Scandinavian Working Papers in Economics
Working Paper Series,
Sveriges Riksbank (Central Bank of Sweden)
No 168: Is Firm Interdependence within Industries Important for Portfolio Credit Risk?
Kenneth Carling (), Lars Rönnegård () and Kasper Roszbach ()
Additional contact information
Kenneth Carling: IFAU, Uppsala and Dalarna University, Postal: SE-781 88 Borlänge, Sweden
Lars Rönnegård: Dalarna University, Postal: SE-781 88 Borlänge, Sweden
Kasper Roszbach: Research Department, Central Bank of Sweden, Postal: Sveriges Riksbank, SE-103 37 Stockholm, Sweden
Abstract: A drawback of available portfolio credit risk models is that they fail to allow for default risk dependency across loans other than through common risk factors. Thereby, thesemodels ignore that close ties can exist between companies due to legal, financial and business relations. In this paper, we integrate the insights from theoretical models of default correlation into a commonly used model of default and portfolio credit risk by allowing for dependency between firm default risk through both common factors and industry specific errors in a duration model. An application using pooled data from two Swedish banks’ business loan portfolios over the period 1996-2000 shows that estimates of individual default risk are little affected by including industry specific errors. However, accounting for these industry effects increases VaR estimates by 50-200 percent. A traditional model with only systematic factors, although able to fit the broad trends in credit losses, cannot match these fluctuations because it fails to capture credit losses in bad times, when banks are typically hit by large unexpected credit losses. The model we propose manages to follow both the trend in credit losses and produce industry driven, time-varying, fluctuations in losses around that trend. Consequently, this model will better aid banks and regulators in determining the appropriate size of economic capital requirements. Capital buffers derived from our model will be larger for periods with large ”aggregate” disturbances and smaller in better times, and avoid both overcapitalization in good times and undercapitalization in bad times.
Keywords: value-at-risk; credit risk; portfolio credit risk; duration model; default correlation; industry dependency; cluster errors
JEL-codes: C34; C35; D61; D81; G21
36 pages, August 1, 2004
Full text files
WP_168.pdf
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