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.

ABSTRACT This paper examines the effects of the mechanism by which securities are traded on their price behavior. We compare the behavior of open‐to‐open and close‐to‐close returns on NYSE stocks, given the differences in execution methods applied in the opening and closing transactions. Opening returns are found to exhibit greater dispersion, greater deviations from normality and a more negative and significant autocorrelation pattern than closing returns. We study the effects of the bid‐ask spread and the price‐adjustment process on the estimated return variances and covariances and discuss the associated biases. We conclude that the trading mechanism has a significant effect on stock price behavior.