The Persistence of Treatment Effects with Norm-Based Policy Instruments: Evidence from a Randomized Environmental Policy Experiment

Policymakers increasingly use norm-based messages to promote conservation efforts. Despite the apparent success of such strategies, empirical analyses have thus far focused exclusively on short-run effects. From a policy perspective, however, whether and how such strategies influence behavior in the long-run is of equal interest. We partner with a metropolitan water utility to implement a natural field experiment examining the effect of such messages on longer-run patterns of water use. Empirical results are striking. While appeals to pro-social preferences affect short-run patterns of water use, only messages augmented with social comparisons have a lasting impact on water demand.