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Measuring portfolio credit risk correctly: why parameter uncertainty matters

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  • Nikola Tarashev

Abstract

Why should risk management systems account for parameter uncertainty? In order to answer this question, this paper lets an investor in a credit portfolio face non-diversifiable estimation-driven uncertainty about two parameters: probability of default and asset-return correlation. Bayesian inference reveals that - for realistic assumptions about the portfolio's credit quality and the data underlying parameter estimates - this uncertainty substantially increases the tail risk perceived by the investor. Since incorporating parameter uncertainty in a measure of tail risk is computationally demanding, the paper also derives and analyzes a closed-form approximation to such a measure.

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  • Nikola Tarashev, 2009. "Measuring portfolio credit risk correctly: why parameter uncertainty matters," BIS Working Papers 280, Bank for International Settlements.
  • Handle: RePEc:bis:biswps:280
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    References listed on IDEAS

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    2. Liao, Hsien-Hsing & Chen, Tsung-Kang & Lu, Chia-Wu, 2009. "Bank credit risk and structural credit models: Agency and information asymmetry perspectives," Journal of Banking & Finance, Elsevier, vol. 33(8), pages 1520-1530, August.
    3. Lütkebohmert, Eva & Gordy, Michael B., 2007. "Granularity adjustment for Basel II," Discussion Paper Series 2: Banking and Financial Studies 2007,01, Deutsche Bundesbank.
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    6. Forte, Santiago & Peña, Juan Ignacio, 2009. "Credit spreads: An empirical analysis on the informational content of stocks, bonds, and CDS," Journal of Banking & Finance, Elsevier, vol. 33(11), pages 2013-2025, November.
    7. Hanson, Samuel & Schuermann, Til, 2006. "Confidence intervals for probabilities of default," Journal of Banking & Finance, Elsevier, vol. 30(8), pages 2281-2301, August.
    8. Zhu, Haibin & Tarashev, Nikola A., 2008. "The pricing of correlated default risk: evidence from the credit derivatives market," Discussion Paper Series 2: Banking and Financial Studies 2008,09, Deutsche Bundesbank.
    9. Nikola Tarashev & Haibin Zhu, 2008. "Specification and Calibration Errors in Measures of Portfolio Credit Risk: The Case of the ASRF Model," International Journal of Central Banking, International Journal of Central Banking, vol. 4(2), pages 129-173, June.
    10. Kerkhof, Jeroen & Melenberg, Bertrand & Schumacher, Hans, 2010. "Model risk and capital reserves," Journal of Banking & Finance, Elsevier, vol. 34(1), pages 267-279, January.
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    12. Lando, David & Skodeberg, Torben M., 2002. "Analyzing rating transitions and rating drift with continuous observations," Journal of Banking & Finance, Elsevier, vol. 26(2-3), pages 423-444, March.
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    Cited by:

    1. Pflug, Georg Ch. & Pichler, Alois & Wozabal, David, 2012. "The 1/N investment strategy is optimal under high model ambiguity," Journal of Banking & Finance, Elsevier, vol. 36(2), pages 410-417.
    2. repec:eee:finana:v:53:y:2017:i:c:p:80-93 is not listed on IDEAS
    3. Tirupam Goel & Ulf Lewrick & Agnė Nikola Tarashev, 2017. "Bank capital allocation under multiple constraints," BIS Working Papers 666, Bank for International Settlements.
    4. Chollete, Lorán & de la Peña, Victor & Lu, Ching-Chih, 2012. "International diversification: An extreme value approach," Journal of Banking & Finance, Elsevier, vol. 36(3), pages 871-885.
    5. Chollete, Lorán & de la Peña, Victor & Lu, Ching-Chih, 2011. "International diversification: A copula approach," Journal of Banking & Finance, Elsevier, vol. 35(2), pages 403-417, February.
    6. Aussenegg, Wolfgang & Resch, Florian & Winkler, Gerhard, 2011. "Pitfalls and remedies in testing the calibration quality of rating systems," Journal of Banking & Finance, Elsevier, vol. 35(3), pages 698-708, March.
    7. Adonis Antoniades & Nikola Tarashev, 2014. "Securitisations: tranching concentrates uncertainty," BIS Quarterly Review, Bank for International Settlements, December.

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    Keywords

    correlated defaults; estimation error; risk management;

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