Consolidation, fragmentation, and the disclosure of trading information

It is commonly believed that fragmented security markets havea natural tendency to consolidate. This article examines thisbelief, focusing on the effect of disclosing trading informationto market participants. We show that large traders who placemultiple trades can benefit from the absence of trade disclosurein a fragmented market, as can dealers who face less price competitionthan in a unified market. Consequently, a fragmented marketneed not coalesce into a single market unless trade disclosureis mandatory. We also compare and contrast fragmented and consolidatedmarkets. Fragmentation results in higher price volatility andviolations of price efficiency.