EThere has been intensive research on the impact and effects of the SEC regulation
reform on trading structure. Barclay et al [4] have examined the impact
and effects of market reform on the trading costs and depths on Nasdaq stocks.
Their major result was that the restructuring of Nasdaq market have produced
a more competitive and effcient trading system on Nasdaq. The authors quantified
the impact of these new rules on various performance and effciency indicators
such as trading costs and liquidity. They found that quoted and effective
spreads fell dramatically without affecting the market effciency.
The target of theses reforms was to o¤er to investors more competitive
quotes through the mandatory display of customer limit orders and the dissemination
of superior prices placed in ECN. Although this new reform was