Antitrust policy towards firms that “leverage” their market power to grant themselves competitive advantages in adjacent markets has come to the fore in recent times with the growth of digital platforms in sectors such as online search, mobile operating systems, online marketplaces and social media. This Article analyzes the historical origins and Chicago critique of the leverage doctrine and how these informed the development of antitrust policy. Antitrust law currently distinguishes between pro- and anti-competitive leveraging in order to achieve the optimal balance between promoting competition in adjacent markets and preserving the legitimate ability of platform owners to enter and compete in adjacent markets. Thus, leveraging is only unlawful under the Sherman Act when it results in consumer harm. The Article then considers recent proposals to address perceived competition issues in digital platform markets, which condemn leveraging even if it benefits consumers in order to protect competitors in adjacent markets from competition on the merits. Empirical criteria that have been present in comparable instances of such intervention, such as bottleneck power over distribution, widespread harm to adjacent market competition, static product boundaries, and a lack or unimportance of integrative efficiencies, are not satisfied in the current context. Absent some proof that they are, the consumer welfare framework under antitrust law should prevail without recourse to more intrusive intervention.

I. Introduction

II. Leveraging by Digital Platform Owners ... A. Leveraging Concerns in Digital Markets ... B. Examples ... 1. Online Search ... 2. Mobile Operating Systems ... 3. Online Marketplaces ... 4. Social Media

III. Leveraging in Antitrust Law ... A. The Historical Origins of the Leverage Doctrine ... B. The Chicago Critique of the Leverage Doctrine ... C. The Impact of the Chicago Critique on Adjacent Market Entry and Leveraging ... D. Efficiency Justifications that Benefit Consumers ... 1. Efficiencies from Adjacent Market Entry ... 2. Efficiencies from Leveraging ... E. Distinguishing Anti-Competitive from Pro-Competitive Leveraging

IV. Abrogating Consumer Welfare in Favor of Small Business Welfare ... A. Proposals to Regulate Adjacent Market Competition ... 1. Structural Separation ... 2. Non-Discrimination Principles ... 3. Burden Reallocation ... B. Empirical Criteria for Abrogating Consumer Welfare ... 1. Strategic Bottleneck Power ... 2. Widespread Harm in Adjacent Markets ... 3. Static Product Boundaries ... 4. Lack or Unimportance of Integration Efficiencies

V. Conclusion