We show that the saddle-point approximation method to quantify the impact of undiversified idiosyncratic risk in a credit portfolio is inappropriate in the presence of double default effects. Specifically, we prove that there does not exist an equivalent formula to the granularity adjustment,...

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

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...

An enduring puzzle is why credit rating agencies (CRAs) use a few categories to describe credit qualities lying in a continuum, even when ratings coarseness reduces welfare. We model a cheap-talk game in which a CRA assigns positive weights to the divergent goals of issuing firms and investors....

Advocates for internal model-based capital regulation argue that this approach will reduce costs and remove distortions that are created by rules-based capital regulations. These claims are examined using a Merton-style model of deposit insurance. Analysis shows that internal model-based capital...

The recent switch from the incurred credit loss model to the expected credit loss model is an important change to bank financial reporting systems around the world. The expected credit loss model requires banks to monitor their borrowers closely for more timely recognition of loan losses. We...

We model the evolution of stylised bank loan portfolios to assess the impact of IFRS 9 and US GAAP expected loss model (ECL) on the cyclicality of loan write-off losses, loan loss provisions (LLPs) and capital ratios of banks, relative to the incurred loss model of IAS 39. We focus on the...

In the wake of the recent financial crisis, many governments extended public guarantees to banks. We take advantage of a natural experiment, in which long-standing public guarantees were removed for a set of German banks following a lawsuit, to identify the real effects of these guarantees on...