Jurisdiction(s):
United Kingdom

Related legal acts

Key definition

Market definition definition

What does Market definition mean? Market definition describes, in practical terms, the process of identifying the products and geographic area within which firms compete, as the frame for assessing market power, dominance and competitive effects. It is typically the starting point in competition law analyses of merger control, abuse of dominance and restrictive agreements. In the UK and Ireland it is not set by statute but developed through case law and authority guidance (in particular from the CMA, the CCPC and, where EU law applies, the European Commission’s Market Definition Notice). The exercise delineates the relevant product market and relevant geographic market, focussing primarily...

Defining Relevant Product and Geographic Markets in EU and UK Competition Law: HMT, Evidence, CMA and European Commission Practice, and Challenges in Mergers, Agreements and Dominance

Published by a LexisNexis Competition expert

Practice notes

Introduction

Defining the Relevant market is traditionally the first step in most Competition law analysis. It offers an impartial conceptual structure for systematically pinpointing competitors (or potential competitors) that may constrain a firm’s behaviour. The European Commission (Commission) describes these forces as ‘effective and immediate competitive constraints’. Competition authorities use Market definition in several contexts, in particular for merger control, the assessment of anti-competitive agreements, and abuse of dominance cases.

merger control — competition authorities appraise the impact of the proposed merger. For this purpose, the Commission and the Competition and Markets Authority (CMA) delineate the markets in which the merging parties operate, and the competitive pressure the combined entity would encounter within those markets
anti-competitive agreements — when authorities suspect a restrictive agreement between suppliers or purchasers, they typically examine whether it generated anti-competitive effects. This entails defining the markets that may have been influenced by the agreement
abuse of dominance cases — authorities consider whether the company under investigation holds significant Market power and has leveraged that position to distort competition...

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Paul Reeve

RBB Economics

Paul is a Partner in RBB’s London office, having joined the firm in 2020. Paul has worked as a competition economist for nearly 20 years, in consultancy, regulators and industry. He has particular expertise in UK merger control, having worked for much of the last decade at the CMA and its predecessor, the CC. Paul has worked on around 100 UK mergers, and was the lead economist on several Phase 2 cases, most notably BT/EE. He was the head of economics in Phase 1 mergers, leading a team of economists in cases across numerous sectors. Paul is a former chair of the CMA’s Mergers Intelligence Committee, responsible for deciding which mergers should be investigated. He also acted as a Director on several merger cases, and led the development of merger policy in several areas including retail mergers. He was the primary author of the CMA’s Rail...

Léa Julienne-Ista

RBB Economics

Léa is a Senior Associate based in the Paris office of RBB Economics, where she has worked since 2018. Her experience includes merger assessments, abuse of dominant position, horizontal and vertical agreements, as well as follow-on damages. Since joining RBB, Léa had advised on a wide variety of competition cases before the European Commission and domestic authorities. Léa’s sectoral experience expands a wide range of sectors, including internet search, TV broadcasting, advertising, white goods, supermarket, and various industrial goods. ...

Mert Bakirci

RBB Economics

Mert Bakirci is a Senior Associate at RBB Economics, based in Düsseldorf. Since joining RBB in 2020, he has advised clients on a variety of competition matters, including abuse of dominance investigations, follow-on damage litigations, and merger control procedures. Mert has provided advice on matters before competition authorities and courts at both the EU and national levels, most notably in the UK, Germany, Austria, and Turkey. His experience spans several industries, including medical devices, ophthalmic products, trucks, and consumer goods, as well as sports betting data and football transfer markets....

Web page updated on 21/05/2026

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