Stressing correlations and volatilities — A consistent modeling approach

We propose a new approach to the definition of stress scenarios for volatilities and correlations. Correlations and volatilities depend on a common market factor, which is the key to stressing them in a consistent and intuitive way. Our approach is based on a new asset price model where correlations and volatilities depend on the current state of the market, which captures market-wide movements in equity-prices. For sample portfolios we compare correlations and volatilities in a normal market and under stress and explore consequences for value-at-risk.We compare our modeling approach with multivariate GARCH models. For all data analyzed our model performs well in capturing the dynamics of volatilities and correlations under stress.

► We determine stressed correlations and value-at-risk based on new asset price model.
► This study confirms estimates and fulfills requirements of Basel III.
► Volatilities and correlations dynamically depend on common state of the market factor.