Are Credit Spreads and Interest Rates co-integrated? Empirical Analysis in the USD Corporate Bond Market

Structural models for pricing risky debt imply a negative relationship betweeninterest rates and credit spreads. In contrast, credit default swap pricing modelsassume independence between credit risk and the term structure of interest rates.So far, empirical studies have focused on first differences of time series and confirmedthe negative relation implied by structural models based on Merton (1974).Nevertheless, the co-integration analysis of Morris, Neal and Rolph (1998) finds apositive long-run relation between the credit spread and the risk free interest ratewhich is not supported by the theoretical literature.This paper analyses the relationship between different forms of credit spreads andinterest rates using the co-integration approach developed by Engle and Granger(1987). Our study is based on weekly USD corporate bond index data which is controlledfor rating ranging from 1994 to 2006. We confirm the negative relation betweencredit spreads and interest rates with high statistical significance. Furthermore,we find that the S&P 500 stock index and the spread between the swap curve andthe Treasury yield curve can be considered as additional factors explaining the creditspread.