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Value-at-risk and market crashes

Value-at-risk and market crashes
Value-at-risk and market crashes
Many popular techniques for determining a securities firm's value-at-risk are based upon the calculation of the historical volatility of returns to the assets that comprise the portfolio and of the correlations between them. One such approach is the JP Morgan RiskMetrics methodology using Markowitz portfolio theory. An implicit assumption underlying this methodology is that the volatilities and correlations are constant throughout the sample period and, in particular, that they are not systematically related to one another. However, it has been suggested in a number of studies that the correlation between markets increases when the individual volatilities are high. This paper demonstrates that this type of relationship between correlation and volatility can lead to a downward bias in the estimated value-at-risk, and proposes a number of pragmatic approaches that risk managers might adopt for dealing with this issue.
1465-1211
63-66
Brooks, Chris
2be5f663-66b8-43d2-903c-6f800e6e2385
Persand, Gita
d60c4b3f-fd3b-4b0a-892f-3c4eb992f15d
Brooks, Chris
2be5f663-66b8-43d2-903c-6f800e6e2385
Persand, Gita
d60c4b3f-fd3b-4b0a-892f-3c4eb992f15d

Brooks, Chris and Persand, Gita (2000) Value-at-risk and market crashes. Journal of Risk, 2 (4), 63-66.

Record type: Article

Abstract

Many popular techniques for determining a securities firm's value-at-risk are based upon the calculation of the historical volatility of returns to the assets that comprise the portfolio and of the correlations between them. One such approach is the JP Morgan RiskMetrics methodology using Markowitz portfolio theory. An implicit assumption underlying this methodology is that the volatilities and correlations are constant throughout the sample period and, in particular, that they are not systematically related to one another. However, it has been suggested in a number of studies that the correlation between markets increases when the individual volatilities are high. This paper demonstrates that this type of relationship between correlation and volatility can lead to a downward bias in the estimated value-at-risk, and proposes a number of pragmatic approaches that risk managers might adopt for dealing with this issue.

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Published date: 2000

Identifiers

Local EPrints ID: 35869
URI: http://eprints.soton.ac.uk/id/eprint/35869
ISSN: 1465-1211
PURE UUID: b048facf-16fc-48bb-a597-0a396633d14f

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Date deposited: 28 Jul 2006
Last modified: 23 Jul 2020 16:34

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