, P. J., Mandrekar, J. N., Manek, N. J. and Ghosh, A. K. (2004)
Impact of FUTON and NAA Bias on Visibility of Research
Mayo Clinic Proceedings, Vol. 79, No. 8, 1001-1006, August 2004
Notes and comment: FUTON = full text on the Net; NAA = no abstract available
This is not an article on how Open Access increases impact but on how *Online* Access increases impact. The effects are related, but one is a licensing effect, not an OA effect.

Kurtz, M. J., Eichhorn, G., Accomazzi, A., Grant, C., Demleitner, M., Murray, S. S., Martimbeau, N. and Elwell, B. (2003b)
The NASA Astrophysics Data System: Sociology, Bibliometrics, and Impact
Author eprint, March 2003, Journal of the American Society for Information Science and Technology, submitted for publication

Added 5 December 2012 Brown, C. (2003)
The role of electronic preprints in chemical communication: Analysis of citation, usage, and acceptance in the journal literature
Journal of the American Society for Information Science, Vol. 54, No. 5, 362-371, published online 6 Feb 2003
This study characterizes the usage and acceptance of electronic preprints (e-prints) in the literature of chemistry. Survey of authors of e-prints appearing in the Chemistry Preprint Server (CPS) at http://preprints.chemweb.com indicates use of the CPS as a convenient vehicle for dissemination of research findings and for receipt of feedback before submitting to a peer-reviewed journal. Reception of CPS e-prints by editors of top chemistry journals is very poor. Only 6% of editors responding allow publication of articles that have previously appeared as e-prints. Consequently, it was not surprising to discover that citation analysis yielded no citations to CPS e-prints in the traditional literature of chemistry.

Added 17 December 2007 Drenth, J. P. H. (2003)
More reprint requests, more citations? (subscriber access to full text)
Scientometrics, Vol. 56, No. 2, February 2003, 283-286, revised version published online August 2006
From the abstract: "This study aims to correlate the number of reprint requests from a 10-year-sample of articles with the number of citations. ... Articles that received most reprint requests are cited more often."

Kurtz, M. J., Eichhorn, G., Accomazzi, A., Grant, C. S., Thompson, D. M., Bohlen, E. H. and Murray, S. S. (2002)
The NASA Astrophysics Data System: Obsolescence of Reads and Cites (pdf 8pp)
Library and Information Services in Astronomy IV, edited by B. Corbin, E. Bryson, and M. Wolf, July 2002

Added 5 December 2012 Curti, M., Pistotti, V., Gabutti, G. and Klersy, C. (2001)
Impact factor and electronic versions of biomedical scientific journals
Haematologica, Vol. 86, No. 10, Oct 2001, 1015-1020
From the Abstract: The availability of journals (table of contents (TOC), abstracts, full text and free full text) on Internet, in years 1995-2000, was assessed between December 2000 and January 2001. The first 20 top-journals from 8 subject categories were included. Changes in impact factor over time and association with Internet availability were modeled. RESULTS: Overall, 118/139 journals (85%) had their TOC on the Internet, of these 107 (77%) had abstracts, 97 (70%) had full text and 33 (24%) free full text. The median impact factor for all journals was 1.65, 2.08, 2.10, 2.21 and 2.35 for the years from 1995 to 1999, respectively. This increase was statistically significant, with differences among subject categories. The presence of TOC, abstracts and full text on the Internet was also significantly associated with higher impact factor, after accounting for time and subject category. INTERPRETATION AND CONCLUSIONS: The impact factor has been used for assessing the quality of journals. We identified a new limitation of this indicator: the impact factor seems to be related to the amount of circulation of information through Internet. This could be a temporary limitation, associated with diffusion of journals on, and spread of Internet.

Lawrence, S. (2001)
Free online availability substantially increases a paper's impact
Nature, 31 May 2001
see also Online or invisible, an extended version of the Nature article self-archived by the author
The first major findings on the impact effect documented in this bibliography, it remains the most cited paper in the bibliography. Note, its results concern online access rather than open access. At that time the focus was on the transition from print to electronic publication, with Lawrence quantifying the improved access that resulted based on a sample of c.120k computer science papers from 1,494 'venues'.

Added 04 October 2005 Anderson, K., Sack, J., Krauss, L. and O'Keefe, L. (2001)
Publishing Online-Only Peer-Reviewed Biomedical Literature: Three Years of Citation, Author Perception, and Usage Experience
Journal of Electronic Publishing, Vol. 6, No. 3, March 2001
One of the first studies of the citation effect of online against offline publication, rather than of open access against non-OA. Provides data for one journal and a small number of articles over a three year period year. This paper was added to the bibliography following this correspondence:

Added 5 December 2012 Brown, C. (2000)
The E-volution of preprints in the scholarly communication of physicists and astronomers
Journal of the American Society for Information Science, Vol. 52 No. 3, 187-200, published online 30 Nov 2000
From the Abstract: To learn how e-prints are cited, used, and accepted in the literature of physics and astronomy, the philosophies, policies, and practices of top-tier physics and astronomy journals regarding e-prints from the Los Alamos e-print archive, arXiv.org, were examined. Citation analysis illustrated e-prints were cited with increasing frequency by a variety of journals in a wide range of physics and astronomy fields from 1998 to 1999. Even though the policies concerning e-print citation and publication were inconsistent, the number of citations (35,928) and citations rates (34.1%) to 12 arXiv.org archives were found to be large and increasing.

Updated 04 October 2005 Odlyzko, A. M. (2000)
The rapid evolution of scholarly communication
PEAK 2000: Economics and Usage of Digital Library Collections conference, Ann Arbor, MI, March 2000.
Also in Learned Publishing, 15(1), 7-19, January 2002 here. Author eprint http://www.dtc.umn.edu/~odlyzko/doc/rapid.evolution.pdf
Notes the growing usage of information in electronic form (c.f. print forms) and of journal papers from non-journal sites (e.g. eprints), and presents evidence that usage increases when access is more convenient

Web tools for measuring impact

Elsevier Scopus Bibliographic database covering 13,450 peer-reviewed titles http://www.scopus.com/ User service
see
Added 28 July 2008 Jacsó, P. (2007) Scopus (2008 Winter Release), Gale, Reference Reviews, Péter's Digital Reference Shelf, November 2007
Added 15 March 2006 Burnham, J. F. (2006) Scopus database: a review, Biomedical Digital Libraries, 3:1, 8 March 2006
Added 15 March 2006 Dess, H. M. (2006) Scopus, Issues in Science and Technology Librarianship, Winter 2006
Added 15 May 2006 Quint, B. (2006) Elsevier's Scopus Introduces Citation Tracker: Challenge to Thomson ISI's Web of Science?, Newsbreaks, January 23, 2006
Added 13 September 2007 Goodman, D. and Deis, L. (2006) Update on Scopus, The Charleston Advisor, Vol. 7, No. 3, January 2006, 42-43
Jacsó, P. (2004) Scopus, Thomson Gale, September 2004
see also Comparative reviews

Added 11 December 2006 Rexa.Info Covers the computer science research literature. Rexa is "a sibling to CiteSeer, Google Scholar, Academic.live.com, the ACM Portal. It's chief enhancement is that Rexa knows about more first-class, de-duplicated, cross-referenced object types: not only papers and their citation links, but also people, grants, topics" http://rexa.info/ User service, free (login required)

Added 13 April 2006 Windows Live Search Academic Beta version. Indexes content related to computer science, physics, electrical engineering, and related subject areas, with more than 6 million records from approximately 4300 journals, 2000 conferences and ArXiv.org. In collaboration with Citeseer http://academic.live.com/ User service, free
see
Added 26 May 2008 Nadella, S. (2008) Book search winding down, Live Search, The official blog of the Live Search team at Microsoft, May 23, 2008
"Live Search Books and Live Search Academic projects ... will be taken down next week. Books and scholarly publications will continue to be integrated into our Search results, but not through separate indexes."
Added 28 July 2008 Jacsó, P. (2008) Live Search Academic, Gale, Reference Reviews, Péter's Digital Reference Shelf, April 2008
Added 28 July 2008 Jacsó, P. (2006) Windows Live Academic, Online, Sep/Oct 2006, 59-60
Added 15 May 2006 Quint, B. (2006) Windows Live Academic Search: The Details, Newsbreaks, April 17, 2006
Added 13 April 2006 Sherman, C. (2006) Microsoft Launches Windows Live Academic Search, SearchEngineWatch.com, April 12, 2006

