This is the first study that uses Merton's (1974) option pricing model to compute default measures for individual firms and assess the effect of default risk on equity returns. The size effect is a default effect, and this is also largely true for the bookto-market (BM) effect. Both exist only in segments of the market with high default risk. Default risk is systematic risk. The Fama-French (FF) factors SMB and HML contain some default-related information, but this is not the main reason that the FF model can explain the cross section of equity returns.A FIRM DEFAULTS WHEN IT FAILS to service its debt obligations. Therefore, default risk induces lenders to require from borrowers a spread over the risk-free rate of interest. This spread is an increasing function of the probability of default of the individual firm.Although considerable research effort has been put toward modeling default risk for the purpose of valuing corporate debt and derivative products written on it, little attention has been paid to the effects of default risk on equity returns. 1 The effect that default risk may have on equity returns is not obvious, since equity holders are the residual claimants on a firm's cash f lows and there is no promised nominal return in equities.Previous studies that examine the effect of default risk on equities focus on the ability of the default spread to explain or predict returns. The default spread is usually defined as the yield or return differential between long-term BAA corporate bonds and long-term AAA or U.S. Treasury bonds.2 However, * Vassalou is at Columbia University and Xing is at Rice University. ton (1995, 1997), Jarrow and Turnbull (1995), Longstaff and Schwartz (1995), Zhou (1997), Lando (1998), andDuffee (1999), among others.2 For instance, many studies have shown that the yield spread between BAA and AAA corporate bond spread can predict expected returns in stocks and bonds. Such studies include those of Fama and Schwert (1977), Keim and Stambaugh (1986), Campbell (1987), and Fama and French (1989,
832The Journal of Finance as Elton et al. (2001) show, much of the information in the default spread is unrelated to default risk. In fact, as much as 85 percent of the spread can be explained as reward for bearing systematic risk, unrelated to default. Furthermore, differential taxes seem to have a more important inf luence on spreads than expected loss from default. These results lead us to conclude that, independent of whether the default spread can explain, predict, or otherwise relate to equity returns, such a relation cannot be attributed to the effects that default risk may have on equities. In other words, we still know very little about how default risk affects equity returns.The purpose of this paper is to address precisely this question. Instead of relying on information about default obtained from the bonds market, we estimate default likelihood indicators (DLI) for individual firms using equity data. These DLI are nonlinear functions of the default probabilities of the in...