Antitrust laws and regulations aim to promote effective competition and prevent business practices that hamper competition. Structural presumptions in antitrust law refer to the general concept that certain market structures, including high market shares and concentration, are considered presumptively to harm competition and consumers (presumption of illegality). Once structural presumptions are established by competition authorities or courts, the burden of proof typically shifts to the firms which need to rebut these presumptions.
The use of structural presumptions may simplify and streamline the establishment of infringements in complex cases and facilitate the enforcement process. However, their use may also increase potential error-costs, requiring competition authorities or courts to consider potential trade-offs between different enforcement strategies.
Striking a balance between structural presumptions and in-depth economic analysis is crucial to ensure fair and effective antitrust enforcement.
This paper was prepared by Giorgio Castaldo and Songrim Koo from the OECD Competition Division. The paper benefited from comments by Ori Schwartz, Antonio Capobianco, Maria Canedo and Richard May from the OECD Competition Division and research by Christine Kim from the OECD Competition Division.
It was prepared to serve as background material for discussions on “The use of structural presumptions in antitrust” taking place at the December 2024 session of Working Party No. 3 on Co-operation and Enforcement meeting on 4 December 2024.