Credit Ratings, Credit Default Swaps and Credit Correlation

Abstract

This thesis looks at the statistical interaction of credit ratings and Credit Default Swap (CDS) spreads. Both have been implicated as major contributors to the financial crises of 2007-present. The body of work contained herein looks to further our understanding of their relationship and in doing so, I make three empirical contributions to the fields of credit risk and financial economics. Firstly, in Chapter 2, I uncover a striking empirical artifact contained within CDS correlation dynamics. Namely, that there is a well-defined credit rating structure embedded in them. Although much of the extant literature treats credit derivatives and equity as contingent claims on the same underlying firm value, by contrast, no rating-based structure exists in equity correlations. In Chapter 3, I demonstrate that rating-based correlation dynamics in CDS markets are not fully consistent with the traditional framework of financial economics in which a security’s price merely reflects its fundamental value. I show that the trading behaviour of market participants in relation to CDS indices, the constituents of which are based on the discrete and somewhat arbitrary labeling of issuers as either investment-grade or high-yield, drives a distortion in single-name CDS co-movement. My results can be interpreted as the first evidence of a significant departure from traditional views of market efficiency in a $30 trillion segment of global derivatives markets. Finally, in Chapter 4, I go on to explore the complete time-series and cross-sectional interaction of the credit rating process on CDS spreads. In doing so, I identify that prior to the crisis, credit rating agencies played a much greater role in the price discovery process of corporate credit risk. As such, there has been a significant loss of information in credit ratings. This result can be explained via a loss of confidence in rating agencies due to a spill-over effect of reputational damage from their role in the collapse of the $3tn structured credit derivatives market. The use of ex post hyper-inflated AAA ratings on CDOs and RMBS, and the subsequent fall-out from doing so, has altered how credit market participants react to the information contained in corporate credit ratings. These results are particularly relevant in light of impending regulatory reform under the Dodd-Frank act of 2010.