the web's biggest credit risk modeling resource.

Credit Jobs

Home Glossary Links FAQ / About Site Guide Search


Submit Your Paper

In Rememberance: World Trade Center (WTC)

doi> search: A or B

Export citation to:
- Text (plain)
- BibTeX

Discriminatory Power: An obsolete validation criterion?

by Manuel Lingo of the Vienna University of Economics and Business Administration, and
Gerhard Winkler of Oesterreichische Nationalbank

February 2008

Abstract: In this paper we analyse two common measures of discriminatory power - the Accuracy Ratio and the Area Under the Receiver Operator Characteristic - in a probabilistic framework. Under the assumption of a random default event, we verify that the measures will be portfolio dependent as discovered by Hamerle et al. (2003) and furthermore stochastic as indicated by Blochwitz et al. (2005). As an extension of these two papers we first study how the structure of a portfolio influences the measures. Furthermore we demonstrate that the measures contain information about a rating system's calibration quality. To this end a testing procedure is developed that also allows for a comparison of the measures across different portfolios. Our analysis leads to the final conclusion that high granularity and good calibration quality are sufficient to maximize attainable discriminatory power and are thus the sole criteria to be considered in any validation exercise.

JEL Classification: G20, C49.

Keywords: Credit Risk, Validation, Discriminatory Power, Calibration Quality, ROC, CAP.

Published in: Journal of Risk Model Validation, Vol. 2, No. 1, (Spring 2008), pp. 1-27.

Books Referenced in this paper:  (what is this?)

Download paper (675K PDF) 43 pages