A Psychological Account of Co-Holding: Why Some Choose to Simultaneously Borrow and Save

Last registered on June 30, 2023


Trial Information

General Information

A Psychological Account of Co-Holding: Why Some Choose to Simultaneously Borrow and Save
Initial registration date
April 22, 2020

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
April 24, 2020, 3:06 PM EDT

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

Last updated
June 30, 2023, 3:59 PM EDT

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



Primary Investigator

University of Chicago Booth School of Business

Other Primary Investigator(s)

PI Affiliation
Stanford University
PI Affiliation
University of Chicago Booth School of Business
PI Affiliation
Stanford University

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
In this experiment, we tested a low-cost intervention where we provided co-holders with a reminder that they could use their assets to pay off their debt. For some, they were also explicitly shown what this could be costing them. The experiment was conducted in partnership with a large retail bank from 17 February 2020 through 18 March 2020. 125,328 customers were selected to take part in this experiment based on a set of pre-specified criteria. In designing the different treatments, we sought to test two hypotheses: Hypothesis 1) Co-holders are unaware that they are co-holding; Hypothesis 2) Co-holders are unaware of the costs of co-holding. To test these hypotheses, we randomized participants into one of three messaging groups. The Control group received no notification about their co-holding behavior. The Notice group received an in-app notification reading: “You usually have at least $500 available to pay your credit card debt. Every $100 you pay off could reduce your interest charges.” The Notice + Cost group received an in-app notification in which the first sentence was identical to the Notice condition and an additional sentence read: “... Every $100 you pay off could reduce your interest charges by about $20 per year. Saving $100 only earns about $1 in interest per year. . . ”. Our primary outcome of interest was the amount customers would pay off their credit card balance. We also specified a series of secondary measures for which we thought we could reasonably detect changes.
External Link(s)

Registration Citation

Batista, Rafael et al. 2023. "A Psychological Account of Co-Holding: Why Some Choose to Simultaneously Borrow and Save." AEA RCT Registry. June 30. https://doi.org/10.1257/rct.5751-2.0
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Credit card repayment amount
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
1. Engagement domain:
a. Indicator for saw T1
b. Indicator for interacted with T1
c. Indicator for saw T2
d. Indicator for interacted with T2
2. Credit card repayment domain:
a. Indictor for repaid more than pre-intervention 3-month average
b. Indicator for repaid more than minimum due
c. Indicator for repaid the full amount due
3. Credit card borrowing domain
a. Revolving balance
b. Indicator for balance higher than pre-intervention 3-month average
c. Interest charges
4. Savings domain
a. Savings balance
b. Indicator for balance higher than pre-intervention 3-month average
c. Interest earnings
5. Net financial benefit domain
a. Net interest (savings interest earnings – credit card interest charges)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We run a randomized controlled trial, messaging people who have revolving credit card debt incurring interest and who have savings over a extended time period. We randomize individuals into one control and two treatment groups. The control group receive no messaging. The first treatment group is shown a message to inform them about their available funds. The second treatment group is shown a message with informs them of their available funds, as well as making salient the cost of co-holding.
Experimental Design Details
Randomization Method
Randomization by app
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
125,328 individuals
Sample size (or number of clusters) by treatment arms
41,776 in control, 41,776 in treatment 1, 41,776 in treatment 2.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
We conducted power analysis to determine minimum detectable effects (MDEs) with α=0.05 and power of 1-β=0.80. We assume the control group sample size is 41,776 and the treatment group is 83,552, pooling together treatment 1 and 2. We run a two-tailed comparison of means, assuming control and treatment groups have the same standard deviations. Based on the analysis, the minimum detectable effect size of credit card repayment amount is $39 on a base of $1,361, or 3% of the mean, and standard deviation of $2,312. Section 4.3 of the pre-analysis plan describes the power analysis in further detail, and table 1 of the pre-analysis plan reports the minimum effect sizes for primary and secondary outcomes. We note when we account for multiple testing, adjusted p-values for a given effect size are roughly twice as large as unadjusted p-values. Any adjustments are made within outcome variable domains (outlined in section 3.3).

Institutional Review Boards (IRBs)

IRB Name
The University of Chicago Social and Behavioral Sciences Institutional Review Board
IRB Approval Date
IRB Approval Number
Analysis Plan

Analysis Plan Documents

Pre-Analysis Plan: Co-Holding

MD5: 9eb4770b7fbf2cc6e0d7878c50d569b2

SHA1: 88457a57a1ada6459ec4dfa1022b5ace9187159e

Uploaded At: July 29, 2020


Post Trial Information

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Is the intervention completed?
Intervention Completion Date
March 18, 2020, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
Final Sample Size: Number of Clusters (Unit of Randomization)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
41424 Control, 41401 Treatment 1, 41426 Treatment 2
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials