A. INTRODUCTION As we are rapidly nearing the fifteenth anniversary of the original EC Merger Regulation (ECMR), 1 European merger control is evolving by adopting a more reasoned approach to the substantive merger analysis of competitive injury. That approach has embraced the economics of antitrust in a significant, more thoughtful, thorough and focussed way. The European Commission’s shift in emphasis is exemplified, in particular, by: (i) the creation of the position of Chief Economist, with independent resources and a reporting line to the Commissioner, to strengthen the economic rigour of Commission decisions; (ii) the subordination of the dominance test, rooted in less-than-solid theoretical ground, to the ‘significant impediment to effective competition” test (SIEC); 2 (iii) the production of guidelines on horizontal mergers, 3 outlining the analytical approach to be used, with guidelines on vertical and conglomerate mergers awaited; and (iv) the reversal of the Commission’s historically critical attitude towards efficiencies in favour of an approach that rests more easily with established economic thinking that efficiencies can be pro-competitive. The European Court of Justice has bolstered this approach in Airtours 4 in relation to collective dominance, and in Tetra 5 in