<i>Microsoft/Activision Blizzard</i> and <i>Booking/eTraveli</i> : an ecosystem market definition in five takeaways

Abstract In 2023, the EU prohibited Booking/eTraveli whilst the UK sought to prohibit Microsoft/Activision Blizzard. In both cases, the other authority allowed the merger. The decisions reveal the existence of two issues: a Disconnect Inconsistency in the prohibitions (between (platform-based) market definition and (ecosystem-level) assessment) and a Static/Dynamic Divide (prohibitions grounded in forward-looking ecosystem concerns and clearances grounded in traditional, static indicators). In light of these observations, a workable market definition is proposed: an ecosystem market is a multi-product, multi-actor system, orchestrated by a central firm, which competes as a unit against other such systems. This definition aligns market boundaries with the merger assessment and provides the authorities with a coherent frame for analysing competition both within and between ecosystems. The analysis leads to five takeaways: (i) the two cases reveal analytical and methodological inconsistencies in the practice of the competition authorities; (ii) the proposed definition can guide the authorities towards legally sound, forward-looking merger control; (iii) qualitative and quantitative tools exist to operationalize ecosystem definition and assessment; (iv) market definition remains legally and practically indispensable for consistency and legal robustness of merger control; and (v) when ecosystems compete, the merger question becomes inherently structural, requiring a focus on market definition.