Network Effects, Platforms, and Antitrust Markets: Economic Authority in American Express

In Ohio v. American Express Co., the Supreme Court in 2018 held credit-card companies operate in a two-sided market, and both sides must be considered in evaluating the competitive effects of a company’s conduct. The Court relied on the economics of indirect network effects, as developed in the literature. We argue the Court’s application of the economics literature to resolve the case has established economic authority—authoritative economic knowledge that influences later decisions in mu