中文摘要
为衡量正式契约的执行给社会带来的收益，我构建了一个由商人与买方组成的市场，其中买方可以选择是否购买以及是否付款。多个“受国家偏袒”的族群控制着国家。我通过实验改变是否要求使用正式契约，以及买方—商人配对的构成。该设计分别识别了契约对买方付款激励和购买激励的影响。我记录了社会限制契约收益的两种方式。第一，当且仅当商人受到国家偏袒时，契约才会减少买方欺诈行为，从而增加商人的利润。买方的信念表明，当且仅当商人受到国家偏袒时，商人才能执行契约。第二，在保持配对是否受到国家偏袒这一条件不变的情况下，契约仅在买方和商人分属两个不同的、受国家偏袒的族群时影响买方的选择。买方的选择与信念证实，在这种情况下，契约被预期为可执行的，但并不影响买方的选择，因为声誉已经在族群内部制约了欺诈激励。这些发现使我们对国家独立于社会的观点有所保留，为契约为何未被采用提供了解释，并使对国家软弱这一概念的理解更为细致。
Abstract
To measure the benefits of formal contract enforcement for society, I create a market with merchants and buyers, in which buyers can choose whether to buy, and whether to pay. A set of multiple “state‐favored” ethnic groups control the state. I experimentally vary whether formal contracts are required and the composition of buyer‐merchant pairs. The design separately identifies the effect of the contracts on the buyers' incentive to pay and on their incentive to buy. I document two ways in which society limits the benefits of contracts. First, contracts reduce buyer cheating, thus increasing merchants' profits, if, and only if, the merchant is state‐favored. Buyers' beliefs suggest that the merchants can enforce the contracts if, and only if, the merchant is state‐favored. Second, holding constant whether the pair is state‐favored, contracts only influence buyer choices when the buyer and the merchant belong to two, different, state‐favored ethnic groups. Buyers' choices and beliefs confirm that, in that case, the contracts are expected to be enforceable, but they have no effect on buyers' choices because reputation already governs the incentives to cheat within groups. The findings temper the view of the state as independent from society, offer a rationale for why contracts are not adopted, and nuance the notion of state weakness.