MIDDLEMEN IN SEARCH EQUILIBRIUM WITH INTENSIVE AND EXTENSIVE MARGINS
研究了内生中介活动及其对交易模式（直接或间接交易）和效率的影响，通过引入可分性（代表数量或质量）来捕捉集约边际，分析了议价能力和成本如何影响均衡，并设计了实现效率的税收补贴政策。
Abstract We study endogenous intermediation activity, the implied transaction pattern—direct trade, indirect trade, or both—and implications for efficiency. Related papers have agents exchanging indivisible goods or assets, capturing only extensive margins (trade frequency). To capture intensive margins, we incorporate divisibility representing quantity or quality. We characterize equilibrium, show how it depends on bargaining powers and costs, and how intensive margins matter—for example, middlemen with high bargaining power may charge more but offer higher quantity/quality, thus improving welfare. A tax‐subsidy policy is designed to achieve efficiency. A monetary version lets us compare money and middlemen and further discuss policy.