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Abstract

This article analyses how EU competition law uses insights from behavioural economics to determine whether business conduct is illegal. Various Article 102 TFEU decisions against Microsoft, Google, Amazon, and Apple have reflected behavioural findings on non-rational decision-making, as do obligations imposed on gatekeepers by the Digital Markets Act (DMA). Regardless of whether one accepts the underpinning analysis, behavioural economics is informing EU competition law. The issue is how it should do so. Both Article 102 enforcement and the DMA incorporate behavioural economics in different ways, neither of which is simply a corollary of being “ex post antitrust” or “ex ante regulation”. It is argued that the certainty of Article 102 enforcement would benefit from replicating the DMA’s informed assumptions of irrationality. While the Commission’s current approach of context-specific factual analysis when applying Article 102 faithfully captures the contingency of biases in behavioural economics and facilitates accurate outcomes, it has resulted in uncertainty as to when conduct is prohibited. The DMA’s assumptions of irrationality admittedly distort behavioural economics and will produce some inaccurate outcomes. Nevertheless, if suitably informed by research and enforcement experience, assumptions of irrationality offer the opportunity for Article 102 decisions to reflect behavioural insights without abandoning legal certainty.

Publication Type:	Article
Additional Information:	This is a pre-copyedited, author-produced version of an article accepted for publication in Journal of Antitrust Enforcement following peer review. The version of record Stones, R. (2025). Behavioural Economics in EU Competition Law: Article 102 TFEU, the Digital Markets Act, and Informed Assumptions of Irrationality. Journal of Antitrust Enforcement will be available online at: https://academic.oup.com/antitrust
Subjects:	H Social Sciences > HB Economic Theory K Law > K Law (General)
Departments:	The City Law School The City Law School > Academic Programmes
SWORD Depositor:	Symplectic Administrator

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