Credit Rating Migration Risk and Business Cycles

Abstract

Basel III seeks to improve the financial sector's resilience to stress scenarios which calls for a reassessment of banks' credit risk models and, particularly, of their dependence on business cycles. This paper advocates a Mixture of Markov Chains (MMC) model to account for stochastic business cycle effects in credit rating migration risk. The MMC approach is more efficient and provides superior out-of-sample credit rating migration risk predictions at long horizons than a naïve approach that conditions deterministically on the business cycle phase. Banks using the MMC estimator would counter-cyclically increase capital by 6% during economic expansion and free up to 17% capital for lending during downturns relative to the naïve estimator. Thus, the MMC estimator is well aligned with the Basel III macroprudential initiative to dampen procyclicality by reducing the recession-versus-expansion gap in capital buffers.