VaR and time‐varying volatility: a comparative study of three international portfolios

Abstract

PurposeThis study aims to evaluate the market risk exposure of three international equity portfolios using value‐at‐risk (VaR). This risk metric calculates the worst case loss for a business in the course of its daily transactions. To ensure that the calculated VaR reflects emerging risk characteristics, this paper introduces an approach that incorporates time‐varying volatility.Design/methodology/approachThis study uses the GARCH technique to calculate the volatility metric with which VaR estimates are obtained. The out‐of‐sample performance of the VaRs is then assessed by comparing them to the actual market risk losses in that period.FindingsEmpirical results show that regardless of market conditions, the VaR calculated with this (GARCH) approach is more robust and more reliable than the traditional methods. Pursuant to the banking regulation on market risk capital stipulated by the Basel Committee on Banking Supervision, the out‐of‐sample VaRs are at least equal to actual daily market risk losses at the 99 percent confidence level.Practical implicationsThe key goal of banking regulation is to ensure that financial firms have sufficient capital for the types of risks they take. Determining the right amount of capital requires these firms to first estimate their worst case loss, which is the value‐at‐risk. The approach to the calculation of VaR introduced in this paper enhances the accuracy in the measurement of market risk capital for financial institutions.Originality/valueThis paper recognizes that for VaR to fully account for market risk losses, the risk metric must be correctly measured. The unparalleled approach in this paper of incorporating time‐varying volatility in VaR calculations offers banking institutions a more reliable means of determining their capital adequacy.