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Determinants of Public Support for Supply Management: A Randomized Survey Experiment
Last registered on December 06, 2018


Trial Information
General Information
Determinants of Public Support for Supply Management: A Randomized Survey Experiment
Initial registration date
December 04, 2018
Last updated
December 06, 2018 8:27 AM EST
Primary Investigator
University of Manitoba
Other Primary Investigator(s)
PI Affiliation
University of Manitoba
Additional Trial Information
In development
Start date
End date
Secondary IDs
We conduct a survey, with an experimental component, among voting-eligible Canadians to investigate determinants of support for a Canadian food policy called supply management. The experimental component involves randomly assigning respondents to either a control group, or to receive one of three treatments, each of which receives different information on the costs and distributional effects of supply management on consumers. The information treatment on consumer costs is customized to individual recipients’ household characteristics to increase salience. We also randomize the estimated food price increases that result from supply management policies. Detailed information is collected from participants, including household demographics, political preferences, perceptions of other Canadians’ incomes, support for other food policies, and preferences for government redistribution. We investigate correlation between respondent characteristics and support for supply management, and use the experimental structure of our survey to identify causal effects of information treatments on support for supply management. We will estimate interaction effects between treatments and respondent information, including support for redistribution, political affiliation, and views on related food policies.

The survey also includes a section that asks respondents’ preferred level of compensation for farmers, if supply management were to be dismantled. Respondents will be presented with estimated annual costs of compensation (a tax bill) and estimated annual benefits (lower prices).

We also plan a follow-up survey several months after collecting data from the first-round questionnaire. The follow-up will allow us to observe the persistence of treatments from the first round. The follow-up will also include a question that gauges whether a change in respondents’ preferred political party’s position on supply management affects voting behaviour.
External Link(s)
Registration Citation
Cardwell, Ryan and Chad Lawley. 2018. "Determinants of Public Support for Supply Management: A Randomized Survey Experiment." AEA RCT Registry. December 06. https://doi.org/10.1257/rct.3632-1.0.
Former Citation
Cardwell, Ryan, Ryan Cardwell and Chad Lawley. 2018. "Determinants of Public Support for Supply Management: A Randomized Survey Experiment." AEA RCT Registry. December 06. http://www.socialscienceregistry.org/trials/3632/history/38417.
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Experimental Details
Participants are recruited by the polling firm Ekos to be representative of the Canadian population along the dimensions of province and income. The survey will be conducted in English and French. A screening question will allow only those who are eligible to vote in Canada to participate.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
Level of support for supply management, effect of information on support for supply management.
Primary Outcomes (explanation)
Support for supply management is captured through a referendum question on whether to maintain or dismantle supply management. Effect of information on support for supply management is identified by randomising treatments across participants.
Secondary Outcomes
Secondary Outcomes (end points)
Level of support for different compensation options for farmers if supply management were dismantled. Assess the extent to which changes in stated support for supply management by an individuals preferred political party will affect that individual’s support for the political party.
Secondary Outcomes (explanation)
Participants will be presented with a table of options of compensation levels for farmers if supply management were to be dismantled. One preferred choice will be selected. Table will include estimated costs and benefits for participants. Cost and benefit information in this table are customised based on respondents’ estimated expenditures on supply managed products, and on estimated price effects after dismantling.

A follow up survey will be conducted. This survey will be similar to the first round survey is most respects. A new question in the follow up survey will ask participants to suppose that their preferred political party (based on their answer to a previous question) has changed their position on supply management. Respondents will then be asked to indicate which party they would be most likely to vote for in a federal election.
Experimental Design
Experimental Design
Our survey instrument collects detailed information on respondents, including household characteristics, opinions on food policies, views on income redistribution, and political preference.
Respondents are randomly assigned to one of four groups in the first round of the survey:
1. Control group – no information treatment
2. Treatment group 1 – customised information on household costs due to supply management
3. Treatment group 2 – information on distributional effects of supply management on consumers
4. Treatment group 3 – combined information from previous two treatments.
Experimental Design Details
Randomization Method
Respondents are randomly assigned to one of four groups using the Voxco software platform.
Randomization Unit
Not clustered.
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
Sample size: planned number of observations
5,000 respondents
Sample size (or number of clusters) by treatment arms
1,250 respondents in the control group and each of the three treatment groups.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
University of Manitoba Joint-Faculty Research Ethics Board
IRB Approval Date
IRB Approval Number
Protocol #J2018:060 (HS20555)
Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)