Determinants of systematic volatility of corporate bonds

This paper examines the association between betas of corporate bonds and their duration, coupon, maturity, agency rating, and other attributes. The data consist of monthly returns of 386 bonds, from January 1973 to June 1976. Betas are generated with the S&P 500 Index, a corporate bond index, and a U.S. bond index. The chief conclusions are the following: 1) Systematic volatility and its determinants differ according to the index; 2) betas formed with an equity or corporate bond index are negatively related to rating; and 3) duration is superior to coupon and term in explaining beta.