This paper examines the degree of anonymity—the extent to which a trader is recognized as informed—on alternative market structures. We find evidence that is consistent with less anonymity on the NYSE specialist system compared to the NASDAQ dealer system. Specifically, when corporate insiders trade medium-sized quantities (500–9, 999 shares inclusive), NYSE listed stocks exhibit larger changes in proportional effective spreads than NASDAQ stocks. Taken together, these findings are consistent with Barclay and Warners (1993) contention that stealth (medium-sized) trades are more likely based on private information and insider trades are more transparent on the NYSE specialist system relative to the NASDAQ dealer system. The results support the hypothesis by Benveniste, Marcus, and Wilhelm (1992) that the unique relationship between specialists and floor brokers on the NYSE leads to less anonymity.

This paper addresses the issue of the optimal trading system for less actively traded (i.e., ‘thinly-traded’) stocks. We compare the performance of a pure order driven market with limit order book (POD) with that of a hybrid order driven market with specialist and limit order book (HOD). We find that the HOD system offers superior performance along several dimensions of market quality. In particular, the specialist-based system offers lower execution costs, greater depth, a significant increase in the depth-to-spread ratio, and lower adverse selection costs. Very ‘thinly-traded’ stocks benefit more than less inactive stocks from the adoption of a hybrid trading system both in terms of greater liquidity and in terms of lower adverse selection costs.