It is known that greater social cohesion increases a group’s ability to enforce cooperation. Despite this, defectors often go unpunished, and groups with social structures that are a priori favorable often fail. A critical distinction is required between the structural effect on ability versus willingness to punish. The authors develop a theoretical framework in which variation in a group’s social structure generates a tension between ability and willingness to enforce cooperation. Structures that promote ability to punish also often reduce interest in carrying out sanctions, thus changing collective outcomes. The authors’ empirical analysis involves a well-defined cooperative dilemma: group lending in Sierra Leone. They complement statistical modeling, based on a data set containing 5,487 group repayments, with ethnographic analysis. They find that (1) structural cohesion only increases economic cooperation between borrowers to a point, beyond which unwillingness outweighs increased ability to punish, reducing group repayments, and that (2) groups with disconnected subgroups perform worse on average. Although borrowers are more willing to punish defectors in the out-subgroup, they are unable to do so effectively.

中文翻译：

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能行却不愿执行：集体借贷中的合作困境

众所周知，更大的社会凝聚力会提高一个群体加强合作的能力。尽管如此，叛逃者往往逍遥法外，社会结构先验有利的团体往往失败。对能力的结构性影响与惩罚意愿之间需要一个关键的区别。作者开发了一个理论框架，在该框架中，群体社会结构的变化会在强制合作的能力和意愿之间产生张力。促进惩罚能力的结构通常也会降低执行制裁的兴趣，从而改变集体结果。作者的实证分析涉及一个明确定义的合作困境：塞拉利昂的团体贷款。它们以包含 5,487 组还款的数据集为基础，通过人种学分析对统计建模进行了补充。他们发现（1）结构凝聚力只会将借款人之间的经济合作增加到一定程度，超过这个程度，不愿意超过惩罚能力的增加，减少群体还款，（2）具有断开子群体的群体平均表现更差。尽管借款人更愿意惩罚外部子群体中的叛逃者，但他们无法有效地这样做。