Equilibrium Bid-Ask Spreads in Markets with Multiple Assets
把做市商系统建模为垄断竞争市场，通过求解投资者在交易成本下的资产组合问题得到需求方程，再用于做市商的定价决策，分析了资产、投资者特征及资产数量如何影响均衡价格和投资组合，并讨论了资产数量增加时买卖价差收敛到竞争水平以及垄断竞争与合谋市场的预测差异。
The paper models the specialist system as a monopolistically competitive market. The demand for the asset is found by solving the investor's portfolio problem with transactions costs. These demand equations are used as inputs in the specialist's price-setting problem. It is shown that equilibrium prices and hence equilibrium portfolio holdings depend upon the characteristics of the assets and the investors and the number of assets being traded. Conditions are given under which the bid and ask prices will converge to the competitive level as the number of assets increases. Predictive differences between a monopolistically competitive market and a market where specialists collude are also discussed.