The Role of Default Correlation in Valuing Credit Dependant Securities

In this thesis, I imply a forward-looking systematic factor from CDO market spreads; I show that this factor is a measure of CDO market's expectation of future default correlation, and I empirically show that it is positively related to bond credit spreads. From this, I infer that corporate bond credit spreads are positively related to expected default correlation. The forward-looking factor stems from a CDO valuation model that I propose. The model assumes default can be characterized as a random event that occurs with an uncertain hazard rate that is mixture-Weibull distributed. Calibrating the model to CDO market spreads implies the model parameters. Using two and three mixing densities and data spanning January 2004 to February 2008, I show that the model calibrates to both the North American and European investment grade CDOs with negligible error. The factor I imply from the CDO market quotes is the standard deviation of the implied hazard rate density. I then show that the standard deviation of the implied hazard rate density increases as default correlation increases. This is done by characterizing firms' defaults with stochastic hazard rates that are defined by jump-diffusion processes that are correlated only through the Weiner processes, only through systematic jumps, or both. I use the models to generate CDO model spreads that are used to imply mixture-Weibull hazard rate densities. In addition, I provide evidence that the implied hazard rate density standard deviation has time variation that is independent to that of other common systematic factors. Lastly, I show that bond credit spreads are positively correlated with the standard deviation of the implied hazard rate density, and I conclude that credit spreads are positively related to expected default correlation. I provide evidence that firms' credit spreads are decreasing in firm diversity; that credit spread sensitivity to default correlation is decreasing in firm equity option implied volatility and decreasing in firm diversity; and that the variation in high credit quality bond spreads is predominantly explained by systematic factors whereas the variation in low credit quality bond spreads is explained by systematic and idiosyncratic factors.Ph