Market Definition for Two-Sided Platforms : Why Ohio v. American Express Co. Matters for the Big Tech

This Essay stresses the importance of the U.S. Supreme Court's decision in Ohio v. American Express Co. (Amex) for the “Big Tech” (Amazon, Apple, Facebook, and Google) and its pertinence to the current antitrust battles facing the four companies. After bringing up the concepts of two-sidedness and indirect network effects and presenting the Court's holding in Amex, this Essay calls attention to the implications of the opinion for the two-sided platforms of the Big Tech. First, the decision offers lucid insights for the antitrust scrutiny of Amazon's merchant platform, Marketplace. Second, the Amex Court's market definition analysis, if extended to the European Commission's Google Search (Shopping) case, suffices to relieve Google of its dominance in the case. Third, Amex can be read as an omen of the nonapplication of the Illinois Brick Co. v. Illinois rule in Pepper v. Apple Inc. Fourth, further guidance is required with respect to market definition in non-transaction platforms, such as Facebook, which are not affected by the Court's decision