Law Commons^™

Idiosyncratic Risk During Economic Downturns: Implications For The Use Of Event Studies In Securities Litigation, Edward G. Fox, Merritt B. Fox, Ronald J. Gilson

Faculty Scholarship

We reported in a recent paper that during the 2008-09 financial crisis, for the average firm, idiosyncratic risk, as measured by variance, increased by five-fold. This finding is important for securities litigation because idiosyncratic risk plays a central role in event study methodology. Event studies are commonly used in securities litigation to determine materiality and loss causation. Many bits of news affect an issuer’s share price at the time of a corporate disclosure that is the subject of litigation. Because of this, even if an issuer’s market–adjusted price changes at the time of the disclosure, one cannot determine with certainty …