We show that competitive quotes help increase dealer market share on NASDAQ, despite the fact that a large proportion of order flow is preferenced. We find that decimal pricing and the introduction of new trading platforms such as SuperSOES and SuperMontage have significantly changed the effect of quote aggressiveness on dealer market share. In particular, decimal pricing reduces (increases) the price (size) elasticity, SuperSOES increases the size elasticity, and SuperMontage increases both the size and price elasticity of dealer market share. We also show that market centers provide greater price improvements and faster executions when they post competitive quotes.

The Securities and Exchange Commission (SEC) adopted Rule 605 (formerly Rule 11Ac1–5) on November 15, 2000. The Rule requires market centers to make monthly public disclosure of execution quality. The Rule is intended to achieve a more competitive and efficient national market system by increasing the visibility of execution quality. The effective and quoted spreads for our study sample of NYSE, AMEX, and NASDAQ stocks declined significantly after implementation of the Rule. The decline cannot be attributed to a secular trend in spreads, concurrent changes in stock attributes, or the effect of decimal pricing. Although the quoted depth of NYSE stocks also declined, overall market quality is higher after implementation of the Rule. Based on these results, we conclude that the SEC's goal to improve execution quality through more transparent markets has been achieved.