Theories of Harm for Digital Mergers


R‌ead the background note


Mergers in digital markets have been much discussed in recent years, following the growing concerns around the acquisition strategies of major tech platforms. In parallel to the well-known debate on killer acquisitions and notification thresholds, new questions have started to emerge about the suitability of existing theories of harm for an effective assessment of mergers in digital markets.

Specific features of digital mergers, such as the prominent role of platform ecosystems relying on strong network effects, high quality algorithms, economies of scale and data-driven economies of scope, bring into question the ability of traditional theories of harm to reflect the real competitive harm that may result from mergers in these markets. Therefore, in order to ensure that anticompetitive transactions can be captured under the existing frameworks for merger review, competition authorities might need to further fine-tune their theories of harm or develop new ones.

In June 2023 the OECD held a roundtable discussing the theories of harm currently used in the analysis of digital mergers, the potential need to develop new ones that could better capture competitive harms, and the challenges that this may bring for competition authorities. 

This page contains all related documentation.

The topic will be explored again on 6 March 2024 during the 2024 OECD Competition Open Day, an event open to the public.


See the full list of best practice roundtables on competition


Luís Cabral Bio  
Paganelli-Bull Professor of Economics, New York University Stern School of Business

Annabelle Gawer Bio  
Professor in Digital Economy & Director, Centre of Digital Economy, University of Surrey

Viktoria Robertson Bio  
Professor of Competition Law, Vienna University of Economics and Business & University of Graz


OECD Background Note | Note de référence de l'OCDE

Note by Viktoria Robertson 

Contributions from participating delegations



European Union








Chinese Taipei

United Kingdom

United States 


Summaries of contributions


Related best practice roundtables

Start-ups, killer acquisitions and merger control (2020)

Competition Economics of Digital Ecosystems (2020)

Quality considerations in the zero-price economy (2018)

Non-price effects of mergers (2018)

Merger control in dynamic markets (2019)

Conglomerate effects of mergers (2020)

The concept of potential competition (2021)

Ex Ante Regulation and Competition in Digital Markets (2021)

Rethinking the use of traditional antitrust enforcement tools in multi-sided markets (2017)

Vertical mergers in the technology, media and telecom sector (2019)

See also

OECD best practice roundtables on competition

More OECD work on competition


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