This paper studies the effect of the bid-ask spread on asset pricing. We analyze a model in which investors with different expected holding periods trade assets with different relative spreads. The resulting testable hypothesis is that market-observed expexted return is an increasing and concave function of the spread. We test this hypothesis, and the empirical results are consistent with the predictions of the model.

This study considers the problem of a price-setting monopolistic market-maker in a dealership market where the stochastic demand and supply are depicted by price-dependent Poisson processes [following Garman (1976)]. The crux of the analysis is the dependence of the bid-ask prices on the market-maker's stock inventory position. We derive the optimal policy and its characteristics and compare it to Garman's. The results are shown to be consistent with some conjectures and observed phenomena, like the existence of a ‘preferred’ inventory position and the downward monotonicity of the bid-ask prices. For linear demand and supply functions we derive the behavior of the bid-ask spread and show that the transaction-to-transaction price behavior is intertemporally dependent. However, we prove that it is impossible to make a profit on this price dependence by trading against the market-maker. Thus, in this situation, serially dependent price-changes are consistent with the market efficiency hypothesis.

This paper examines the value effects of improvements in the trading mechanism. Selected stocks on the Tel Aviv Stock Exchange were transferred gradually from a daily call auction to a mechanism where the call auction was followed by iterated continuous trading sessions. This event was associated with a positive and permanent price appreciation. The cumulative average market-adjusted return over a period that started five days prior to the announcement and ended 30 days after the stocks started trading by the new method was approximately 5.5%. In addition, we find positive liquidity externalities (spillovers) across related stocks, and improvements in the value discovery process due to the improved trading method. Finally, there was a positive association between liquidity gains and price appreciation.