12.I Introduction

MiFID I1 broke down the optional ISD concentration-rule. In addition to opening up competition among trading services, MiFID I introduced competition in the market for data services.2 MiFID I did this by permitting choice with respect to publication services and by relying on market-driven consolidation of equity pre- and post-trade data (bottom-up). The EU acknowledged that the bottom-up approach embodied the possibility that equity pre- and post-trade data could fragment across RMs, MTFs, and investment firms operating outside such venues (including SIs).3 Fragmentation of equity pre- and post-trade data, if not addressed properly, could undermine the overarching transparency objective of MiFID I.4 Fragmentation could result in less transparent markets than was the case in the concentrated market setting during the ISD.5 For this reason, the EU introduced some top-down elements under MiFID I, in particular for publication (not: consolidation) arrangements. In practice, the most substantial amount of ‘rules’ came from CESR, which provided guidelines and recommendations.6