The Informational Content of Bond Ratings
Louis H. Ederington, Jess B. Yawitz, Brian E. Roberts
NBER Working Paper No. 1323
This paper explores the risk structure of interest rates. More specifically, we ask whether yields on industrial and commercial bonds indicate that market participants base their evaluations of a bond issue's default risk on agency ratings or on publically available financial statistics. Using a non-linear least squares procedure, we relate the yield to maturity to Moody's rating, Standard & Poor's rating, and accounting measures of credit worthiness such as coverage and leverage. We find that market yields are significantly correlated with both the ratings and with a set of readily available financial accounting statistics. These results indicate (1) that market participants base their evaluations of an issue's credit worthiness on more than the agencies' ratings and (2) that the ratings bring some information to the market above and beyond that contained in the set of accounting variables. In addition, our results suggest that the market views Moody's and S&P's ratings as equally reliable measures of risk. Although the accounting measures also affect yields on new or recently reviewed issues, our analysis suggests that the market may pay more attention to the accounting measures and less to the ratings if the rating has not been reviewed recently.
Published: JFR, Vol. 10, no. 3 (1987): 211-226.