In their paper Messrs. Reilly and Slaughter set out two questions, namely:

1. Prior to the introduction of technological advance in the securities market was there any difference in the market making between the NYSE and OTC on a sample of 30 stocks?

2. Following that introduction what was the effect on the market making of these securities listed on the NYSE?

The authors clearly stated the basic economic theory that underlies this exchange of assets and the price setting mechanism, and then concentrated on the empirical study. Their findings are inconsistent with their a priori expectations. This empirical study is well done; the methodology is sound and well presented. However, the authors appear to have overlooked one vital aspect of this type of study, i.e., institutional effects. I shall concentrate upon this area.