Recent calibration studies suggest that a sizable component of corporate bond spreads cannot be explained by credit risk (Jones, Mason and Rosenfeld, 1984; Elton, Gruber, Agrawal and Mann, 2001; Eom, Helwege and Huang, 2004), especially for high-rung investment-grade bonds at the short maturity (Huang and Huang, 2003). While existing empirical studies link this nondefault component of bond spreads to bond liquidity (Longstaff, Mithal and Neis, 2005; Ericsson, Reneby and Wang, 2006; Nashikkar and Subrahmanyam, 2006), most of the evidence suggests that only speculative-grade bonds have a significant exposure to the liquidity risk factors (see Chen et al. (2005), Chacko (2005), de Jong and Driessen (2004), and Downing, Underwood and Xing (2005), among others).