Avoiding Market Definition Under Section 1 of the Sherman Act

By Johnny Shaw

The 2018 U.S. Supreme Court decision in Ohio v. American Express Co. was at odds with a trend among antitrust commentators and enforcement authorities away from dependence on formal market definition as part of plaintiffs’ burden of proof. Reliance on market definition as a dispositive issue has been ubiquitous in antitrust cases, but the costs from errors, inefficiency, and uncertainty inherent in that approach are glaring. The issue is ripe for clarification, and this Note suggests a new rule to that end. The proposed rule aims to delineate a set of cases in which formal market definition can confidently be dispensed with, in the hopes of reducing uncertainty in antitrust cases and streamlining their administration.