Law Commons^™

Power And Statistical Significance In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach

All Faculty Scholarship

Event studies, a half-century-old approach to measuring the effect of events on stock prices, are now ubiquitous in securities fraud litigation. In determining whether the event study demonstrates a price effect, expert witnesses typically base their conclusion on whether the results are statistically significant at the 95% confidence level, a threshold that is drawn from the academic literature. As a positive matter, this represents a disconnect with legal standards of proof. As a normative matter, it may reduce enforcement of fraud claims because litigation event studies typically involve quite low statistical power even for large-scale frauds.

This paper, written for …

The Logic And Limits Of Event Studies In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach, Jonathan Klick

All Faculty Scholarship

Event studies have become increasingly important in securities fraud litigation after the Supreme Court’s decision in Halliburton II. Litigants have used event study methodology, which empirically analyzes the relationship between the disclosure of corporate information and the issuer’s stock price, to provide evidence in the evaluation of key elements of federal securities fraud, including materiality, reliance, causation, and damages. As the use of event studies grows and they increasingly serve a gatekeeping function in determining whether litigation will proceed beyond a preliminary stage, it will be critical for courts to use them correctly.

This Article explores an array of …

Can We Learn Anything About Pleading Changes From Existing Data?, Jonah B. Gelbach

All Faculty Scholarship

In light of the gateway role that the pleading standard can play in our civil litigation system, measuring the empirical effects of pleading policy changes embodied in the Supreme Court's controversial Twombly and Iqbal cases is important. In my earlier paper, Locking the Doors to Discovery, I argued that in doing so, special care is required in formulating the object of empirical study. Taking party behavior seriously, as Locking the Doors does, leads to empirical results suggesting that Twombly and Iqbal have had substantial effects among cases that face Rule 12(b)(6) motions post-Iqbal. This paper responds to …

Expert Mining And Required Disclosure, Jonah B. Gelbach

All Faculty Scholarship

No abstract provided.