Law Commons^™

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

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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

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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 …

Error Costs, Legal Standards Of Proof And Statistical Significance, Michelle Burtis, Jonah B. Gelbach, Bruce H. Kobayashi

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The relationship between legal standards of proof and thresholds of statistical significance is a well-known and studied phenomena in the academic literature. Moreover, the distinction between the two has been recognized in law. For example, in Matrix v. Siracusano, the Court unanimously rejected the petitioner’s argument that the issue of materiality in a securities class action can be defined by the presence or absence of a statistically significant effect. However, in other contexts, thresholds based on fixed significance levels imported from academic settings continue to be used as a legal standard of proof. Our positive analysis demonstrates how a …

A General Approach For Predicting The Behavior Of The Supreme Court Of The United States, Daniel Katz

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Building on developments in machine learning and prior work in the science of judicial prediction, we construct a model designed to predict the behavior of the Supreme Court of the United States in a generalized, out-of-sample context. To do so, we develop a time-evolving random forest classifier that leverages unique feature engineering to predict more than 240,000 justice votes and 28,000 cases outcomes over nearly two centuries (1816-2015). Using only data available prior to decision, our model outperforms null (baseline) models at both the justice and case level under both parametric and non-parametric tests. Over nearly two centuries, we achieve …

The Reduced Form Of Litigation Models And The Plaintiff's Win Rate, Jonah B. Gelbach

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In this paper I introduce what I call the reduced form approach to studying the plaintiff's win rate in litigation selection models. A reduced form comprises a joint distribution of plaintiff's and defendant's beliefs concerning the probability that the plaintiff would win in the event a dispute were litigated; a conditional win rate function that tells us the actual probability of a plaintiff win in the event of litigation, given the parties' subjective beliefs; and a litigation rule that provides the probability that a case will be litigated given the two parties' beliefs. I show how models with very different-looking …

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

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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

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No abstract provided.

Bounded Rationality And Legal Scholarship, Matthew D. Adler

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Decision theory seems to offer a very attractive normative framework for individual and social choice under uncertainty. The decisionmaker should think of her choice situation, at any given moment, in terms of a set of possible outcomes, that is, specifications of the possible consequences of choice, described in light of the decisionmaker’s goals; a set of possible actions; and a "state set" consisting of possible prior "states of the world." It is this framework for choice which provides the foundation for expected utility theory, as demonstrated in the work of Leonard Savage. Problems arise, however, when the decisionmaker is boundedly …

Against 'Individual Risk': A Sympathetic Critique Of Risk Assessment, Matthew D. Adler

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"Individual risk" currently plays a major role in risk assessment and in the regulatory practices of the health and safety agencies that employ risk assessment, such as EPA, FDA, OSHA, NRC, CPSC, and others. Risk assessors use the term "population risk" to mean the number of deaths caused by some hazard. By contrast, "individual risk" is the incremental probability of death that the hazard imposes on some particular person. Regulatory decision procedures keyed to individual risk are widespread. This is true both for the regulation of toxic chemicals (the heartland of risk assessment), and for other health hazards, such as …

Incentives To Settle Under Joint And Several Liability: An Empirical Analysis Of Superfund Litigation, Howard F. Chang, Hilary Sigman

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Congress may soon restrict joint and several liability for cleanup of contaminated sites under Superfund. We explore whether this change would discourage settlements and is therefore likely to increase the program 's already high litigation costs per site. Recent theoretical research by Kornhauser and Revesz finds that joint and several liability may either encourage or discourage settlement, depending on the correlation of outcomes at trial across defendants. We extend their two-defendant model to a richer framework with N defendants. This extension allows us to test the theoretical model empirically using data on Superfund litigation. We find that joint and several …

Almost Everybody Disagrees Almost All The Time: The Genericity Of Weakly Merging Nowhere, Ronald I. Miller, Chris William Sanchirico

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Suppose we randomly pull two agents from a population and ask them to observe an unfolding, infinite sequence of zeros and ones. If each agent starts with a prior belief about the true sequence and updates this belief on revelation of successive observations, what is the chance that the two agents will come to agree on the likelihood that the next draw is a one? In this paper we show that there is no chance. More formally, we show that under a very unrestrictive definition of what it means to draw priors “randomly,” the probability that two priors have any …

Uncertainty, Efficiency, And The Brokerage Industry, Michael S. Knoll

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No abstract provided.