Testing social norms and feedback provisions for water savings

OECD (2017c)
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The study found that the “average water consumption in Treatment households declined by more than in Control households for each of the three Treatments, although the difference-in-differences is only significant for the Neighbourhood Norms and PlanMaking interventions” (Datta et al., 2015: 16). In general, they also saw that “both control and treatment households’ average monthly water consumption in August-September 2014 was less than their average monthly water consumption in the corresponding season of the previous year. However, the decline in consumption is much larger for households in the Treatment group” (Datta et al., 2015: 16).For the two peer comparison (Neighbourhood and City comparisons) treatment groups, the authors found that “Neighbourhood comparison reduces water use by between 3.5% and 5.6% of control group consumption, but City comparison has no significant effect on water consumption” (Datta et al., 2015: 16). In addition, the results showed that Plan-Making reduces water use by between 3.4% and 5.5%, compared to the water consumption of the control group.Moreover, the study found that Plan-Making appears to be “most effective for lowconsumption households, and Neighbourhood comparison intervention may be most effective for high-consumption households” (Datta et al., 2015: 17).The authors also noted that the average 4 to 5% reduction found across all estimations for the “Neighbourhood Comparison” and the “Plan-Making” treatments can be used for a rough cost-benefit analysis of one the treatments being expended to all the individuallymetered households in the municipality. Based on the monthly average water consumption and the water rates at the time, their results suggest that the monthly water savings (from the household perspective) in monetary terms could be estimated from CRC 1.4 million (USD 2 600) to CRC 2.8 million (USD 5 200).Adding in the additional costs of implementing the treatments (equal to the costs of printing the stickers or postcards, approximately USD 400), the experiment would produce a benefit/cost ratio varying from 6.5 to 13 times. The researchers note that this justifies its expansion to the entire municipality.In terms of water conserved, their results indicate that “on average, in Belén, approximately 6 720 cubic meters of water could be preserved each month. This amount is equivalent to 87 300 baths, 94 080 washing machine loads, 188 000 showers and 222 000 dishwasher loads. Moreover, this decrease in water consumption can forestall the advent of substantial water shortages in Belén’s near future” (Datta et al., 2015: 17).