Disaggregating Market Definition: AmEx and a Plural View of Market Definition

26 Pages Posted: 17 Aug 2021 Last revised: 20 Aug 2021

See all articles by Daniel Francis

Daniel Francis

New York University School of Law

Jay Ezrielev


Date Written: 2019


The orthodox view of market definition in antitrust cases is that the same principles of market definition should apply at all stages of an antitrust analysis, and, in particular, that markets should be defined for virtually all purposes by reference to demand-side substitutability. Commentators have struggled to reconcile the Supreme Court's recent decision in Ohio v. American Express Co. --in which the majority combined services to cardholders and services to merchants into a single antitrust market, despite the evident lack of substitutability between them -- with that familiar view.

In this short Article, we suggest that this effort at reconciliation may be unnecessary, and perhaps even undesirable. Against the orthodox view, we claim that market definition should be "disaggregated" such that the correct approach to market definition may vary depending on the element of the antitrust analysis for which it is being used. Thus, while market definition based on substitutability is an appealing tool for the assessment of market power, it may not be appropriate for the evaluation of competitive effects in all cases under Section 1 of the Sherman Act. The majority opinion in AmEx can (and perhaps should) be understood as an implicit-albeit cryptic-endorsement of a disaggregated approach to market definition.

Keywords: antitrust, platform, American Express, Sherman Act, market definition

Suggested Citation

Francis, Daniel and Ezrielev, Jay, Disaggregating Market Definition: AmEx and a Plural View of Market Definition (2019). Nebraska Law Review, Vol. 98, 2019, Available at SSRN: https://ssrn.com/abstract=3888300

Daniel Francis (Contact Author)

New York University School of Law ( email )

40 Washington Square South
New York, NY 10012-1099
United States

HOME PAGE: http://rb.gy/x7bcq1

Jay Ezrielev

Elevecon ( email )

United States

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