The notion of market power is central to antitrust law. Under EU law, antitrust rules refer to appreciable restrictions of competition (Article 101 (1) TFEU, ex Article 81(1) TEC), the elimination of competition for a substantial part of the market (Article 101 (3) TFEU, ex Article (81(3) TEC), dominant positions (Article 10 2 TFEU, ex Article 82 TEC), and substantial impediment to effective competition, in particular by creating or reinforcing a dominant position (Article 2 of the EU Merger Regulation). At first sight, only the concept of dominant position relates to market power, but this...