market liquidity and trading of other market participants. IDT contribute 10% to volume while losing 3.2 bp (73% of the half …-spread) on average on trades with others, including proprietary day traders (PDT), the primary intraday-liquidity providers, and … activity. This pattern is consistent with competition among PDT. Our results highlight the importance of IDT's presence in …

with our theory, we document improvements in liquidity and lower profits for liquidity providers when Euronext, in 2009 … intermediaries at the expense of investors with intrinsic trading motives, and lower liquidity than consolidated markets. Consistent … book. Our results suggest that competition in market design, not fragmentation, drives previously documented improvements …