Sunk Costs and Exercising

Last registered on February 19, 2025
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Pre-Trial

Trial Information

General Information

Title
Sunk Costs and Exercising
RCT ID
AEARCTR-0011331
Initial registration date
April 25, 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
May 03, 2023, 4:10 PM EDT

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

Last updated
February 19, 2025, 5:49 AM EST

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

Locations

Country
Germany
Region

Primary Investigator

Name
Raphael Epperson
Affiliation
Universtiy of Innsbruck
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Other Primary Investigator(s)

PI Name
Wolfgang Habla
PI Affiliation
Baden-Wuerttemberg Cooperative State University (DHBW)
Contact Investigator
PI Name
Matthias Wibral
PI Affiliation
Maastricht University
Contact Investigator

Additional Trial Information

Status
Completed
Start date
2023-03-01
End date
2024-04-30
Keywords
Behavior, Health
Additional Keywords
Sunk costs, health behavior, exercising
JEL code(s)
D91, I12
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
This project investigates potential sunk-cost effects on exercising behavior by providing a discount on membership fees to randomly selected individuals who recently signed a 12-month or 24-month contract at a fitness chain. Individuals in treatment Early Discount receive a 50% discount on their membership fee for two consecutive months at an early stage of their membership (the 2nd and 3rd, or 3rd and 4th, month of the current membership contract, respectively). To gain a deeper understanding of how individuals mentally account for sunk costs, individuals in treatment Late Discount receive the same 50% discount on their membership fee for two consecutive months, but at a later stage of their membership (in the 8th and 9th, or 9th and 10th, month of the current contract, respectively). At the beginning of the intervention, individuals in both treatment groups receive an email in which they are informed about their discounts. Individuals in the control group also receive an email to control for reminder effects.
External Link(s)

Registration Citation

Citation
Epperson, Raphael, Wolfgang Habla and Matthias Wibral. 2025. "Sunk Costs and Exercising." AEA RCT Registry. February 19. https://doi.org/10.1257/rct.11331-1.1
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
The intervention consists of a discount on the membership fee of randomly selected members, along with an email informing individuals about their discount. The discount is either applied to two early months or two later months of the contract period.
Intervention (Hidden)
Intervention Start Date
2023-04-26
Intervention End Date
2023-12-31

Primary Outcomes

Primary Outcomes (end points)
Average number of weekly gym visits
Primary Outcomes (explanation)
Based on check-in data of members at the fitness chain, we calculate the average number of gym visits per member for given periods of interest (see pre-analysis plan).

Secondary Outcomes

Secondary Outcomes (end points)
Membership renewal at the end of the 12-month contracts
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Each individual is randomly assigned to one of three conditions. Individuals in treatment Early Discount receive a 50% discount on their membership fee for two consecutive months at an early stage of their membership. Individuals in treatment Late Discount receive a 50% discount on their membership fee for two consecutive months at a later stage of their membership. Individuals in the control group do not receive a discount.

At the beginning of the intervention, all individuals receive an email that informs them about some general aspects related to the fitness chain. Members in treatments Early Discount and Late Discount are additionally informed about their discount and its timing.
Experimental Design Details
The sample consists of individuals that purchased either a 12-month or a 24-month contract at the cooperating fitness chain in March 2023. Individuals are excluded from the experiment if (i) they are not at least 18 years old (based on their year of birth), (ii) they share their email address with another member, (iii) they purchased a contract that does not fit the standard contract portfolio offered, or (iv) their contract has a starting date after April 1, 2023. Criterion (ii) and, to some extent, criterion (iii) are implemented by the field partner.

Each individual is randomly assigned to one of three conditions. Individuals in treatment Early Discount receive a 50% discount on their membership fee in May and June 2023. Individuals in treatment Late Discount receive a 50% discount on their membership fee in November and December 2023. Individuals in the control group do not receive a discount.

All participants receive an email on April 26, 2023, that informs them about a current motivational campaign of the fitness chain. Members in treatments Early Discount and Late Discount are additionally informed about their discount and the timing of their discount in this email. Even if individuals in the two discount treatments do not read the email, they should notice the discount on their bank statement (the debit entry occurs at the beginning of each month).

Some participants receive a second email at the end of October 2023. In particular, half of the control group receives an email with general information (related to matters of the fitness chain). Half of the individuals in treatment Late Discount receive an email with the same general information but are additionally reminded of the upcoming discount on their membership fees in November and December.
Randomization Method
The randomization is stratified by two variables: the monthly membership fee of the purchased contract (five categories) and the sex of the individual (male or no male, the second category includes one individual without information). Hence, there are 10 strata. In each stratum, 60% of individuals are assigned to the control group, 20% are assigned to the treatment Early Discount, and 20% are assigned to the treatment Late Discount. If a stratum has a size that cannot be perfectly divided according to these shares (i.e., is not divisible by 5), the number of individuals assigned to a treatment for the remainder is determined by randomly drawing from a vector of five treatment assignments (3 control group, 1 Early Discount, 1 Late Discount) without replacement. The randomization is implemented with R.
Randomization Unit
Individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
3,071 individuals
Sample size: planned number of observations
3,071 individuals
Sample size (or number of clusters) by treatment arms
Control group: ~60%
Treatment Early Discount: ~20%
Treatment Late Discount: ~20%
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
See pre-analysis plan.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Board for Ethical Issues at the University of Innbsruck
IRB Approval Date
2023-04-25
IRB Approval Number
41/2023
Analysis Plan

Analysis Plan Documents

pap.pdf

MD5: 3af1e02a6059d36bddcdf0cc0c63863e

SHA1: fd9164d592612cf6590410cd6fdaae0f18656765

Uploaded At: April 25, 2023

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