The Importance of Estimation Uncertainty in a Multi-Rating Class Loan Portfolio

This article seeks to make an assessment of estimation uncertainty in a multi-rating class loan portfolio. Relationships are established between estimation uncertainty and parameters such as probability of default, intra- and inter-rating class correlation, degree of inhomogeneity, number of rating classes used, number of debtors and number of historical periods used for parameter estimations. In addition, by using an exemplary portfolio based on Moody's ratings, it becomes clear that estimation uncertainty does indeed have an effect on interest rates.