Platforms like Uber, Google Search, and Hulu pervade the modern economic landscape. A platform caters to distinct but deeply-interdependent “sides” of customers that derive value or revenues from one another, such as the merchants and cardholders on a credit card network, or the advertisers...

Large platforms are often accused of refusing to serve (or discriminating against) competing sellers in adjacent product markets. Antitrust law labels such activity a unilateral “refusal to deal” (RTD) and evaluates it under a predation-like framework shaped by the two leading RTD cases,...