Are the Fama-French Factors Proxying Default Risk?

In this paper we investigate the contention that the Fama-French (1993) model's ability to explain cross-sectional variation in equity returns occurs because the Fama-French factors, SMB and HML, are proxying for default risk. To assess the default risk hypothesis, we augment the CAPM and the Fama-French model with a default factor and run system regressions of the default enhanced models using the GMM approach. Our key findings are that: 1) default risk is not priced in equity returns; and, 2) the Fama-French factors are not proxying for default risk. Although our findings suggest that SMB and HML are not proxying for default risk, our analysis indicates that the Fama-French factors are capturing some form of priced risk. However, what type of risk the Fama-French factors are capturing remains an open question.