Assessing the protection provided by misclassification-based disclosure limitation methods for survey microdata.

Shlomo, Natalie and Skinner, Chris (2010) Assessing the protection provided by misclassification-based disclosure limitation methods for survey microdata. The Annals of Applied Statistics, Vol. 4 (No. 3).

Abstract

Government statistical agencies often apply statistical disclosure limitation techniques to survey microdata to protect the confidentiality of respondents.

There is a need for valid and practical ways to assess
the protection provided. This paper develops some simple methods for disclosure limitation techniques which perturb the values of categorical identifying variables. The methods are applied in numerical experiments based upon census data from the United Kingdom which are subject to
two perturbation techniques: data swapping (random and targeted) and the post randomisation method. Some simplifying approximations to the measure of risk are found to work well in capturing the impacts of these techniques.

These approximations provide simple extensions of existing risk assessment methods based upon Poisson log-linear models. A numerical experiment is also undertaken to assess the impact of multivariate misclassification with an increasing number of identifying variables.

It is found that the misclassification dominates the usual
monotone increasing relationship between this number and risk so that the risk eventually declines, implying less sensitivity of risk to choice of identifying variables. The methods developed in this paper may also be used to obtain more realistic assessments of risk which take account
of the kinds of measurement and other non-sampling errors commonly arising in surveys.

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