Take me with you! Economic Incentives, Nudging Interventions and Reusable Shopping Bags: A Randomized Controlled Trial

Last registered on January 14, 2021

Pre-Trial

Trial Information

General Information

Title
Take me with you! Economic Incentives, Nudging Interventions and Reusable Shopping Bags: A Randomized Controlled Trial
RCT ID
AEARCTR-0007016
Initial registration date
January 14, 2021

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
January 14, 2021, 11:54 AM EST

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

Locations

Primary Investigator

Affiliation
Zhongnan University of Economics and Law; United Nations Development Program

Other Primary Investigator(s)

PI Affiliation
Ca'Foscari University of Venice

Additional Trial Information

Status
On going
Start date
2019-07-01
End date
2021-02-14
Secondary IDs
Abstract
Little is known about the impact of policy interventions other than taxes and bans to reduce the demand for single use plastic bags. More specifically, the influence of environmental nudges and financial bonuses to curb the single use plastic bag purchase and consumption is largely understudied. To fill this gap, we run an RCT with loyalty card holders of one of the biggest supermarket chains in Yerevan (Armenia) to test and compare interventions based on environmental nudges and financial bonuses. We manipulate the type of the intervention - either a financial bonus or a nudge -, the presence of a reusable bag - either provided for free or not provided -, and the size of the bag - either small or big. Compared with the baseline setting with no intervention, both the financial bonus and the environmental nudge serve as effective policy instruments to reduce disposable bag purchase. Moreover, reusable bags in combination with the environmental nudge or the financial bonus are more effective than the environmental nudge or the financial bonus alone. Finally, the financial bonus is substantially more effective than the environmental nudge, irrespective of the absence/presence of reusable bags.
External Link(s)

Registration Citation

Citation
Antinyan, Armenak and Luca Corazzini. 2021. "Take me with you! Economic Incentives, Nudging Interventions and Reusable Shopping Bags: A Randomized Controlled Trial." AEA RCT Registry. January 14. https://doi.org/10.1257/rct.7016
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Experimental Details

Interventions

Intervention(s)

Intervention Start Date
2020-01-21
Intervention End Date
2020-07-11

Primary Outcomes

Primary Outcomes (end points)
Our experiment aims at testing and comparing the impact of introducing either a financial bonus or an environmental nudge on the purchase of disposable plastic bags. The second aim of the experiment is to test whether interventions that combine differently sized free reusable bags with the environmental nudge or the financial bonus can be more effective as compared with the environmental nudge or the financial bonus alone.

Stemming from the objectives of our experiment, the outcome variable of our analysis is the number of plastic bags purchased by each subject during the experimental time window.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Stemming from our research questions, we designed an experiment consisting of 7 treatments detailed below.

Control group (830 people): Subjects in this group received neither a letter from the supermarket, nor a bag. By comparing the remaining treatments with this group, we are able to check whether the interventions are effective relative to the business as usual setting.

Environmental Nudge (829 people): Subjects in this group received an environmental letter, explaining the harm of the plastic to the environment, animal and human health.

Financial Incentives (830 people): Subjects in this group received a letter, which provided them with financial incentives to purchase fewer plastic bags. More specifically, the subjects were divided into groups of 10. Subjects in each group were competing throughout the experiment. The winner would receive 20,000 AMD (about 40 USD) deposited to her loyalty card. The rules of the competition were as follows:
• Customers received 2 points for spending less than 2000 AMD (around 4 USD) and purchasing no plastic bags;
• Customers received 10 points for spending more than 2000 AMD and purchasing no plastic bags;
• Customers received 0 points if they purchased a plastic bag irrespective of the shopping amount.

Environmental Nudge & Small Bag (830 people): Subjects in this group received the same environmental letter as in the Environmental Nudge treatment and a small tote bag made of non-woven polypropylene.

Environmental Nudge & Big Bag (830 people): Subjects in this group received the same environmental letter as in the Environmental Nudge treatment and a big tote bag.

Financial Incentives & Small Bag (830 people): Subjects in this group received the same letter with financial incentives as in the Financial Incentives treatment and a small tote bag.

Financial Incentives & Big Bag (830 people): Subjects in this group received the same letter with financial incentives as in the Financial Incentives treatment and a big tote bag.
Experimental Design Details
Randomization Method
Randomization was done in office by a computer using STATA 14.
Randomization Unit
Individual level randomization stratified by gender and by the supermarket branch the individual "belongs to."
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
0.
Sample size: planned number of observations
5809 supermarket customers who hold a loyalty card.
Sample size (or number of clusters) by treatment arms
Control group: 830 customers
Environmental Nudge: 829 customers
Financial Incentives: 830 customers
Financial Incentives & Small Bag: 830 customers
Financial Incentives & Big Bag: 830 customers
Environmental Nudge & Small Bag: 830 customers
Environmental Nudge & Big Bag: 830 customers
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB

Institutional Review Boards (IRBs)

IRB Name
Office of Research at Zhongnan University of Economics and Law
IRB Approval Date
2021-01-12
IRB Approval Number
N/A

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials