Increasing the impact of collective incentives in payments for ecosystem services
通过墨西哥的实地实验，研究了在集体生态系统服务付费项目中，基于额外性（即比基线更好的结果）来支付如何影响群体贡献，并发现群体参与合同设计和协调机制能增强效果。
Collective payments for ecosystem services (PES) programs make payments to groups, conditional on specified aggregate land-management outcomes. Such collective contracting may be well suited to settings with communal land tenure or decision-making. Given that collective contracting does not require costly individual-level information on outcomes, it may also facilitate conditioning on additionality (i.e., conditioning payments upon clearly improved outcomes relative to baseline). Yet collective contracting often suffers from free-riding, which undermines group outcomes and may be exacerbated or ameliorated by PES designs. We study impacts of conditioning on additionality within a number of collective PES designs. We use a framed field-laboratory experiment with participants from a new PES program in Mexico. Because social interactions are critical within collective processes, we assess the impacts from conditioning on additionality given: (1) group participation in contract design, and (2) a group coordination mechanism. Conditioning on above-baseline outcomes raised contributions, particularly among initially lower contributors. Group participation in contract design increased impact, as did the coordination mechanism.