Leaders’ distributional & efficiency effects in collective responses to policy: Lab-in-field experiments with small-scale gold miners in Colombia

•Small-scale gold mining (SSGM) is a leading economic option for rural frontiers where policies have high transaction costs.•Group compliance measures have lower costs but they invite free-riding in collective responses to incentives.•We employ framed lab experiments in Colombia's Pacific, with 200 small-scale gold miners, to study leaders' impacts.•Communication raises efficiency but not always equity. Leaders’ suggestions influence whether symmetric strategies are used.•Leaders affect the distribution of the costs of group compliance, thus who leads and leadership structures matter for equity. Globally, small-scale gold mining (SSGM) is an important economic option for many rural poor. It involves local uses of shared resources, like common-pool contexts for which self-governance has avoided ‘tragedies of the commons’. Yet even ideal local governance of SSGM is not societally efficient given non-local damages that suggest external interventions for desired shifts. Because transactions costs are high for rewarding reductions in damages on remote mining frontiers, states could gain if rewards based on low-cost, group compliance measures could successfully induce cooperation in response to policy. However, as group-level rewards invite free-riding, such success requires local collective action. Since that guarantees neither efficient coordination nor equitable distributions of net benefits from compliance, we consider the impacts of emergent leaders on local responses to external policy. We employ framed lab experiments with 200 small-scale gold miners in Colombia's Pacific to explore leaders’ impacts on equity and efficiency in collective responses to external incentives. Allowing communication before individual choice, which raises efficiency but not always equity, we can identify emergent leaders of groups’ communications. Leaders raise compliance and affect how its costs are distributed, suggesting access to leadership roles matters.