Credit Risk
§Corporate bonds are subject to potential default. Therefore, the promised yield is the maximum possible yield to maturity of the bond, not necessarily the actual yield to maturity. 
§To compensate investors for the possibility of bankruptcy, a corporate bond must offer a default premium, a differential between the promised yield and the expected yield to maturity.
§The default premium depends on :
othe probability of default
othe likely loss in the event of default.