In this chapter we explore the traditional and prevalent approach to credit risk assessment—the credit
rating system. Most rating systems are based on both quantitative and qualitative evaluations. The
final decision is based on many different attributes, but usually it is not calculated using a formal
model that would show how to weight all these attributes in a normative way. In essence, the systems
are based on general considerations and on experience, and not on mathematical modeling. They
cannot therefore be regarded as precise, and they also clearly rely on the judgement of the ratings
evaluators.