Abstract
We study how momentum and leadership shape cooperation in repeated public goods provision by adding three new elements. First, we implement a change-based decision mode in which participants adjust their contributions relative to the previous round rather than choosing absolute amounts. This framing increases provision. Second, we generate momentum by varying the returns to the public good across periods. Group contributions follow these induced trends. Yet once behavior converges, outcomes no longer depend on the initial path, suggesting the absence of multiple equilibria. Third, we introduce a leader-follower structure in which one group member each round makes an unconditional contribution, while others specify conditional contributions. Because conditional responses are weaker in the change-based mode, leaders are ineffective in sustaining cooperation beyond the typical patterns.
This is joint work with Sara Constantino.