Technical paper/Credit risk
Correlation evidence
Like ratings, default correlation is an area of fierce industry debate. But any fundamental, long-terminvestor searching for fair value in credit correlation will want to understand what the historical dataactually says.
Market-implied ratings
There has been much debate over the respective merits of credit ratings and market-based indicators. Ludovic Breger, Lisa Goldberg and Oren Cheyette present a new approach that tries to incorporate the benefits of both approaches. Starting with agency…
Correlation evidence
Like ratings, default correlation is an area of fierce industry debate. But any fundamental, long-term investor searching for fair value in credit correlation will want to understand what the historical data actually says. Here, Arnaud de Servigny and…
The road to partition
Applying the ensemble approach developed in these pages last month, Kevin Thompson and Roland Ordovas calculate risk contributions and show how to measure higher-order default dependence using the method of partitions. The results provide tools allowing…
Enhancing CreditRisk+
Of the various analytical approaches to credit portfolio modelling, CreditRisk+ has become the most popular due to its tractability. However, the model suffers from the restrictive assumption of sector independence. Moreover, the recursion relation for…
Credit ensembles
Kevin Thompson and Roland Ordovas address the question of how individual counterparties contribute to the total credit risk of a portfolio. They provide an analytic method, new to credit modelling, to estimate all joint default statistics conditional…
Contributions to credit risk
Optimisation of credit portfolios requires that risk contributions be quantified. However, there has been disagreement over which of three popular tail risk measures should be used. Here, Alexandre Kurth and Dirk Tasche offer a way forward, showing how…
Random tranches
How should economic or regulatory capital be allocated to tranches of securitisations? The standard Basel conditional dependence calculations are complicated in this case by non-linearity effects and complex deal dependence. Here, Michael Gordy and David…
Coarse-grained CDOs
While analytical models of credit portfolio risk using conditional independence have been one of the most promising areas of recent research, they often involve granularity assumptions that are violated in CDO reference portfolios. Here, Michael Pykhtin…
Loan portfolio value
Using a conditional independence framework, Oldrich Vasicek derives a useful limiting form for the portfolio loss distribution with a single systematic factor. He then derives a risk-neutral distribution suitable for traded portfolios, and shows how…
Unsystematic credit risk
Although Basel has shifted its treatment of unsystematic credit risk from the first, capital rules pillar (where it was called the ‘granularity adjustment’) to the second, supervisory pillar of the forthcoming Accord, this issue is of great practical…
Avoiding pro-cyclicality
David Cosandey and Urs Wolf argue that, for small to medium-sized enterprises, Basel II is pro-cyclical because of a double-counting of the risks. They present two main directions for possible capital rules that would circumvent the pro-cyclicality…
Copula vulnerability
Counterparty credit risk
Calculating portfolio loss
For credit portfolios, analytical methods work best for tail risk, while Monte Carlo is used to model expected loss. However, products such as CDOs require a model for the entire distribution. Sandro Merino and Mark Nyfeler meet the challenge by…
The maturity effect on credit risk capital
In a mark-to-market approach to credit risk capital, ratings or spread volatility has the effect of making longer-maturity loans more capital-intensive. This is incorporated in the current Basel II proposals via a maturity adjustment factor. Arguing that…
Pro-cyclicality in the new Basel Accord
Could Basel II worsen recessions? By backtesting the proposed capital rules to the last recession, D. Wilson Ervin and Tom Wilde argue that the increased risk sensitivity of loan portfolio regulatory capital in the new Accord could have unwelcome…
Probing granularity
The granularity adjustment, which adjusts risk weightings for credit portfolio diversification, is one of Basel II’s key modelling assumptions. Here, Tom Wilde uncovers a weakness in this assumption arising from the differences in the underlying credit…
Weighting for Risk
Basel has recognised that collateral and seniority give banks an advantage when an obligor defaults. Here, Jon Frye argues that the proposal may encourage banks to lend on the collateral – a practice that could threaten their own survival – and proposes…