In this study Jarrow Turnbull (1995) Model, which is a reduced form approach for credit risk models, is employed to estimate the default intensity of US corporate bonds conditionally based on a fixed recovery rate. The estimations are performed with respect to the ratings of the bonds and the results were consistent with the ratings. US Treasury Bills are also used to since zero coupon default free prices, modeled by Svensson (1994) are necessary for pricing the default risky coupon bonds.

Credit risk measurement and management has great importance in credit market. Credit derivative products are the major hedging instruments in this market and credit default swap contracts (CDSs) are the most common type of these instruments. As observed in credit crunch (credit crisis) that has started from the United States and expanded all over the world, especially crisis of Iceland, CDS premiums (prices) are better indicative of credit risk than credit ratings. Therefore, CDSs are important indicators for credit risk of an obligor and thus these products should be understood by market participants well enough. In this thesis, initially, advanced credit risk models firsts, the structural (firm value) models, Merton Model and Black-Cox constant barrier model, and the intensity-based (reduced-form) models, Jarrow-Turnbull and Cox models, are studied. For each credit risk model studied, survival probabilities are calculated. After explaining the basic structure of a single name CDS contract, by the help of the general pricing formula of CDS that result from the equality of in and out cash flows of these contracts, CDS price for each structural models (Merton model and Black-Cox constant barrier model) and CDS price for general type of intensity based models are obtained. Before the conclusion, default intensities are obtained from the distribution functions of default under two basic structural models / Merton and Black-Cox constant barrier. Finally, we conclude our work with some inferences and proposals.

本文之信用風險模型屬於簡約模型(Reduced Form Model)之範疇，以COX過程解釋違約過程，解釋為何企業會發生連帶倒閉的現象。在考慮信用風險後，各期所產生之現金流量變得具不確定性，因此在計算現金流量之現值時，折現因子就必須考慮信用風險溢酬，本文選用信用風險模型中的一大分支-約簡模型，將信用風險量化(包含系統風險及非系統風險)，進而估計出信用價差期間結構；就如同無風險利率期間結構對固定收益商品之重要性，在估計出公司之信用價差期間結構後，即可針對該公司發行之各種商品進行評價分析。本文並以花旗所羅門美邦控股公司為例進行實證，利用公司債理論價格與市價之誤差平方和，求解違約過程之參數估計值及信用價差期間結構；接著，針對花旗所羅門美邦控股公司所發行之連動債券〝TRAGETS〞，進行評價分析並比較考慮信用風險與否是否有助於理論價格與市價之配適。