Added 15 May 2006 Citations in Economics not intended for direct user access; instead is made available to RePEc services such as Socionet, EconPapers and IDEAS. Uses Citeseer software http://citec.repec.org/ Data service, free
Rank working papers series and journals in Economics http://citec.repec.org/s/
see
Barrueco Cruz, J. M. and Krichel, T. (2004) Building an autonomous citation index for grey literature: the economics working papers case (pdf 12pp), E-LIS, 01 February 2005, also in Proceedings GL6: Sixth International Conference on Grey Literature, New York, December 2004

CrossRef Forward linking service tool allows CrossRef member publishers to display cited-by links in their primary content, Data service
CrossRef and Atypon announce forward linking service (press release) June 8, 2004
Institute of Physics becomes first journals publisher to implement 'cited-by' links using CrossRef's Forward Linking service: Time travel with IOP journals (IOP press release) 14 March, 2005

Added 13 January 2009 Norris, M., Oppenheim, C. and Rowland, F. (2008)
Finding open access articles using Google, Google Scholar, OAIster and OpenDOAR
Online Information Review, Vol. 32, No. 6, 2008, 709-715
also available from Loughborough University Institutional Repository, 2009-01-12 http://hdl.handle.net/2134/4084
From the abstract: "Google, Google Scholar, OAIster and OpenDOAR were used to try to locate OA versions of peer reviewed journal articles drawn from three subjects (ecology, economics, and sociology). The paper shows the relative effectiveness of the search tools in these three subjects. The results indicate that those wanting to find OA articles in these subjects, for the moment at least, should use the general search engines Google and Google Scholar first rather than OpenDOAR or OAIster."

Added 28 July 2008 Jacsó, P. (2008)
The Plausibility of Computing the H-index of Scholarly Productivity and Impact Using Reference Enhanced Databases
Online Information Review, 32(2) 2008, 266-283
"aims to provide a general overview of the three largest, cited-reference-enhanced, multidisciplinary databases (Google Scholar, Scopus, and Web of Science) for determining the h-index. The practical aspects of determining the h-index also need scrutiny, because some content and software characteristics of reference-enhanced databases can strongly influence the h-index values."

Added 13 September 2007 Goodman, D. and Deis, L. (2007) Update on Scopus and Web of Science, The Charleston Advisor, Vol. 8, No. 3, January 2007, 15-18

Added 10 May 2007 Meho, L. I. and Yang, K. (2006) A New Era in Citation and Bibliometric Analyses: Web of Science, Scopus, and Google Scholar, arXiv.org, Computer Science, cs/0612132, 23 Dec 2006, published as Impact of data sources on citation counts and rankings of LIS faculty: Web of science versus scopus and google scholar, in Journal of the American Society for Information Science and Technology, Vol. 58, No. 13, 2007, 2105-2125

Added 17 January 2007 Neuhaus, C. and Daniel, H.-D. (2006) Data sources for performing citation analysis: An overview, ETH E-Collection, June 30, 2006, Journal of Documentation, accepted for publication
Reports the limitations of Thomson Scientific's citation indexes and reviews the characteristics of the citation-enhanced databases Chemical Abstracts, Google Scholar and Scopus.

Added 8 March 2007 Bosman, J., van Mourik, I., Rasch, M., Sieverts, E. and Verhoeff, H. (2006) Scopus reviewed and compared, Igitur repository, Utrecht University, June 2006
The coverage and functionality of the citation database Scopus, including comparisons with Web of Science and Google Scholar

Wenzel, E. (2006) Google Scholar beta, ZDNet, May 2, 2006
Brief comparison of Google Scholar and Microsoft Live Academic Search

Added 23 November 2006 Jacsó, P. (2005) Comparison and analysis of the citedness scores in Web of Science and Google Scholar (pdf 10pp), Digital Libraries: Implementing Strategies and Sharing Experiences, Lecture Notes In Computer Science, 3815: 360-369, 2005, Proceedings of the 8th International Conference on Asian Digital Libraries, ICADL 2005, Bangkok, Thailand, December 12-15, 2005

Background

The financial imperative: correlating research access, impact and assessment

"Research impact translates into money: employment, salary, tenure money, as well as research-funding money: (1) RAE rank correlates with substantial top-sliced funding, (2) it also correlates highly (0.91) with citation counts, and (3) self-archiving increases citation counts by 50-250+%. Do you really think that any researcher who is *aware* of those three correlations is being rational if he doesn't self-archive?" Stevan Harnad

Added 28 May 2013 San Francisco Declaration on Research Assessment (DORA) (2013)
American Society for Cell Biology (ASCB), 17 May 2013
From DORA: There is a pressing need to improve the ways in which the output of scientific research is evaluated by funding agencies, academic institutions, and other parties. ... The Journal Impact Factor is frequently used as the primary parameter with which to compare the scientific output of individuals and institutions. The Journal Impact Factor, as calculated by Thomson Reuters, was originally created as a tool to help librarians identify journals to purchase, not as a measure of the scientific quality of research in an article. With that in mind, it is critical to understand that the Journal Impact Factor has a number of well-documented deficiencies as a tool for research assessment. These limitations include: A) citation distributions within journals are highly skewed; B) the properties of the Journal Impact Factor are field-specific: it is a composite of multiple, highly diverse article types, including primary research papers and reviews; C) Journal Impact Factors can be manipulated (or "gamed") by editorial policy; and D) data used to calculate the Journal Impact Factors are neither transparent nor openly available to the public. we make a number of recommendations for improving the way in which the quality of research output is evaluated. A number of themes run through these recommendations:

Added 4 March 2013 Ulf Kronman (2013)
Managing your assets in the publication economy
Confero: Essays on Education, Philosophy and Politics, 1-35, 17 Jan 2013
info:doi/10.3384/confero13v1130117
Abstract: The issue this article aims to address is the fact that publications may nowadays be used to assess impact and quality of research in ways academics may not be fully aware of. During recent years, scholarly publications have gained in importance, not primarily as the traditional vehicle for the dissemination of new scientific findings, but as a foundation for assessing the production and impact of organizations, research groups and individual researchers. This means that publications as artefacts per se are starting to play a new important role in the scientific community and that researchers need to be aware of how publication and citation counts are being used to assess their research and the outreach, impact and reputation of their mother organization. University rankings, for instance, often have some parameters based on the publishing of the ranked institution. This article is thus not about scientific writing as such; it focuses on what happens to your publication after the publishing has taken place and on aspects to take into account while planning the publishing of your article, report or book.

Added 18 August 2011 Spörrle, M. and Tumasjan, A. (2011)
Using Search Engine Count Estimates as Indicators of Academic Impact: A Web-based Replication of Haggbloom et al's (2002) Study
The Open Psychology Journal, 4, 12-18, 13 July 2011
DOI: 10.2174/1874350101104010012
Abstract: Using a complex set of quantitative and qualitative indicators of scientific importance, Haggbloom et al. compiled a ranking of the most eminent psychologists of the 20th century. The present study set out to replicate this rankordered list using simple search engine count estimates (SECEs) obtained from three popular internet search engines. In line with our expectations, our results revealed a small, but significant relationship between SECEs and the existing offline ranking when the query specified the scientists field of research (i.e., psychology). Our results imply that SECEs may be considered easy to apply indicators of a researchers impact.

