Résumé

How can a social planner use an intervention to disrupt the status quo and recruit cultural evolutionary processes to activate sweeping social change? When conformity and coordination incentives hold, such an intervention operates through at least two channels. It has a direct effect if some people exposed to the intervention change behavior as a result. It also has an indirect effect if some people change behavior because they learn from others. If the indirect effect is large, it dramatically amplifies the direct effect, a possibility that has generated considerable enthusiasm in policy discussions. That said, mundane forms of heterogeneity introduce a number of challenges. Using a mix of models, observational studies, and experimental results, I argue three points. First, some forms of heterogeneity strongly interfere with social change simply because they favor chronic disagreement. Second, even when sweeping social change is feasible, the social planner should often expect a trade-off between the direct and indirect effects of her intervention. Increasing one effect means decreasing the other, and social planners may often lack the information they need to resolve the trade-off effectively. Finally, the link between behavior change and social welfare can be varied and counterintuitive. Intervention strategies that generate persistent disagreement and miscoordination can actually be better than alternative strategies that initiate a complete transition from one norm to another

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