Antitrust Policy for Two-Sided Markets

As technology and interconnectivity have continued to flourish, so too has an important and complex form of enterprise: the platform. Services like Uber, Google Search, Hulu, and American Express cater to distinct but deeply-interdependent “sides” of customers that derive value or revenues from one another, such as the patients and care providers on a health insurance network, or the advertisers and consumers on a social media platform. A hallmark of “two-sided markets”—those in which platforms compete—is the need to get both sides on board. The platform cannot operate successfully without a critical mass of users on both sides, which is often challenging. Platform economics has important implications for antitrust policy, as the interdependence between sides adds new complexity to the evaluation of competitive effects. It becomes critical to discern whether a platform-defendant's conduct is plausibly necessary to get both sides on board. Until recently, courts had dealt with platform commerce only on an ad hoc basis, without articulating any general principles for evaluating restraints within two-sided markets. But the Supreme Court is poised to bring platform competition to antitrust's frontier, as its impending decision in American Express is likely to influence how core aspects of antitrust law and procedure are to be applied within two-sided markets moving forward. Against this backdrop, this article provides a broad analysis of antitrust in two-sided markets. It begins with a discussion of the distinctive features of platform commerce, explaining how they sometimes clash with established intuition and methods in antitrust. The bulk of the paper addresses a wide range of different antitrust concerns that might emerge from platform conduct, with emphasis on discerning when the market's two-sidedness might plausibly justify the practice in question (and when it probably doesn't). The balance of the paper then addresses the issues in American Express—both the market definition and burden shifting questions before the Supreme Court, and the substance of the original antitrust claim