Added 06 July 2011 Li, R. (2011)
Correlation of Impact Measures of Institutional Repositories and PBRF Ranking
ResearchArchive @ Victoria, 18 May 2011
Master's thesis. From the Abstract: This study examines the correlation of website impact factor of institutional repositories (IR) of all eight universities in New Zealand and the Performance Based Research Fund (PBRF) quality score. The research also studied the different web ranking tools and tried to find out whether these tools can be used to measure the quality of IR documents. The research used Yahoo Site Explorer to collect information of inlinks and also use other tools to collect the webpage ranking. The finding of this research are that there is small correlation between the IR website impact factor and PBRF quality score, and the page ranking is not a good tool to exam the quality of IR document as a whole.

Added 18 October 2010 Suber, P. (2010)
Thinking about prestige, quality, and open access
SPARC Open Access Newsletter, issue #125, September 2, 2008
Brief extracts. Here are a dozen thoughts or theses about prestige and OA. I start with the rough notion that if journal quality is real excellence, then journal prestige is reputed excellence. (1) Universities reward faculty who publish in high-prestige journals, and faculty are strongly motivated to do so. If universities wanted to create this incentive, they have succeeded. If journal prestige and journal quality can diverge, then universities and funders may be giving authors an incentive to aim only for prestige. If they wanted to create an incentive to put quality ahead of prestige, they haven't yet succeeded. (8) Universities tend to use journal prestige and impact as surrogates for quality. The excuses for doing so are getting thin.

Added 18 October 2010 Willinsky, J. (2010)
Open access and academic reputation
NISCAIR Online Periodicals Repository (NOPR), Annals of Library and Information Studies, 57 (3), Sep 2010, 296-302
Abstract: Open access aims to make knowledge freely available to those who would make use of it. High-profile open access journals, such as those published by PLoS (Public Library of Science), have been able to demonstrate the viability of this model for increasing an authors reach and reputation within scholarly communication through the use of such bibliographic tools as the Journal Impact Factor, conceived and developed by Eugene Garfield. This article considers the various approaches that authors, journals, and funding agencies are taking toward open access, as well as its effect on reputation for authors and, more widely, for journals and the research enterprise itself.

Added 6 September 2010 Li, J., Sanderson, M., Willett, P., Norris, M. and Oppenheim, C. (2010)
Ranking of Library and Information Science Researchers: Comparison of Data Sources for Correlating Citation Data and Expert Judgments
Journal of Informetrics, 16 Jun 2010
Open access provides scope for new citation-based metrics, but these would have to be tested and validated against current, preferred methods of assessment. This paper is not focussed on open access, but it shows how such testing and validation might be performed.
From the Abstract: This paper studies the correlations between peer review and citation indicators when evaluating research quality in library and information science (LIS). Forty two LIS experts provided judgments on a five-point scale of the quality of research published by 101 scholars; the median rankings resulting from these judgments were then correlated with h-, g- and H-index values computed using three different sources of citation data: Web of Science (WoS), Scopus and Google Scholar (GS).

Added 28 July 2008 Adler, R., Ewing, J. (Chair) and Taylor, P. (2008)
Citation Statistics (pdf 26pp)
Joint Committee on Quantitative Assessment of Research, International Mathematical Union, IMU-ICIAM-IMS, 6/11/2008

Harnad, S., Citation Statistics: International Mathematical Union Report, Open Access Archivangelism blog, June 15, 2008: "what all this valuable, valid cautionary discussion overlooks is not only the possibility but the empirically demonstrated fact that there exist metrics that are highly correlated with human expert rankings. It follows that to the degree that such metrics account for the same variance, they can substitute for the human rankings. The substitution is desirable, because expert rankings are extremely costly in terms of expert time and resources. Moreover, a metric that can be shown to be highly correlated with an already validated variable predictor variable (such as expert rankings) thereby itself becomes a validated predictor variable. And this is why the answer to the basic question of whether the RAE's decision to convert to metrics was a sound one is: Yes."
Bensman, S. J., IMU Critique of Citation Analysis, SIGMETRICS, 27 June 2008: "I checked the distribution of mathematics journals by impact factor in the 2007 SCI JCR. It was as I suspected. The range of impact factors was only from 0.108 to 2.739--extraordinarily low and tight--and the top journals on the impact factor had no review articles. This is suggestive of an extremely random citation pattern with no development of consensual paradigms. Therefore, math acts like a humanities in terms of its literature use, and citation analysis is probably not applicable to this discipline. If citation analysis is used, it has to be backed by other measures."
Singleton, A., Book Review, Learned Publishing, Vol. 21, No. 4, October 2008, 329-331: "For anyone experienced in these matters, or even in scholarly publishing or library and information science (LIS) generally, it consists mainly of statements of the fairly obvious - and a lot of repetition. ... Overall this is a curate's egg of a report. I think we deserve better. Since it comes in the name of three prestigious institutions, one might have expected the review to be more thorough and, perhaps, the text to be better edited, but for policymakers the examples and simplicity of statements will, I think, make it a useful document."

Added 28 July 2008 Taraborelli, D. (2008)
Soft peer review. Social software and distributed scientific evaluation (pdf 12pp)
In Proceedings of the 8th International Conference on the Design of Cooperative Systems (COOP 08), Carry-Le-Rouet, France, May 20-23, 2008
From the abstract: "I analyze the contribution that social bookmarking systems can provide to the problem of usage-based metrics for scientific evaluation. I suggest that collaboratively aggregated metadata may help fill the gap between traditional citation-based criteria and raw usage factors."

Added 13 January 2009 Pringle, J. (2008)
Trends in the use of ISI citation databases for evaluation
Learned Publishing, Vol. 21, No. 2, April 2008, 85-91
Abstract: "This paper explores the factors shaping the current uses of the ISI citation databases in evaluation both of journals and of individual scholars and their institutions. Given the intense focus on outcomes evaluation, in a context of increasing 'democratization' of metrics in today's digital world, it is easy to lose focus on the appropriate ways to use these resources, and misuse can result."

Added 11 February 2008 Armbruster, C. (2008)
Access, Usage and Citation Metrics: What Function for Digital Libraries and Repositories in Research Evaluation?
Social Science Research Network, February 05, 2008
From the abstract: "This systematic appraisal of the future role of digital libraries and repositories for metric research evaluation proceeds by investigating the practical inadequacies of current metric evaluation before defining the scope for libraries and repositories as new players. Services reviewed include: Leiden Ranking, Webometrics Ranking of World Universities, COUNTER, MESUR, Harzing POP, CiteSeer, Citebase, RePEc LogEc and CitEc, Scopus, Web of Science and Google Scholar."

Added 10 May 2007, Updated 17 July 2009 Harnad, S. (2007)
Open Access Scientometrics and the UK Research Assessment Exercise
ArXiv, Computer Science, cs.IR/0703131, 26 March 2007. Preprint of invited keynote address to 11th Annual Meeting of the International Society for Scientometrics and Informetrics, Madrid, 25-27 June 2007
also in ECS EPrints, 29 March 2007 http://eprints.ecs.soton.ac.uk/13804/
Latest version ECS EPrints, 27 Feb 2009 http://eprints.ecs.soton.ac.uk/17142/, in Scientometrics, 79 (1), 2009, 147-156, published online: 13 November 2008, http://dx.doi.org/10.1007/s11192-009-0409-z

Added 26 September 2005 Harnad, S. (2005)
Maximising the Return on UK's Public Investment in Research
Author eprint, September 14, 2005
Attempts to monetise 'lost' impact: "The online-age practice of self-archiving has been shown to increase citation impact by a dramatic 50-250%, but so far only 15% of researchers are doing it spontaneously. Citation impact is rewarded by universities (through promotions and salary increases) and by research-funders like RCUK (through grant funding and renewal) at a conservative estimate of £46 per citation. ... As a proportion of the RCUK's yearly £3.5bn research expenditure (yielding 130,000 articles x 5.6 = 761,600 citations), our conservative estimate would be 50% x 85% x £3.5.bn = £1.5bn worth of loss in potential research impact (323,680 potential citations lost)."
See also
Australia is not maximising the return on its research investment (ETD2005, Sydney) for the same estimate applied to the potential lost return ($425M) there.

