Time Preferences and Food Choice

Last registered on September 15, 2023

Pre-Trial

Trial Information

General Information

Title
Time Preferences and Food Choice
RCT ID
AEARCTR-0012106
Initial registration date
September 12, 2023

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
September 15, 2023, 8:58 AM EDT

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

Locations

Region

Primary Investigator

Affiliation
University of Oregon

Other Primary Investigator(s)

PI Affiliation
University of Chicago
PI Affiliation
University of Arkansas

Additional Trial Information

Status
Completed
Start date
2018-03-01
End date
2019-05-15
Secondary IDs
AsPredicted #9427
Prior work
This trial is based on or builds upon one or more prior RCTs.
Abstract
This paper uses data from an RCT that was pre-registered with AsPredicted.org and published in ReStat. Some parts of that pre-registration deal with analysis that didn't make it into that paper, but appear in a new paper that we intend to submit to AEA journals. The relevant pre-registration remains the AsPredicted document from before the study was run.

Healthy food choices are a canonical example used to illustrate the importance of time preferences in behavioral economics. However, the literature lacks a direct demonstration that they are well-predicted by incentivized time preference measures. We offer direct evidence by combining a novel, two-question, incentivized time preference measurement with data from a field experiment that includes grocery purchases and consumption. Our present-focus measure is highly predictive of food choice, capturing a number of behaviors consistent with self-control problems, which provides direct evidence for the common assumption that important aspects of nutrition are driven by time preferences.

Registration Citation

Citation
Brownback, Andy, Alex Imas and Michael Kuhn. 2023. "Time Preferences and Food Choice." AEA RCT Registry. September 15. https://doi.org/10.1257/rct.12106-1.0
Sponsors & Partners

Sponsors

Experimental Details

Interventions

Intervention(s)
Subjects in our study will be given discounts on grocery purchases. They can choose between discounts on fruits & vegetables (healthy purchases) and discounts on baked goods (unhealthy purchases). We will experimentally test the impact of making the subsidy choice A) with a waiting period—a delay between learning about the choice and the ability to making the choice, B) with commitment—where binding choices are made before a shopping trip takes place, both relative to individuals making the choice without a waiting period or commitment.

We will also experimentally vary whether individuals encounter a choice at all: some will be unconditionally given a subsidy on fruits & vegetables. We will compare how much of the subsidy is used between those who choose their own subsidy and those who do not. Our hypothesis is that individuals who choose their own subsidy will use more of it.

We will also explore the impact of time preferences (as measured in the baseline survey) on the food choices of our subjects. We hypothesize that more impatient subjects will be more likely to choose the subsidy for immediately satisfying, but unhealthy foods, and that they will be more affected by the waiting period and commitment treatments.
Intervention Start Date
2018-03-08
Intervention End Date
2019-05-01

Primary Outcomes

Primary Outcomes (end points)
Food subsidy choice is binary: = 1 if the choice is for fruits & vegetables, = 0 if the choice is for baked goods. Subsidy use is the value of goods purchased within the category covered by the subsidy. We will report this both as a dollar amount and as a fraction of overall food spending. We will analyze the overall "nutrition" of a shopping trip, where nutrition is the ratio of spending on fruits & vegetables and meat & dairy to spending on baked goods, snacks and sweetened beverages. Our baseline and endline surveys capture behavior and welfare changes. Behavior changes are captured by shopping receipts from before and after the study. We will analyze these as stated above. Both surveys contain single-day food consumption diaries. We will analyze changes in the food diaries along 3 dimensions: (1) are there fruits & vegetables, (2) the ratio of fruits & vegetables to other goods, (3) overall nutrition. Welfare changes are captured with direct questions. We ask 2 questions on food sufficiency: 1)Which of these statements best describes the food eaten in your food household in the last 30 days? A: “Enough of the kinds of food we want to eat;” “Enough, but not always the kinds of food we want to eat;” “Sometimes not enough to eat;” “Often not enough to eat” 2) In the last 30 days, did you ever worry about whether your food would run out before you got money to buy more? A: “Almost always;” “Most of the time;” “About half of the time;” “Some of the time;” “Almost never.” We ask two questions on healthy foods: 1) In the last 30 days, did you ever feel like your food household couldn't afford to eat well-balanced (healthy) meals because you couldn't afford it? (same answers as before) 2) Do you think your food household eats the right amount of fruits and vegetables? A: “Yes, we eat the right amount;” “No, we should eat more;” “No, we should eat less.” We ask a question on physical health: How would you rate your physical health status? A: “Excellent;” “Very good;” “Good;” “Fair;” “Poor.” We ask a question on cognitive well-being: Thinking about the past couple weeks, do you find that you have difficulty maintaining energy, focus or attention? A: “Almost always;” “Most of the time;” “About half of the time;” “Some of the time;” “Almost never.” We collect self-reports of behavior change: Did you change the foods you ate because of the study (check all that apply)? A: “I ate more fruits & vegetables;” “I ate fewer fruits & vegetables;” “I ate more baked goods;” “I ate fewer baked goods.” We will analyze the within-individual changes in these variables: = 0 if the measure stayed the same, = 1 if the measure improved, = -1 if the measure worsened.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
There are 5 conditions each varying the nature and existence of food subsidies. Subjects are assigned using block-randomization following the baseline survey. Randomization is blocked based on participation in SNAP, and a stated desire to eat more fruits & vegetables, to ensure these characteristics are balanced across treatments.

