Comparative Impacts of Ex-Ante and Ex-Post Regulation in Digital Markets: An Event Study Analysis of Stock Price Reactions

Arai Koki ()
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Arai Koki: Faculty of Business Studies, Kyoritsu Women’s University, Tokyo, Japan

Asian Journal of Law and Economics, 2025, vol. 16, issue 2, 283-305

Abstract: In the analysis of digital markets and competition, it is imperative to consider the regulatory landscape. Specifically, with the shift from ex post to ex ante regulation in competition law, establishing a competitive environment reflective of regulatory costs becomes imperative. This study investigates the market’s assessment of ex ante regulation through stock price event analysis. The findings reveal that the market perceives a 10–20 % negative impact on businesses from ex ante regulation for each event upon finalization of the regulatory framework or identification of regulated entities. Unlike ex-post regulation, which targets specific businesses and yields varied impacts in competition law violations, ex ante regulation’s broader influence is remarkable. ex ante regulation incurs significant business costs, with the market assessing its impact as surpassing that of ex-post regulation when viewed holistically. Acknowledging these regulatory costs underscores the imperative for stringent oversight to guarantee the attainment of regulatory aims and objectives.

Keywords: digital platform; digital platform transparency act; market evaluation; stock price event analysis (search for similar items in EconPapers)
JEL-codes: K21 K23 L51 M38 (search for similar items in EconPapers)
Date: 2025
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DOI: 10.1515/ajle-2024-2002

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