Structural presumptions in antitrust law refer to the concept that certain market structures, including high market shares and concentration, may presumptively harm competition and consumers. Once 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 presumption in antitrust enforcement continues to animate debates among competition authorities, academics and practitioners, reflecting different views on their relevance, application and accuracy when assessing potential anticompetitive practices. This paper explores how the use of structural presumptions may enable competition authorities to simplify complex issues related to market analysis and accelerate the competitive process, while maintaining the required degree of legal certainty to achieve the desired outcome. These mechanisms can ultimately make competition enforcement more predictable, transparent and efficient. Yet their use may also increase potential error costs, requiring competition authorities to consider trade-offs between different enforcement strategies (e.g. certainty, administrability and efficiency in decision-making versus accuracy). This paper also analyses the balancing of structural presumptions against detailed economic analysis which can be crucial to ensure fair and effective antitrust enforcement.