Garfield, E. (1988)
Can Researchers Bank on Citation Analysis? (pdf 10pp)
Current Comments, No. 44, October 31, 1988
attached (pp 3-10)
Diamond, Jr., A. M. (1986)
What is a Citation Worth?
J. Hum. Resour., 21:200-15, 1986
Garfield comments on studies that attempt to quantify the reward system of science in terms of monetary returns to author salaries from article publication and citations, reprinting one of those studies

Citation analysis, indexes and impact factors

Added 25 June 2013 Björn Brembs, Katherine Button and Marcus Munafò (2013)
Deep impact: unintended consequences of journal rank
Front. Hum. Neurosci., 7:291, published online: 24 June 2013. Also in arXiv.org > cs > arXiv:1301.3748, v1, 16 Jan 2013 http://arxiv.org/abs/1301.3748
doi: 10.3389/fnhum.2013.00291
Abstract: Most researchers acknowledge an intrinsic hierarchy in the scholarly journals ("journal rank") that they submit their work to, and adjust not only their submission but also their reading strategies accordingly. On the other hand, much has been written about the negative effects of institutionalizing journal rank as an impact measure. So far, contributions to the debate concerning the limitations of journal rank as a scientific impact assessment tool have either lacked data, or relied on only a few studies. In this review, we present the most recent and pertinent data on the consequences of our current scholarly communication system with respect to various measures of scientific quality (such as utility/citations, methodological soundness, expert ratings or retractions). These data corroborate previous hypotheses: using journal rank as an assessment tool is bad scientific practice. Moreover, the data lead us to argue that any journal rank (not only the currently-favored Impact Factor) would have this negative impact. Therefore, we suggest that abandoning journals altogether, in favor of a library-based scholarly communication system, will ultimately be necessary. This new system will use modern information technology to vastly improve the filter, sort and discovery functions of the current journal system.

Added 17 June 2013 Mike Taylor (2013)
The Challenges of Measuring Social Impact Using Altmetrics
Research Trends, Issue 33, June 2013
Abstract: Altmetrics gives us novel ways of detecting the use and consumption of scholarly publishing beyond formal citation, and it is tempting to treat these measurements as proxies for social impact. However, altmetrics is still too shallow and too narrow, and needs to increase its scope and reach before it can make a significant contribution to computing relative values for social impact. Furthermore, in order to go beyond limited comparisons of like-for-like and to become generally useful, computation models must take into account different socio-economic characteristics and legal frameworks. However, much of the necessary work can be borrowed from other fields, and the author concludes that with certain extensions and added sophistication altmetrics will be a valuable element in calculating social reach and impact.

Added 13 May 2013 Mike Thelwall, Stefanie Haustein, Vincent Larivière, Cassidy R. Sugimoto (2013)
Do altmetrics work? Twitter and ten other social web services
Author preprint. PLoS ONE, 8(5): e64841, May 28, 2013 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0064841
doi:10.1371/journal.pone.0064841
Abstract: Altmetric measurements derived from the social web are increasingly advocated and used as early indicators of article impact and usefulness. Nevertheless, there is a lack of systematic scientific evidence that altmetrics are valid proxies of either impact or utility although a few case studies have reported medium correlations between specific altmetrics and citation rates for individual journals or fields. To fill this gap, this study compares 11 altmetrics with Web of Science citations for 76 to 208,739 PubMed articles with at least one altmetric mention in each case and up to 1,891 journals per metric. It also introduces a simple sign test to overcome biases caused by different citation and usage windows. Statistically significant associations were found between higher metric scores and higher citations for articles with positive altmetric scores in all cases with sufficient evidence (Twitter, Facebook wall posts, research highlights, blogs, mainstream media and forums) except perhaps for Google+ posts. Evidence was insufficient for LinkedIn, Pinterest, question and answer sites, and Reddit, and no conclusions should be drawn about articles with zero altmetric scores or the strength of any correlation between altmetrics and citations. Nevertheless, comparisons between citations and metric values for articles published at different times, even within the same year, can remove or reverse this association and so publishers and scientometricians should consider the effect of time when using altmetrics to rank articles. Finally, the coverage of all the altmetrics except for Twitter seems to be low and so it is not clear if they are prevalent enough to be useful in practice.

Added 13 May 2013 Stacy Konkiel and Dave Scherer (2013)
New Opportunities for Repositories in the Age of Altmetrics
Bulletin of the Association for Information Science and Technology, Vol. 39, No. 4, April/May 2013
University administrators are increasingly trying to find new ways to measure the impact of the scholarly output of their faculty, students and researchers through quantitative means. By reporting altmetrics (alternative metrics based on online activity) for their content, institutional repositories can add value to existing metrics and prove their relevance and importance in an age of growing cutbacks to library services. This article will discuss the metrics that repositories currently deliver and how altmetrics can supplement existing usage statistics to provide a broader interpretation of research-output impact for the benefit of authors, library-based publishers and repository managers, and university administrators alike.

Added 13 May 2013 Ross Mounce (2013)
Open Access and Altmetrics: Distinct but Complementary
Bulletin of the Association for Information Science and Technology, Vol. 39, No. 4, April/May 2013
Extract: Alongside (the) growth and preference for online journals, there has been a notable rise in the growth and popularity of a particular type of online journal - open access (OA) journals, which expressly allow anyone on the Internet to read them for free without paying. Such journals make it even easier for people to discover, access and re-use journal literature. With this change in the consumption pattern of journal content to online, new ideas such as altmetrics have arisen to help us better assess the influence and impact of online journal articles. This article considers the complementary relationship between OA journal publishing and altmetrics, scholarly impact measures derived from online activity, as a means of capturing and measuring some of the influence of online journal articles.

Added 13 May 2013 Greg Tananbaum (2013)
Article-Level Metrics: a SPARC Primer
SPARC, April 2013
From the Executive Summary: Article-Level Metrics (ALMs) can be employed in conjunction with existing metrics, which have traditionally focused on the long-term impact of a collection of articles (i.e., a journal) based on the number of citations generated. This primer is designed to give campus leaders and other interested parties an overview of what ALMs are, why they matter, how they complement established utilities, and how they can be used in the tenure and promotion process.

Added 9 April 2013 Petr Heneberg (2013)
Effects of Print Publication Lag in Dual Format Journals on Scientometric Indicators
PLoS ONE, 8(4): e59877, April 3, 2013
doi:10.1371/journal.pone.0059877
From the Abstract: Dual-format peer-reviewed journals (publishing both print and online editions of their content) adopted a broadly accepted strategy to shorten the publication lag: to publish the accepted manuscripts online ahead of their print editions, which may follow days, but also years later. Effects of this widespread habit on the immediacy index (average number of times an article is cited in the year it is published) calculation were never analyzed. Methodology/Principal Findings: Scopus database (which contains nearly up-to-date documents in press, but does not reveal citations by these documents until they are finalized) was searched for the journals with the highest total counts of articles in press, or highest counts of articles in press appearing online in 20102011. Number of citations received by the articles in press available online was found to be nearly equal to citations received within the year when the document was assigned to a journal issue. Thus, online publication of in press articles affects severely the calculation of immediacy index of their source titles, and disadvantages online-only and print-only journals when evaluating them according to the immediacy index and probably also according to the impact factor and similar measures. Conclusions/Significance: Caution should be taken when evaluating dual-format journals supporting long publication lag.

