Interactions of behavioral interventions across pro-environmental domains: A natural field experiment

Despite the proliferation of behavioral nudges across pro-environmental domains, it remains unclear whether and how these interventions interact. We study nudge interactions through a two-year natural field experiment, in which two Home Report-type social-comparison interventions—targeting household waste sorting (HWSR) and water conservation (HWR), respectively—were implemented either independently or jointly. The HWSR improved waste sorting regardless of whether the HWR was also applied. However, while the HWR reduced water consumption when implemented alone, it became ineffective when combined with the HWSR. This crowding-out effect eliminates the welfare gains from the HWR under pre-existing water tariffs that weakly internalize the environmental costs of water use. Additional evidence suggests that crowding out was most pronounced in communities with high social capital and without monetary rewards for waste sorting, and that the HWSR strengthened recipients’ moral-normative beliefs in these communities. We discuss potential crowding-out mechanisms related to attention and preferences.