This paper gives a simple introduction to portfolio credit risk models of the factor model type. In factor models, the dependence between the individual defaults is driven by a small number of systematic factors. When conditioning on the realisation of these factors the defaults become...

Prior research uses the basic one-period European call-option pricing model to compute default measures for individual firms and concludes that both the size and book-to-market effects are related to default risk. For example, small firms earn higher return than big firms only if they have...