This paper provides an overview on classical and new methods for testing time series properties of migration matrices. It is well known that due to cyclical behaviour of the economy transition matrices for many credit portfolios cannot be considered to be constant through time. Further,...

Lending specialization on certain industry sectors can have opposing effects on monitoring (including screening) abilities and on the sectoral concentration risk of a credit portfolio. In this paper, we examine in the first part if monitoring abilities of German cooperative banks and savings...

Die Bewertung der Ausfallwahrscheinlichkeiten von Ratingklassen, basierend auf historischen Daten, ist mit Schätzunsicherheit verbunden. Zur Bewertung dieser Unsicherheit werden in der Literatur Konfidenzintervalle diskutiert. Diesen liegen allerdings Annahmen bezüglich der Abhängigkeiten...

Within the Internal Ratings-Based (IRB) approach of Basel II it is assumed that idiosyncratic risk has been fully diversi?ed away. The impact of undiversi?ed idiosyncratic risk on portfolio Value-at-Risk can be quanti?ed via a granularity adjustment (GA). We provide an analytic formula for the...

In 2005 the Internal Ratings Based (IRB) approach of `Basel II' was enhanced by a `treatment of double default effects' to account for credit risk mitigation techniques such as ordinary guarantees or credit derivatives. This paper reveals several severe problems of this approach and presents a...

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...