Added 28 March 2013 Ehsan Mohammadi, Mike Thelwall (2013)
Assessing non-standard article impact using F1000 labels
Scientometrics, published online 20 March 2013
DOI: 10.1007/s11192-013-0993-9
Abstract: Faculty of 1000 (F1000) is a post-publishing peer review web site where experts evaluate and rate biomedical publications. F1000 reviewers also assign labels to each paper from a standard list or article types. This research examines the relationship between article types, citation counts and F1000 article factors (FFa). For this purpose, a random sample of F1000 medical articles from the years 2007 and 2008 were studied. In seven out of the nine cases, there were no significant differences between the article types in terms of citation counts and FFa scores. Nevertheless, citation counts and FFa scores were significantly different for two article types: New finding and Changes clinical practice: FFa scores value the appropriateness of medical research for clinical practice and New finding articles are more highly cited. It seems that highlighting key features of medical articles alongside ratings by Faculty members of F1000 could help to reveal the hidden value of some medical papers.

Added 28 March 2013 Ludo Waltman, Rodrigo Costas (2013)
F1000 recommendations as a new data source for research evaluation: A comparison with citations
arXiv.org > cs > arXiv:1303.3875, 15 March 2013
Abstract: F1000 is a post-publication peer review service for biological and medical research. F1000 aims to recommend important publications in the biomedical literature, and from this perspective F1000 could be an interesting tool for research evaluation. By linking the complete database of F1000 recommendations to the Web of Science bibliographic database, we are able to make a comprehensive comparison between F1000 recommendations and citations. We find that about 2% of the publications in the biomedical literature receive at least one F1000 recommendation. Recommended publications on average receive 1.30 recommendations, and over 90% of the recommendations are given within half a year after a publication has appeared. There turns out to be a clear correlation between F1000 recommendations and citations. However, the correlation is relatively weak, at least weaker than the correlation between journal impact and citations. More research is needed to identify the main reasons for differences between recommendations and citations in assessing the impact of publications.

Added 4 March 2013 Adriano Tort, Ze Targino, and Olavo Amaral (2012)
Rising Publication Delays Inflate Journal Impact Factors
PLoS ONE, 7(12): e53374, 31 Dec 2012
info:doi/10.1371/journal.pone.0053374
From the Abstract: We analyze 61 neuroscience journals and show that delays between online and print publication of articles increased steadily over the last decade. Importantly, such a practice varies widely among journals, as some of them have no delays, while for others this period is longer than a year. Using a modified impact factor based on online rather than print publication dates, we demonstrate that online-to-print delays can artificially raise a journals impact factor, and that this inflation is greater for longer publication lags. We also show that correcting the effect of publication delay on impact factors changes journal rankings based on this metric. We thus suggest that indexing of articles in citation databases and calculation of citation metrics should be based on the date of an articles online appearance, rather than on that of its publication in print.

Added 4 March 2013 Emilio Lopez-Cozar, Nicolas Robinson-Garcia, and Daniel Torres-Salinas (2012)
Manipulating Google Scholar Citations and Google Scholar Metrics: simple, easy and tempting
arXiv.org > cs > arXiv:1212.0638, 04 Dec 2012
From the Abstract: The launch of Google Scholar Citations and Google Scholar Metrics may provoke a revolution in the research evaluation field as it places within every researchers reach tools that allow bibliometric measuring. In order to alert the research community over how easily one can manipulate the data and bibliometric indicators offered by Google's products we present an experiment in which we manipulate the Google Citations profiles of a research group through the creation of false documents that cite their documents, and consequently, the journals in which they have published modifying their H index.

Added 13 May 2013 Xuemei Li and Mike Thelwall (2012)
F1000, Mendeley and Traditional Bibliometric Indicators
In 17th International Conference on Science and Technology Indicators (STI), Montreal, 5-8 September 2012
Abstract: This article compares the Faculty of 1000 (F1000) quality filtering results and Mendeley usage data with traditional bibliometric indicators, using a sample of 1397 Genomics and Genetics articles published in 2008 selected by F1000 Faculty Members (FMs). Both Mendeley user counts and F1000 article factors (FFas) correlate significantly with citation counts and associated Journal Impact Factors. However, the correlations for Mendeley user counts are much larger than those for FFas. It may be that F1000 is good at disclosing the merit of an article from an expert practitioner point of view while Mendeley user counts may be more closely related to traditional citation impact. Articles that attract exceptionally many citations are generally disorder or disease related, while those with extremely high social bookmark user counts are mainly historical or introductory.

Added 4 December 2012 Daniel Acuna, Stefano Allesina, and Konrad Kording (2012)
Future impact: Predicting scientific success
Nature, 489 (7415), 201-2, 13 September 2012
info:doi/10.1038/489201a
Presents a formula to estimate the future h-index of life scientists. The h-index and similar metrics can capture only past accomplishments, not future achievements. Here we attempt to predict the future h-index of scientists on the basis of features found in most CVs.

Added 4 December 2012 Jasleen Kaur, Diep Thi Hoang, Xiaoling Sun, Lino Possamai, Mohsen JafariAsbagh, Snehal Patil, Filippo Menczer (2012)
Scholarometer: A Social Framework for Analyzing Impact across Disciplines
PLoS ONE, 7 (9), 12 September 2012
info:doi/10.1371/journal.pone.0043235
From the Abstract: We describe a system called Scholarometer, which provides a service to scholars by computing citation-based impact measures. This creates an incentive for users to provide disciplinary annotations of authors, which in turn can be used to compute disciplinary metrics. We first present the system architecture and several heuristics to deal with noisy bibliographic and annotation data. We report on data sharing and interactive visualization services enabled by Scholarometer. Usage statistics, illustrating the data collected and shared through the framework, suggest that the proposed crowdsourcing approach can be successful. Secondly, we illustrate how the disciplinary bibliometric indicators elicited by Scholarometer allow us to implement for the first time a universal impact measure proposed in the literature. Our evaluation suggests that this metric provides an effective means for comparing scholarly impact across disciplinary boundaries.

Added 16 August 2012 Daniel Torres-Salinas, Nicolas Robinson-Garcia, and Emilio Lopez-Cozar (2012)
Towards a Book Publishers Citation Reports. First approach using the Book Citation Index
Hacia un ranking bibliométrico de editoriales científicas de libros. Primera aproximación utilizando el Book Citation Index
arXiv.org > cs > arXiv:1207.7067, 29 Jul 2012, Grupo Evaluación de la Ciencia y la Comunicación Científica (EC3) Working Papers 7. In Revista española de Documentación Científica, Vol 35, No 4 (2012) http://redc.revistas.csic.es/index.php/redc/article/view/766
doi:10.3989/redc.2012.4.1010
Abstract: The absence of books and book chapters in the Web of Science Citation Indexes (SCI, SSCI and A&HCI) has always been considered an important flaw but the Thomson Reuters 'Book Citation Index' database was finally available in October of 2010 indexing 29,618 books and 379,082 book chapters. The Book Citation Index opens a new window of opportunities for analyzing these fields from a bibliometric point of view. The main objective of this article is to analyze different impact indicators referred to the scientific publishers included in the Book Citation Index for the Social Sciences and Humanities fields during 2006-2011. This way we construct what we have called the 'Book Publishers Citation Reports'. For this, we present a total of 19 rankings according to the different disciplines in Humanities & Arts and Social Sciences & Law with six indicators for scientific publishers

Added 16 August 2012 Joseph Bernstein and Chancellor Gray (2012)
Content Factor: A Measure of a Journal's Contribution to Knowledge
PLoS ONE, 7 (7), 23 Jul 2012
info:doi/10.1371/journal.pone.0041554
From the Abstract: We propose a metric, Content Factor, and examine its performance among leading medical and orthopaedic surgery journals. To remedy Impact Factor's emphasis on recent citations, Content Factor considers the total number of citations, regardless of the year in which the cited paper was published. To correct for Impact Factor's emphasis on efficiency, no denominator is employed. Content Factor is thus the total number of citations in a given year to all of the papers previously published in the journal. We found that Content Factor and Impact Factor are poorly correlated. We further surveyed 75 experienced orthopaedic authors and measured their perceptions of the importance of various orthopaedic surgery journals. The correlation between the importance score and the Impact Factor was only 0.08; the correlation between the importance score and Content Factor was 0.56.

