Demystifying Causation in Fraud-on-The-Market Actions

41 Pages Posted: 18 Jan 2005

See all articles by Merritt B. Fox

Merritt B. Fox

Columbia University - Law School


This Article concerns what an investor who purchases shares on the open market of an issuer that has made a positive, materially false misstatement in violation of Rule 10b-5 must show to establish causation in a fraud-on-the-market action for damages. Confusion has arisen in the courts concerning this question because they have analyzed the matter in terms of the twin concepts of transaction causation and loss causation. They initially developed these concepts as a way of deciding causation in actions based on a showing of traditional reliance. Fraud-on-the-market actions involve a fundamentally different kind of causal connection, between the defendant's misstatement and the plaintiff's injury, as recognized by the Supreme Court in Basic v. Levinson. Because of this fundamental difference is causal connection, the twin concepts of transaction causation and loss causation simply do not make sense in fraud-on-the-market actions.

The focus in fraud-on-the-market cases should instead be on developing standards for what the plaintiff must plead and prove, and the acceptable forms of evidence, in order to establish that the defendant's misstatement inflated the price at the time of purchase. Analyzing the problem from the ex ante perspective of the economics based approach to securities law reveals that these are the real issues underlying the causation cases coming before the courts.

Suggested Citation

Fox, Merritt B., Demystifying Causation in Fraud-on-The-Market Actions. Available at SSRN:

Merritt B. Fox (Contact Author)

Columbia University - Law School ( email )

435 West 116th Street
New York, NY 10025
United States

Do you have a job opening that you would like to promote on SSRN?

Paper statistics

Abstract Views
PlumX Metrics