Since 1999 an increase in magnitude and volatility of the yield spread between corporate and government bonds is not only observable in the US bond market, but also in the German bond market. This so called quality or credit spread is defined as the inter-market yield difference between seasoned non-government and seasoned risk-free government bonds, which are assumed to be identical in all respects except for credit quality.

Much academic work interprets this spread as a measure of market’s perception of the credit risk implied with corporate bonds. Since highly rated corporates have little probability of default, the credit spread seems too large to be explained solely by default risk premium. Additionally some studies reveal a low explanatory power of the default risk for the level as well as for the changes in the US corporate yield spread. In recent literature the yield spread is regarded as a measure of a comprehensive risk premium to compensate investors for a number of risks associated with corporate bonds. Furthermore a possible influence of demand and supply factors triggering the observed recent variations in the spread is discussed. Published empirical work has concentrated though almost uniquely on the US bond market, only very few studies are available for the German market.