Regulatory interventions aimed at promoting competition in digital markets face a challenge: how to design remedies that actually improve welfare? This Article helps provide an answer to this question. First, it maps out the frontier of remedy design: Part I.A summarizes antitrust and regulatory...

The American Supreme Court decision in Ohio v. American Express (AMEX) will shape the future of US antitrust enforcement on multi-sided platforms. In a controversial landmark ruling, both the Court's majority and minority battled over definitions of relevant markets in the complex industry of...

While the various initiatives in several jurisdictions to impose ex ante regulation on “digital gatekeepers” – i.e., large online platforms that are necessary intermediaries between business users and their customers, and which are typically protected by high barriers to entry – have...

We review the burgeoning literature on two-sided markets focusing on the different definitions that have been proposed. In particular, we show that the well-known definition given by Evans is a particular case of the more general definition proposed by Rochet and Tirole. We then identify the...