Norm-based feedback on household waste recycling: a field experiment

Last registered on November 01, 2023


Trial Information

General Information

Norm-based feedback on household waste recycling: a field experiment
Initial registration date
December 03, 2019

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
December 03, 2019, 11:11 AM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
November 01, 2023, 10:10 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.


Primary Investigator

University of Gothenburg

Other Primary Investigator(s)

PI Affiliation
University of Southern Denmark

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
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.
External Link(s)

Registration Citation

Ek, Claes and Magnus Söderberg. 2023. "Norm-based feedback on household waste recycling: a field experiment." AEA RCT Registry. November 01.
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Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Collected residual waste (kgs/person)
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Collected food waste (kgs). If possible, electricity use by households in Varberg
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
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
Randomization Method
Random number generator.
Randomization Unit
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?

Experiment Characteristics

Sample size: planned number of clusters
Partille: 55*3 = 165
Varberg: 172*3 = 516
Sample size: planned number of observations
Partille: 5,756 Varberg: 15,723 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)

IRB Name
Department of Economics Ethics Committee
IRB Approval Date
IRB Approval Number
Analysis Plan

Analysis Plan Documents

Pre-analysis plan

MD5: a401b4d173bd9e50f34c544b11bf04d7

SHA1: b61bfe4c538dd70d37caa1a3a135c2e685decd27

Uploaded At: December 03, 2019


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Intervention Completion Date
November 24, 2019, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
November 22, 2020, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
Partille: 165 clusters.
Varberg: 516 clusters
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Partille: 5,519 addresses.
Varberg: 14,935 addresses.
Final Sample Size (or Number of Clusters) by Treatment Arms
Partille: Control (1,837 addresses), Monthly feedback (1,838), Quarterly feedback (1,844) Varberg: Control (4,971 addresses), Standard HER (4,961), Short-run dynamic (5,003
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials