Basel II Second Pillar: An analytical VaR with contagion and sectorial risks

by Michele Bonollo of Banco Popolare & Università di Padova,
Paola Mosconi of Iason Ltd, and
Fabio Mercurio of Bloomberg & Iason Ltd

January 29, 2009

Abstract: This paper deals with the effects of concentration (single name and sectoral) and contagion risk on credit portfolios. Results are obtained for the value at risk of the portfolio loss distribution, in the analytical framework originally developed by Vasicek in 1991 [1]. VAR is expressed as a sum of terms: the first contribution represents the value at risk of a hypothetical single-factor homogeneous portfolio, the remaining terms are corrections due to contagion, imperfect granularity and multiple industry-geographic sectors. A detailed numerical analysis is also presented.

JEL Classification: C63, G11, G38.

Keywords: Basel II, second pillar, credit VaR, analytical formula, contagion, sectorial risk.

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