Jens Hilscher and Mungo Wilson Propose a New Measure of Systematic Credit Risk
Nov. 21, 2016
The study shows that a straightforward and easy-to-implement and interpret measure of default probability contains significantly more information about future default and failure than S&P corporate credit ratings. Jens Hilscher and Mungo Wilson propose a new measure of systematic credit risk, the tendency for firms to default in bad times, just when the marginal investor is least able to absorb losses. They provide a theoretical justification for the measure, which they call failure beta, and show that ratings contain information about systematic default risk, which is also reflected in credit default swap (CDS) spreads.
This paper investigates the information in corporate credit ratings. If ratings are to be informative indicators of credit risk, they must reflect what a risk-averse investor cares about: both raw default probability and systematic risk. We find that ratings are relatively inaccurate measures of raw default probability—they are dominated as predictors of failure by a simple model based on publicly available financial information. However, ratings do contain relevant information since they are related to a measure of exposure to common (and undiversifiable) variation in default probability (“failure beta”). Systematic risk is shown to be related to joint default probabilities in the context of the Merton [Merton RC (1974) On the pricing of corporate debt: The risk structure of interest rates. J. Finance 29(2):449–470] model. Empirically, it is related to credit default swap spreads and risk premia. Given the multidimensional nature of credit risk, it is not possible for one measure to capture all the relevant information.
Hilscher, J. & M. Wilson. 2016. "Credit Ratings and Credit Risk: Is One Measure Enough?" Management Science.
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