Risk managing tail-risk seekers: VaR and expected shortfall vs S-shaped utility
File(s)
Author(s)
Armstrong, John
Brigo, Damiano
Type
Journal Article
Abstract
We consider market players with tail-risk-seeking behaviour modelled by S-shaped utility, as introduced by Kahneman and Tversky. We argue that risk measures such as value at risk (VaR) and expected shortfall (ES) are ineffective in constraining such players, as such measures cannot reduce the traders expected S-shaped utilities. Indeed, when designing payoffs aiming to maximize utility under a VaR or ES risk limit, the players will attain the same supremum of expected utility with or without VaR or ES limits. By contrast, we show that risk management constraints based on a second more conventional concave utility function can reduce the maximum S-shaped utility that can be achieved by the investor. Indeed, product designs leading to progressively larger S-shaped utilities will lead to progressively lower expected constraining conventional utilities, violating the related risk limit. These results hold in a variety of market models, including the Black Scholes options model, and are particularly relevant for risk managers given the historical role of VaR and the endorsement of ES by the Basel committee in 2012–2013.
Date Issued
2019-04
Date Acceptance
2019-01-19
Citation
Journal of Banking & Finance, 2019, 101, pp.122-135
ISSN
0378-4266
Publisher
Elsevier BV
Start Page
122
End Page
135
Journal / Book Title
Journal of Banking & Finance
Volume
101
Copyright Statement
© 2019 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Subjects
0102 Applied Mathematics
1502 Banking, Finance and Investment
Finance
Publication Status
Published
Date Publish Online
2019-01-29