Control condition: Subjects do not receive food subsidies. They participate in the baseline and endline and their shopping trips in between are observed. This group is used the show a lack of time trends between baseline and endline (or to adjust the main results if there are time trends) and the lack of experimenter observation effects (or to adjust the main results if there are experimenter observation effects).

No-choice condition: Subjects receive a 30% subsidy on fruits & vegetables (up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys.

Immediate condition: Subjects choose between a 30% subsidy on fruits & vegetables or a 30% subsidy on baked good (both up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys. They make this choice in the grocery store during their shopping trip.

Commitment condition: Subjects choose between a 30% subsidy on fruits & vegetables or a 30% subsidy on baked good (both up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys. They make this binding choice between 4 and 48 hours prior to their grocery shopping trip.

Waiting period condition: Subjects choose between a 30% subsidy on fruits & vegetables or a 30% subsidy on baked good (both up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys. They make this choice in the grocery store during their shopping trip but are notified and reminded of this upcoming choice 4 to 48 hours prior to their grocery shopping trip.
Experimental Design Details
There are 5 conditions each varying the nature and existence of food subsidies. Subjects are assigned using block-randomization following the baseline survey. Randomization is blocked based on participation in SNAP, and a stated desire to eat more fruits & vegetables, to ensure these characteristics are balanced across treatments.

Control condition: Subjects do not receive food subsidies. They participate in the baseline and endline and their shopping trips in between are observed. This group is used the show a lack of time trends between baseline and endline (or to adjust the main results if there are time trends) and the lack of experimenter observation effects (or to adjust the main results if there are experimenter observation effects).

No-choice condition: Subjects receive a 30% subsidy on fruits & vegetables (up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys.

Immediate condition: Subjects choose between a 30% subsidy on fruits & vegetables or a 30% subsidy on baked good (both up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys. They make this choice in the grocery store during their shopping trip.

Commitment condition: Subjects choose between a 30% subsidy on fruits & vegetables or a 30% subsidy on baked good (both up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys. They make this binding choice between 4 and 48 hours prior to their grocery shopping trip.

Waiting period condition: Subjects choose between a 30% subsidy on fruits & vegetables or a 30% subsidy on baked good (both up to a $10 value) in 4 grocery shopping trips between the baseline and endline surveys. They make this choice in the grocery store during their shopping trip but are notified and reminded of this upcoming choice 4 to 48 hours prior to their grocery shopping trip.
Randomization Method
Computer
Randomization Unit
Individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
Our goal is for 750 subjects (150 in each of the 5 treatments) to complete the baseline survey. We will screen substantially more subjects and invite 750 eligible to complete the baseline. If individuals fail to complete the baseline, we will backfill with more eligible subjects. We will backfill subjects to ensure that 750 subjects complete the baseline and each treatment has 150 subjects. Since subjects don’t learn of their treatment until the week 1 survey, we do not have to worry about attrition based on treatment assignment at this point.
Sample size: planned number of observations
Our goal is for 750 subjects (150 in each of the 5 treatments) to complete the baseline survey. We will screen substantially more subjects and invite 750 eligible to complete the baseline. If individuals fail to complete the baseline, we will backfill with more eligible subjects. We will backfill subjects to ensure that 750 subjects complete the baseline and each treatment has 150 subjects. Since subjects don’t learn of their treatment until the week 1 survey, we do not have to worry about attrition based on treatment assignment at this point.
Sample size (or number of clusters) by treatment arms
Our goal is for 750 subjects (150 in each of the 5 treatments) to complete the baseline survey. We will screen substantially more subjects and invite 750 eligible to complete the baseline. If individuals fail to complete the baseline, we will backfill with more eligible subjects. We will backfill subjects to ensure that 750 subjects complete the baseline and each treatment has 150 subjects. Since subjects don’t learn of their treatment until the week 1 survey, we do not have to worry about attrition based on treatment assignment at this point.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB

Institutional Review Boards (IRBs)

IRB Name
University of Arkansas Institutional Review Board
IRB Approval Date
2017-07-24
IRB Approval Number
17-06-751

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
Yes
Intervention Completion Date
April 19, 2019, 12:00 +00:00
Data Collection Complete
Yes
Data Collection Completion Date
April 30, 2019, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
1102 in baseline, 805 shopping surveys
Was attrition correlated with treatment status?
Yes
Final Sample Size: Total Number of Observations
Depends on how data are used: 2,767 in shopping surveys
Final Sample Size (or Number of Clusters) by Treatment Arms
Reports, Papers & Other Materials

Relevant Paper(s)

Abstract
We conduct a field experiment with low-income shoppers to study how behavioral interventions can improve the effectiveness of healthy food subsidies. Our unique design enables us to deliver subsidies both before and during grocery shopping. We examine the effects of two non-restrictive changes to the choice environment: giving shoppers agency over the subsidy they receive and introducing a waiting period before a subsidized shopping trip to prompt deliberation about upcoming purchases. These interventions increase healthy food spending by 61% more than a healthy food subsidy alone, resulting in 199% greater healthy spending than in our unsubsidized control group.
Citation
Brownback, A., Imas, A., and Kuhn, M.A. 2023. "Behavioral Food Subsidies," Review of Economics and Statistics, forthcoming.

Reports & Other Materials