Credit risk is an important issue in many finance areas, such as the determination of cost of capital, the valuation of corporate bonds and pricing of credit derivatives. Credit risk has also been a cause and consequence of the current financial crisis. Thus, methods for measuring credit risk,...

Rating downgrades are known to make subsequent downgrades more likely. We analyze the impact of this 'downward momentum' on credit portfolio risk. Using S&P ratings from 1996 to 2005, we estimate a transition matrix that is insensitive to and a second matrix that is sensitive to previous...