The Persistent Impacts of Norm-Based Messaging and Their Implications for Water Conservation
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Although an increasing number of studies have demonstrated the short-term impacts of behavioral nudges to achieve public policy objectives, less is known about their longer-term impacts. In a randomized experimental design with over 100,000 households, we study the longer-term impacts of a one-time behavioral nudge that aimed to induce voluntary reductions in water use during a drought. Combining technical information, moral suasion, and social comparisons, the nudge has a surprisingly persistent effect. Although its effect size declines by almost 50% after 1 year, it remains detectable and policy-relevant six years later. In fact, the total reduction in water use achieved after the 4-month period targeted by the intervention is larger than the total reduction achieved during the target period. Further analysis suggests that the intervention works through both short-lived behavioral adjustments and longer-lived adjustments to habits or physical capital. Treatment effects are not detectable in homes from which the treated consumers have moved, which provides suggestive evidence that these longer-lived adjustments are mobile rather than incorporated into the housing stock. The persistence of the effect makes the intervention more cost-effective than previously assumed (cost drops by almost 60%). Nevertheless, water utilities may find this persistence undesirable if the nudges are intended to have only a short-run effect on demand during environmental emergencies.
KeywordsLong-term impacts Behavioral channels Other regarding Pro-social Environmental policy Social norms
The authors thank Kathy Nguyen, Herb Richardson, and Kathleen Brown of Cobb County Water System for the water data and Juan Jose Miranda for merging water utility data with tax assessor data.
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