Added 12 February 2012 Paul Wouters and Rodrigo Costas (2012)
Users, narcissism and control - tracking the impact of scholarly publications in the 21st century
SURFfoundation, February 2012
From the Executive summary: This report explores the explosion of tracking tools that have accompanied the surge of web based information instruments. The report therefore advises to start a concerted research programme in the dynamics, properties, and potential use of new web based metrics which relates these new measures to the already established indicators of publication impact. Its goal would be to contribute to the development of more useful tools for the scientific and scholarly community. This programme should monitor at least the following tools: F1000, Microsoft Academic Research, Total-Impact, PlosONE altmetrics, and Google Scholar. The programme should moreover develop the following key research themes: concepts of new web metrics and altmetrics; standardisation of tools and data; and the use and normalisation of the new metrics.

Added 12 February 2012 Cynthia Lokker, R. Brian Haynes, Rong Chu, K. Ann McKibbon, Nancy L. Wilczynski, and Stephen D. Walter (2012)
How well are journal and clinical article characteristics associated with the journal impact factor? a retrospective cohort study
Journal of the Medical Library Association, 100 (1), 28-33, January 2012. Via PubMed Central
From the Abstract: A retrospective cohort study determined the ability of clinical article and journal characteristics, including appraisal measures collected at the time of publication, to predict subsequent JIFs. Four of the 10 measures were significant in the regression model: number of authors, number of databases indexing the journal, proportion of articles passing methods criteria, and mean clinical newsworthiness scores. For the clinical literature, measures of scientific quality and clinical newsworthiness available at the time of publication can predict JIFs with 60% accuracy.

Added 12 February 2012 Xuemei Li, Mike Thelwall, and Dean Giustini (2011)
Validating online reference managers for scholarly impact measurement
Scientometrics, 21 December 2011
info:doi/10.1007/s11192-011-0580-x
(Subscription access required. Online preview.) Abstract: This paper investigates whether CiteULike and Mendeley are useful for measuring scholarly influence, using a sample of 1,613 papers published in Nature and Science in 2007. Traditional citation counts from the Web of Science (WoS) were used as benchmarks to compare with the number of users who bookmarked the articles in one of the two free online reference manager sites. Statistically significant correlations were found between the user counts and the corresponding WoS citation counts, suggesting that this type of influence is related in some way to traditional citation-based scholarly impact but the number of users of these systems seems to be still too small for them to challenge traditional citation indexes.

Added 12 February 2012 William J. Sutherland, David Goulson, Simon G. Potts, Lynn V. Dicks (2011)
Quantifying the Impact and Relevance of Scientific Research
PLoS ONE, 6 (11), e27537, November 16, 2011
info:doi/10.1371/journal.pone.0027537
Abstract: Qualitative and quantitative methods are being developed to measure the impacts of research on society, but they suffer from serious drawbacks associated with linking a piece of research to its subsequent impacts. We have developed a method to derive impact scores for individual research publications according to their contribution to answering questions of quantified importance to end users of research. To demonstrate the approach, here we evaluate the impacts of research into means of conserving wild bee populations in the UK. For published papers, there is a weak positive correlation between our impact score and the impact factor of the journal. The process identifies publications that provide high quality evidence relating to issues of strong concern. It can also be used to set future research agendas.

Added 12 February 2012 Perry Evans and Michael Krauthammer (2011)
Exploring the Use of Social Media to Measure Journal Article Impact
American Medical Informatics Association (AMIA) Annual Symposium Proceedings Archive, 374-81, 22 October 2011. Via PubMed Central
From the Abstract: Using Wikipedia as a proxy for other social media, we explore the correlation between inclusion of a journal article in Wikipedia, and article impact as measured by citation count. We start by cataloging features of PubMed articles cited in Wikipedia. We find that Wikipedia pages referencing the most journal articles are about disorders and diseases, while the most referenced articles in Wikipedia are about genomics. We note that journal articles in Wikipedia have significantly higher citation counts than an equivalent random article subset. We also observe that articles are included in Wikipedia soon after publication. Our data suggest that social media may represent a largely untapped post-publication review resource for assessing paper impact.

Added 06 July 2011 Merceur, F., Le Gall, M. and Salaun, A. (2011)
Bibliometrics: a new feature for institutional repositories
Archimer, Ifremer's institutional repository, May 2011. In 14th Biennal EURASLIC Meeting, Lyon, 17-20 May, 2011
From the Abstract: In addition to its promotion and conservation objectives, Archimer, Ifremers institutional repository, offers a wide range of bibliometric tools described in this document.

Added 18 October 2010 Herb, U. (2010)
OpenAccess Statistics: Alternative Impact Measures for Open Access documents? An examination how to generate interoperable usage information from distributed Open Access services
E-LIS, 25 Sep 2010. In: L'information scientifique et technique dans l'univers numérique. Mesures et usages. L'association des professionnels de l'information et de la documentation, ADBS, pp. 165-178
From the abstract: This contribution shows that most common methods to assess the impact of scientific publications often discriminate Open Access publications and by that reduce the attractiveness of Open Access for scientists. Assuming that the motivation to use Open Access publishing services (e.g. a journal or a repository) would increase if these services would convey some sort of reputation or impact to the scientists, alternative models of impact are discussed. Prevailing research results indicate that alternative metrics based on usage information of electronic documents are suitable to complement or to relativize citation-based indicators. Furthermore an insight into the project OpenAccess-Statistics OA-S is given. OA-S implemented an infrastructure to collect document-related usage information from distributed Open Access Repositories in an aggregator service in order to generate interoperable document access information according to three standards (COUNTER, LogEc and IFABC).

Added 6 September 2010 Herb, U., Kranz, E., Leidinger, T. and Mittelsdorf, B. (2010)
How to assess the impact of an electronic document? And what does impact mean anyway?: Reliable usage statistics in heterogeneous repository communities
E-LIS, 10 Jun 2010. In OCLC Systems & Services, Vol. 26, No. 2, 2010, 133-145
From the Abstract: Purpose - Usually the impact of research and researchers is quantified by using citation data: either by journal-centered citation data as in the case of the journal impact factor (JIF) or by author-centered citation data as in the case of the Hirsch- or h-index. This paper aims to discuss a range of impact measures, especially usage-based metrics, and to report the results of two surveys. Originality/value - This paper delineates current discussions about citation-based and usage-based metrics. Based on the results of the surveys, it depicts which functionalities could enhance repositories, what features are required by scientists and information professionals, and whether usage-based services are considered valuable. These results also outline some elements of future repository research.

Added 6 September 2010 Repanovici, A. (2010)
Measuring the visibility of the University's scientific production using GoogleScholar, "Publish or Perish" software and Scientometrics
76th IFLA General Conference and Assembly, Gothenburg, Sweden, 07 Jun 2010
In Performance Measurement and Metrics, Vol. 12, No. 2, 2011. From the Abstract: The first Romanian institutional repository was implemented at Transilvania University of Brasov. As part of the undertaken research, the visibility and the impact of the university's scientific production was measured using the scientific methods of scientometry, as a fundamental instrument for determining the international value of an university as well as for the statistical evaluation of scientific research results. The results showed that an open access institutional repository would significantly add to the visibility of the university's scientific production. In this article we define the scientific production and productivity and present the main indicators for the measurement of the scientific activity. Google Scholar was used as a scientometric database which can be consulted free of charge on the Internet and which indexes academic papers from institutional repositories, identifying also the referenced citations. The free Publish or Perish software can be used as an analysis instrument for the impact of the research, by analysing the citations through the h-index. We present the methodology and the results of an exploratory study made at the Transilvania University of Brasov regarding the h-index of the academic staff.

