Norm-based feedback on household waste: Large-scale field experiments in two Swedish municipalities

Abstract

We conduct separate randomized controlled trials of norm-based feedback nudges on household waste in two municipalities in western Sweden. Our main treatment presents recipients with accurate, household-specific feedback highly similar to the standard Home Energy Report design, but with residual (unsorted) waste as the object of comparison. We also test a novel ‘dynamic’ norm design informed by psychological research. Post-experimental reductions are on the order of 7-12% in both municipalities, substantially larger than in most previous studies. We estimate that the reduction corresponds to a 30-60% increase in unit-based waste fees. Effect differences between our main treatment and the dynamic-norm treatment are not significant. We find that feedback nudges are highly cost-effective compared to alternative means for reducing household residual waste. However, net social benefits depend on whether existing waste fees internalize the marginal social cost of residual waste. Our results have implications for the usefulness of feedback interventions as well as for unit-based pricing of waste, on which our feedback materials rely.