This paper studies the impact of market consolidation or fragmentation on its performance, examining four alternative models of exchange: a consolidated clearing house, fragmented clearing houses, a monopoly dealer market, and an interdealer market. The effects of the market mechanism on the expected quantity traded, the price variance faced by individual traders, the quality of market price signals, the expected gains from trade, and the exchange implementation costs are studied.

We study the effect of trading consolidation by examining the response of liquidity and stock price to the exercise of deep in-the-money corporate warrants. This enables a relatively clean test of the value of trading consolidation. The exercise at the warrant expiration is fully anticipated and has no information content. An effect can come from the value of trading consolidation that improves liquidity. Indeed, we find that liquidity and stock prices both increase significantly at warrant expiration. Further, the price increase is positively related to the pre-exercise extent of fragmentation, to post-exercise improvement in stock liquidity, and to the proportional increase in the number of shares following the warrant exercise.