Added 9 June 2010 Neff, B. and Olden, J. (2010)
Not So Fast: Inflation in Impact Factors Contributes to Apparent Improvements in Journal Quality
BioScience, 60 (6), 455-9, June 2010
From the Abstract: Here we propose that impact factors may be subject to inflation analogous to changes in monetary prices in economics. The possibility of inflation came to light as a result of the observation that papers published today tend to cite more papers than those published a decade ago. We analyzed citation data from 75,312 papers from 70 ecological journals published during 1998-2007. We found that papers published in 2007 cited an average of seven more papers than those published a decade earlier. This increase accounts for about 80% of the observed impact factor inflation rate of 0.23. In examining the 70 journals we found that nearly 50% showed increases in their impact factors, but at rates lower than the background inflation rate. Therefore, although those journals appear to be increasing in quality as measured by the impact factor, they are actually failing to keep pace with inflation.

Added 6 September 2010 Repanovici, A. (2010)
Measuring the visibility of the universities scientific production using scientometric methods
6th WSEAS/IASME International Conference on Educational Technologies (EDUTE '10), 03 May 2010
Abstract: Paper presents scientometry as a science and a fundamental instrument for determining the international value of an university as well as for the statistical evaluation of scientific research results. The impact of the research measurable through scientometric indicators is analyzed. Promoting the scientific production of universities through institutional digital repositories deals with the concept of scientific production of the university and the development of scientific research in information society. These concepts are approached through the prism of marketing methods and techniques. The digital repository is analyzed as a PRODUCT, destined for promoting, archieving and preserving scientific production. Find out more about the author and the paper here.
The record and abstract page for the paper does not currently link to the full text.

Added 6 September 2010 Wardle, D. (2010)
Do Faculty of 1000 (F1000) ratings of ecological publications serve as reasonable predictors of their future impact?
Ideas in Ecology and Evolution, 3, 2010, 11-15
Commentary article.
From the Abstract: There is an increasing demand for an effective means of post-publication evaluation of ecological work that avoids pitfalls associated with using the impact factor of the journal in which the work was published. One approach that has been gaining momentum is the Faculty of 1000 (hereafter F1000) evaluation procedure, in which panel members identify what they believe to be the most important recent publications they have read. Here I focused on 1530 publications from 7 major ecological journals that appeared in 2005, and compared the F1000 rating of each publication with the frequency with which it was subsequently cited. ... Possible reasons for the F1000 process failing to identify high impact publications may include uneven coverage by F1000 of different ecological topics, cronyism, and geographical bias favoring North American publications. As long as the F1000 process cannot identify those publications that subsequently have the greatest impact, it cannot be reliably used as a means of post-publication evaluation of the ecological literature.

Added 9 June 2010 Bornmann, L. and Daniel, H.-D. (2010)
The citation speed index: A useful bibliometric indicator to add to the h index
Authors' server, undated but notice posted to Sigmetrics listserv 26 March 2010, in Journal of Informetrics, accepted for publication
This topic would appear to be a natural complement to OA citation effects, but the paper does not mention any.

Added 9 Mar 2010 Bar-Ilan, J. (2009)
A Closer Look at the Sources of Informetric Research
CYBERmetrics, 13 (1), 23 Dec 2009
From the introduction: The Web has existed for twenty years only, yet the large majority of the data sources for informetric research are available through the Web. ISI's Web of Science was launched in 1997 ... In November 2004 two additional major citation databases appeared on the Web: Elsevier's Scopus and Google Scholar ... and there are easily accessible and often open-source software tools that enable to collect and analyze large quantities of data even on a personal computer. It has become easy to conduct "desktop or poor-man's bibiliometrics". The data for informetric research have never been perfect, but now that informetric analysis can be conducted with much greater ease than before, it is even more important to understand the limitations and problems of data sources and methods and to assess the validity of the results. In the following sections I discuss some limitations of the existing sources.

Added 9 Mar 2010 Ball, K. (2009)
The Indexing of Scholarly Open Access Business Journals
Electronic Journal of Academic and Special Librarianship, 10 (3), Winter 2009
"this study focusses on the business and management field and assess the extent to which scholarly open access journals in this discipline are currently being indexed by both commercial and non-commercial indexing services. Of the commercial indexing services, Ebscos Business Source Complete covers by far the largest number of open access journals. For business researchers working in an academic environment, Business Source Complete, with its more sophisticated searching and browsing capabilities and deeper historical coverage, is probably the best one-stop option for retrieving scholarly materials from both the subscription-based and OA literature. However, from a simple quantity perspective, OA business journals are being most extensively indexed by OA indexing services, in particular, Google Scholar and Open J-Gate."

Added 9 Mar 2010 Moed, H. (2009)
Measuring contextual citation impact of scientific journals
ArXiv, arXiv:0911.2632v1 [cs.DL], 13 Nov 2009. Also in Journal of Informetrics (to appear)
About journal impact, and not directly about open access. From the abstract: "This paper explores a new indicator of journal citation impact, denoted as source normalized impact per paper (SNIP). It measures a journal's contextual citation impact, taking into account characteristics of its properly defined subject field, especially the frequency at which authors cite other papers in their reference lists, the rapidity of maturing of citation impact, and the extent to which a database used for the assessment covers the field's literature. It aims to allow direct comparison of sources in different subject fields."

Added 15 Oct 2009 Armbruster, C. (2009)
Whose Metrics? On Building Citation, Usage and Access Metrics as Information Service for Scholars
SSRN Social Science Research Network, 31 Aug 2009
Services mentioned: Journal impact factor, journal usage factor, GoPubMed, SSRN CiteReader, RePEc LogEc, RePEc CitEc, SPIRES, Harzing POP, Webometrics, ISI Web of Knowledge, Scopus, Google Scholar, Citebase, CiteSeer X, CERIF

Added 9 Mar 2010 Patterson, M. (2009)
PLoS Journals measuring impact where it matters
PLoS blog, 2009-07-13
On why PLoS is will no longer highlight the journal impact factor. Instead it will present a range of metrics focussed on the published paper, including individual citation counts from various sources, blog and bookmark counts, links and searches, as illustrated by Peter Binfield in the PLoS one community blog (March 31, 2009): "rather than updating the PLoS Journal sites with the new numbers, weve decided to stop promoting journal impact factors on our sites all together. Its time to move on, and focus efforts on more sophisticated, flexible and meaningful measures."

Added 9 Mar 2010 Canos Cerda, J. H., Campos, M. L. and Nieto, E. M. (2009)
What's Wrong with Citation Counts?
D-Lib Magazine, Vol. 15 No. 3/4, March/April 2009
From the abstract: "We argue that a new approach based on the collection of citation data at the time the papers are created can overcome current limitations, and we propose a new framework in which the research community is the owner of a Global Citation Registry characterized by high quality citation data handled automatically."

Added 26 February 2009 Cross, J. (2009)
Impact factors - the basics
The E-Resources Management Handbook (2006 - present), UKSG, this chapter published online: 03 February 2009

Added 10 November 2008 Leydesdorff, L. (2008)
How are new citation-based journal indicators adding to the bibliometric toolbox?
Author preprint, undated, (announced 31 Oct 2008), in Journal of the American Society for Information Science and Technology, Vol. 60, No. 7, 2009, 1327-1336, published online: 2 Feb 2009 http://dx.doi.org/10.1002/asi.21024
From the abstract: "The launching of Scopus and Google Scholar, and methodological developments in social-network analysis have made many more indicators for evaluating journals available than the traditional impact factor, cited half-life, and immediacy index of the ISI. In this study, these new indicators are compared with one another and with the older ones."

