Estimating asset correlations from stock prices or default rates: which method is superior?

Klaus Düllmann, Michael Kunisch and Jonathan Küll

No 2008,04, Discussion Paper Series 2: Banking and Financial Studies from Deutsche Bundesbank

Abstract: This paper sets out to help explain why estimates of asset correlations based on equity prices tend to be considerably higher than estimates based on default rates. Resolving this empirical puzzle is highly important because, firstly, asset correlations are a key driver of credit risk and, secondly, both data sources are widely used to calibrate risk models of financial institutions. By means of a simulation study, we explore the hypothesis that differences in the correlation estimates are due to a substantial downward bias characteristic of estimates based on default rates. Our results suggest that correlation estimates from equity returns are more efficient than those from default rates. This finding still holds if the model is misspecified such that asset correlations follow a Vasicek process which affects foremost the estimates from equity returns. The results lend support for the hypothesis that the downward bias of default-rate based estimates is an important although not the only factor to explain the differences in correlation estimates. Furthermore, our results help to quantify the estimation error of asset correlations dependent on the risk characteristics of the underlying data base.

Keywords: Asset correlation; single risk factor model; small sample properties; structural model; Basel II (search for similar items in EconPapers)
JEL-codes: C13 G21 G33 (search for similar items in EconPapers)
Date: 2008
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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