Table III shows that, as the credit quality of the reference entity declines, the implied
risk-free rate rises. A possible explanation for this is that there is counterparty default risk
in a CDS (that is, there is some possibility that the seller of the CDS will default). Hull
and White (2001) provide an analytic approximation for the impact of counterparty
default risk on CDS spreads. Using their formula with reasonable estimates of the
parameters we were able to provide only a partial explanation of the differences between
the results for rating categories in Table III. We conclude that the results may be
influenced by other factors such as differences in the liquidities of the bonds issued by
reference entities in different rating categories.