Managing natural-resource allocation and environmental externalities is a challenge. Institutional designs are central when improving water quality for downstream users, for instance, and when reallocating water quantities including for climate adaptation. Views differ on which institutions are best: states; markets; or informal institutions. For transfers of ecosystem services, we compare informal trust-based institutions to enforced contracts, both being institutional types we observe commonly in the field. The trust-based institutions lack binding promises, thus ecosystem-services suppliers are unsure about the compensation they will receive for transferring services to users. We employ decision experiments given the shortcomings of the alternative methods for empirical study of institutions, as well as the limits on theoretical prediction about behaviors under trust. In our bargaining game that decouples equity and efficiency, we find that enforced contracts increased efficiency as well as all measures of equity. This informs the design of institutions to manage transfers of ecosystem services, as equity in surplus sharing is important in of itself and in permitting efficient allocation.

管理自然资源分配和环境外部性是一项挑战。例如，在改善下游用户的水质以及重新分配水量（包括用于气候适应）时，机构设计至关重要。关于哪种机构最好的观点不尽相同：市场; 或非正式机构。对于生态系统服务的转移，我们将非正式的基于信任的机构与强制执行的合同进行了比较，这都是我们在该领域普遍观察到的机构类型。基于信任的机构缺乏有约束力的承诺，因此生态系统服务供应商不确定他们将服务转让给用户时将获得的补偿。鉴于机构研究的替代方法的缺点，我们采用决策实验，以及对信任行为的理论预测的限制。在使公平与效率脱钩的讨价还价博弈中，我们发现，强制执行的合同提高了效率以及所有公平指标。这为管理生态系统服务转移的机构的设计提供了信息，因为盈余分享的公平本身就很重要，而且对有效分配也很重要。