NEW UPDATE: Completed trials may now upload and register supplementary documents (e.g. null results reports, populated pre-analysis plans, or post-trial results reports) in the Post Trial section under Reports, Papers, & Other Materials.
Norm-based feedback on household waste
recycling: a field experiment
Initial registration date
December 03, 2019
December 03, 2019 11:11 AM EST
This section is unavailable to the public. Use the button below
to request access to this information.
University of Gothenburg
Other Primary Investigator(s)
University of Southern Denmark
Additional Trial Information
The last decade has seen a marked upsurge of research into ‘norm-based feedback’ interventions, which aim to reduce the consumption of some resource by providing users with information about their use compared to e.g. neighbors in their community. As far as we are aware, ours is the first study on the effect of providing such feedback within the waste domain. We run separate randomized controlled trials of accurate and household-specific norm-based feedback on residual (unsorted) waste in two municipalities in western Sweden, Partille and Varberg. In total, some 20,000 single-family households participate, about three-quarters of which are located in Varberg. Our main feedback condition, which we term “static” feedback, replicates the by now standard Opower-style norm and involves comparing each household’s own residual waste (in kilograms per person) with an average among roughly 100 nearby households. We also explore differently presented, “dynamic” feedback motivated by psychological evidence that norms focusing on changes in behavior, rather than snapshot pictures of consumption differences within a population, are more effective at reducing use.
Intervention Start Date
Intervention End Date
Primary Outcomes (end points)
Collected residual waste (kgs/person)
Primary Outcomes (explanation)
Secondary Outcomes (end points)
Collected food waste (kgs). If possible, electricity use by households in Varberg
Secondary Outcomes (explanation)
We run separate trials of norm-based feedback on household residual waste (the unsorted waste fraction) in two municipalities in western Sweden, Partille and Varberg. In total, some 20,000 single-family houses participate in these studies, about three-quarters of which are located in Varberg. As in previous studies, the aim of the experiment is to examine whether treated households that receive feedback reduce their generation of residual waste compared to a control group that does not receive feedback.
In both municipalities, households are divided roughly equally into three treatment arms, including a control group. However, the two treatments differ across our participant municipalities.
Experimental Design Details
Random number generator.
Cluster randomization with blocking: three clusters per block. Treatment perfectly correlated within cluster. Each block/cluster is a contiguous set of households.
Was the treatment clustered?
Sample size: planned number of clusters
Partille: 55*3 = 165
Varberg: 172*3 = 516
Sample size: planned number of observations
Due to some households opting out of the study, we expect our actual data set to cover roughly 5,000 in Partille and 15,000 in Varberg.
Sample size (or number of clusters) by treatment arms
Partille: 55 clusters/treatment arm
Varberg: 172 clusters/treatment arm
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Partille MDE: 0.079 kgs residual waste/person (2.378% of data average)
Varberg MDE: 0.050 kgs residual waste/person (1.307% of data average)
This is based on a formula for power calculation with panel data and cluster randomization. For further details on variance components, etc.: see the pre-analysis plan.
INSTITUTIONAL REVIEW BOARDS (IRBs)
Department of Economics Ethics Committee
IRB Approval Date