Added 9 June 2010 Final Impact: What Factors Really Matter? (VIDEO) (2008)
Scholarly Communication Program, Columbia University, October 30, 2008
Panelists: Marian Hollingsworth, Thomson Reuters; Jevin West, Eigenfactor.org; and Johan Bollen, Los Alamos National Laboratory

Added 10 November 2008 Radicchi, F., Fortunato, S. and Castellano, C. (2008)
Universality of citation distributions: towards an objective measure of scientific impact
arXiv.org, arXiv:0806.0974v2 [physics.soc-ph], 5 Jun 2008 (v1), last revised 27 Oct 2008
in Proceedings of the National Academy of Sciences of The United States of America, 105 (45): 17268-17272, Nov. 11 2008

Added 10 November 2008 Banks, M. A. and Dellavalle, R. (2008)
Emerging Alternatives to the Impact Factor
E-LIS, 05 September 2008, also in OCLC Systems & Services, 24(3)

Added 10 November 2008 Brumback, R. A. (2008)
Worshiping false idols: the impact factor dilemma
J. Child Neurol., Vol. 23, No. 4, April 2008, 365-367
"the opacity in Thomson Scientific's refusal to reveal the details of their calculations only serves to increase suspicion about possible data manipulations. ... Now would seem to be the appropriate time for the academic community to demand valid metrics to assess published scientific material"

Added 26 May 2008 Althouse, B. M., West, J. D., Bergstrom, T. C. and Bergstrom, C. T. (2008)
Differences in Impact Factor Across Fields and Over Time
eScholarship Repository, California Digital library, Department of Economics, University of California Santa Barbara, Departmental Working Papers, paper 2008-4-23, April 23, 2008. In Journal of the American Society for Information Science and Technology, Vol. 60, No. 1, 27-34, published online: 21 Aug 2008

Added 11 February 2008 Kosmopoulos, C. et Pumain, D. (2007)
Citation, Citation, Citation: Bibliometrics, the web and the Social Sciences and Humanities
Cybergeo, Science et Toile, article 411, mis en ligne le 17 decembre 2007, modifie le 18 janvier 2008
From the abstract: "The paper reviews the main (bibliometric) data bases and indicators in use. It demonstrates that these instruments give a biased information about the scientific output of research in Social Sciences and Humanities."

Added 28 July 2008 Rossner, M., Van Epps, H. and Hill, E. (2007)
Show me the data (editorial)
The Journal of Cell Biology, Vol. 179, No. 6, 1091-1092, published online December 17, 2007
"Just as scientists would not accept the findings in a scientific paper without seeing the primary data, so should they not rely on Thomson Scientific's impact factor, which is based on hidden data. As more publication and citation data become available to the public through services like PubMed, PubMed Central, and Google Scholar®, we hope that people will begin to develop their own metrics for assessing scientific quality rather than rely on an ill-defined and manifestly unscientific number."

Added 17 January 2007 Meho, L. I. (2006)
The Rise and Rise of Citation Analysis
Author eprint, dLIST, 31 December 2006, Physics World, January 2007
"Provides a historical background of citation analysis, impact factor, new citation data sources (e.g., Google Scholar, Scopus, NASA's Astrophysics Data System Abstract Service, MathSciNet, ScienceDirect, SciFinder Scholar, Scitation/SPIN, and SPIRES-HEP), as well as h-index, g-index, and a-index."

Added 3 May 2007 Ewing, J. (2006)
Measuring Journals
Notices of the AMS, Vol. 53, No. 9, October 2006, 1049-1053
"in many respects usage statistics are even more flawed than the impact factor, and once again, the essential problem is that there are no explicit principles governing their interpretation. ... while usage statistics are only slightly useful, their misuse can be enormously damaging."

Added 8 March 2007 Garfield, E. (2006)
Commentary: Fifty years of citation indexing
International Journal of Epidemiology, 2006 35(5):1127-1128, published online September 19, 2006

Added 28 February 2006 Noruzi, A. (2006)
The Web Impact Factor: a critical review (pdf, 10pp)
E-LIS, February 9, 2006, in The Electronic Library, 24 (2006)
"Web Impact Factor (WIF) is a quantitative tool for evaluating and ranking web sites ... search engines provide similar possibilities for the investigation of links between web sites/pages to those provided by the academic journals citation databases from the Institute of Scientific Information (ISI). But the content of the Web is not of the same nature and quality as the databases maintained by the ISI."

Added 28 February 2006 Bollen, J., Rodriguez, M. A. and Van de Sompel, H. (2006)
Journal Status (pdf, 16pp)
Arxiv, 9 January 2006
"By merely counting the amount of citations and disregarding the prestige of the citing journals, the ISI IF is a metric of popularity, not of prestige. We demonstrate how a weighted version of the popular PageRank algorithm can be used to obtain a metric that reflects prestige. ... Furthermore, we introduce the Y-factor which is a simple combination of both the ISI IF and the weighted PageRank, and find that the resulting journal rankings correspond well to a general understanding of journal status."

Added 28 February 2006 Dong, P., Loh, M. and Mondry, A. (2005)
The "impact factor" revisited
Biomedical Digital Libraries, December 2005
This is a review, so the findings are not new, but this is perhaps the first such paper to reflect on the effect of free and online availability on journal impact factors, among other IF-related issues.

Added 30 December 2005 Hardy, R., Oppenheim, C., Brody, T. and Hitchcock, S. (2005)
Open Access Citation Information (.doc, 105pp)
Author eprint, November 11, 2005, JISC Committee for the Information Environment (JCIE) Scholarly Communication Group, September 2005
Describes a proposal to increase the exposure of open access materials and their references to indexing services, and to motivate new services by reducing setup costs.

Added 8 March 2007 Perkel, J. M. (2005)
The Future of Citation Analysis
The Scientist, Vol. 19, No. 20, October 24, 2005
"The challenge is to track a work's impact when published in nontraditional forms"

Publishers promote impact factors of OA journals
BioMed Central "Open access journals get impressive impact factors" 23 June 2005
Public Library of Science "The first impact factor for PLoS Biology - 13.9" 27 June 2005
See also this discussion of these announcements on SPARC Open Access Forum, prompted by Elsevier's response from Tony McSean, followed by David Goodman, Charles Bailey, (both 8 July) and Matthew Cockerill (10 July), or see this summary of the discussion: "BMC's Impact Factors: Elsevier's Take and Reactions to It", Digital Koans (Charles Bailey's Weblog), 11 July 2005, including Peter Suber's conclusion: "It's important to distinguish the citation impact of an individual article from a journal impact factor. The BMC-Elsevier debate is about the latter. But OA is more likely to rise and fall according to the former."

Baudoin, L., Haeffner-Cavaillon, N., Pinhas, N., Mouchet, S. and Kordon, C. (2004)
Bibliometric indicators: realities, myth and prospective (abstract only, full paper in French)
Med Sci (Paris), 20 (10):909-15, October 2004

Added 26 September 2005 Shin E. J. (2003)
Do Impact Factors change with a change of medium? A comparison of Impact Factors when publication is by paper and through parallel publishing (abstract only)
Journal of Information Science, 29 (6): 527-533, 2003
"it is found that Impact Factors of (journals from the period) 2000 and 2001 were significantly higher than those of 1994 and 1995 in the journals published by parallel publishing (combination journals—simultaneous publication of paper and electronic journals). In particular, the Impact Factors of the combination journals increased after the journals transformed their available media from paper journals to combination ones."

Borgman, C. L. and Furner, J. (2002)
Scholarly Communication and Bibliometrics, author preprint (pdf 45pp)
Author eprint, in Annual Review of Information Science and Technology, Vol. 36, edited by B. Cronin, 2002

Wouters, P. (1999)
The Citation Culture (pdf 290pp)
PhD Thesis, University of Amsterdam, 1999

Open access

Swan, A. (2007)
Open Access and the Progress of Science
American Scientist, April-June 2007
Swan justified open access in support of her 'progress' article in a list discussion. See blogged extracts from that discussion.

Swan, A. (2006)
Open Access: Why should we have it?
presented at "Zichtbaar onderzoek. Kan Open Archives daarbij helpen?" / Visible research. Can OAI help? Organised by AWI (Flemish Ministry for Economy, Enterprise, Science, Innovation and Foreign Trade) and VOWB (Flemish Organisation of Scientific Research Libraries), May 2006