Professor Louis Kaplow has argued that market delineation in antitrust should be abandoned because it is not useful in assessing market power or evaluating competitive effects. This article takes issue with that view, explaining that market delineation serves purposes overlooked by Professor...

The U.S. Horizontal Merger Guidelines and guidelines issued by enforcement agencies around the world employ the hypothetical monopolist paradigm to delineate relevant markets, but they provide only an imprecise and incomplete algorithm for implementing that paradigm. This paper fills the gap by...

"Critical elasticity of demand" and "critical loss" analysis are now standard analytical tools for implementing the hypothetical monopolist paradigm for market delineation. Although these tools are highly useful, this paper presents three scenarios in which their standard application can be...

On January 10, 2022, the U.S. Department of Justice and Federal Trade Commission issued a Request for Information on Merger Enforcement designed to elicit input in the preparation of guidelines replacing both the 2010 Horizontal Merger Guidelines and the 2019 Vertical Merger Guidelines. The RFI...

The legality of a horizontal merger under section 7 of the Clayton Act turns on a reckoning of its social costs and benefits. This paper reviews what economics has to say about that reckoning and explores the relationship between economic learning and merger law and policy

On July 18, 2023, the Agencies responsible for enforcing antitrust law relating to mergers—the U.S. Department of Justice and the Federal Trade Commission—published draft Merger Guidelines (dMGs) for comment. This comment reflects cumulative experience from four decades as an enforcer, from...

The European Commission sought public comment on a revision of its Notice on the definition of the relevant market. Among other things, this contribution advises the Commission to: acknowledge the analytic purpose served by the relevant market in competitive assessment; apply the hypothetical...

Robert Crandall and Clifford Winston set out to review and enlarge the body of scholarly evidence on the effect of antitrust policy on consumer prices. They ignore, however, the great weight of evidence supporting the two core elements of antitrust policy - criminal prosecution of cartel...

Inconvenient truths prevent econometric merger retrospective studies from substantially altering our understanding of competitive effects from horizontal mergers. Econometrics cannot definitively determine the effects of particular mergers, and if they could, econometric merger retrospectives...

In FTC v. Lundbeck, courts rejected a challenge to an acquisition placing under common control the only two drugs for treating a heart defect in newborns. Although the court decisions in the case have been severely criticized, they might well have achieved the right result for the right reason....