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Market crashes and value-at-risk models

Market crashes and value-at-risk models
Market crashes and value-at-risk models
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
5-26
Persand, G.
c1b50342-bfb4-4a40-9f03-b352ba2076f2
Brooks, C.
91d99e42-37f5-4b2b-87a2-c3df0c926b5f
Persand, G.
c1b50342-bfb4-4a40-9f03-b352ba2076f2
Brooks, C.
91d99e42-37f5-4b2b-87a2-c3df0c926b5f

Persand, G. and Brooks, C. (2000) Market crashes and value-at-risk models. Journal of Risk, 2 (4), 5-26.

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: 35870
URI: http://eprints.soton.ac.uk/id/eprint/35870
ISSN: 1465-1211
PURE UUID: e40abe37-f5f3-467a-a321-9ce1f0321afb

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Date deposited: 26 Jul 2006
Last modified: 11 Dec 2021 15:30

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Contributors

Author: G. Persand
Author: C. Brooks

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