中文摘要
当正式契约无法执行且各方诉诸关系契约时，竞争如何影响市场结果？测量关系契约的困难以及处理竞争的内生性的困难阻碍了回答这一问题的尝试。我们通过研究卢旺达咖啡产业中上游农户与下游加工厂之间的关系契约取得了进展。首先，我们识别了其关系契约的显著维度，并通过对加工厂和农户的原创调查对其进行测量。其次，我们利用加工厂最优选址的工程模型构建了一个工具变量，以分离出由地理决定的竞争变异。在控制集水区内加工厂选址适宜性的条件下，我们发现被更适宜区域环绕的加工厂 面临来自其他加工厂更激烈的竞争， 使用与农户更少的关系契约，以及 表现出更差的绩效。额外增加一个竞争性加工厂还 减少了农户供应给加工厂的咖啡总量，并 使农户境况变差。竞争通过增加农户违约关系契约的诱惑直接阻碍了关系契约，并通过减少加工厂的利润间接阻碍了关系契约。
Abstract
Abstract How does competition affect market outcomes when formal contracts are not enforceable and parties resort to relational contracts? Difficulties with measuring relational contracts and dealing with the endogeneity of competition have frustrated attempts to answer this question. We make progress by studying relational contracts between upstream farmers and downstream mills in Rwanda’s coffee industry. First, we identify salient dimensions of their relational contracts and measure them through an original survey of mills and farmers. Second, we take advantage of an engineering model for the optimal placement of mills to construct an instrument that isolates geographically determined variation in competition. Conditional on the suitability for mills’ placement in the catchment area, we find that mills surrounded by more suitable areas (i) face more competition from other mills, (ii) use fewer relational contracts with farmers, and (iii) exhibit worse performance. An additional competing mill also (iv) reduces the aggregate quantity of coffee supplied to mills by farmers and (v) makes farmers worse off. Competition hampers relational contracts directly by increasing farmers’ temptation to default on the relational contract and indirectly by reducing mills’ profits.