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How Much to Save? Decision Costs and Retirement Plan Participation
Last registered on August 20, 2019


Trial Information
General Information
How Much to Save? Decision Costs and Retirement Plan Participation
Initial registration date
August 15, 2019
Last updated
August 20, 2019 10:55 AM EDT
Primary Investigator
United States Military Academy
Other Primary Investigator(s)
PI Affiliation
William and Mary
PI Affiliation
Stanford University
PI Affiliation
New York University
Additional Trial Information
Start date
End date
Secondary IDs
Deciding how much to save for retirement can be complicated. Drawing on a field experiment conducted with the Department of Defense, we study whether such complexity depresses participation in an employer-sponsored retirement saving plan. We find that simplifying one dimension of the enrollment decision, by highlighting a potential rate at which non-participants might contribute, increases participation in the plan. Similar communications that did not include a highlighted rate yielded smaller effects. The results highlight how reducing complexity on the intensive margin of a decision (how much to contribute) can spill over into extensive margin behavior (whether to contribute at all).
External Link(s)
Registration Citation
Goldin, Jacob et al. 2019. "How Much to Save? Decision Costs and Retirement Plan Participation." AEA RCT Registry. August 20. https://doi.org/10.1257/rct.4588-1.0.
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Experimental Details
In this study, we investigate whether the complexity of the retirement savings decision depresses participation in retirement savings plans. We analyze the results of a field experiment conducted by the U.S. Department of Defense (DOD). The experiment involved the roughly 300,000 active duty U.S. Army servicemembers who were not enrolled in the Thrift Savings Plan(TSP), the defined contribution portion of the retirement plan the U.S. government offers to its employees. The DOD randomly assigned a subset of these individuals to receive a one-time email that provided information about how to enroll in the TSP and encouraged them to join. For some randomly assigned individuals, the email also attempted to reduce the complexity of the savings decision by highlighting a specific rate (i.e., 1%, 2%, ...8%) at which the individual could choose to contribute. A final group of individuals were randomly assigned to a control group that did not receive any email.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
(1) Participation in Thrift Savings Plan (TSP)
(2) Percent of income contributed
(3) Total savings
(4) Indicator for contributing specific rates (i.e. 1, 2,...,8%)
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Types of TSP funds
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
In January 2016, the Department of Defense (DOD) randomly assigned all active-duty Armed Service servicemembers who had not contributed to a TSP account (Including approximately 300,000 Army servicemembers) to be assigned to one of the following 10 treatment groups:
1) Control group (no intervention)
2) Receive a one-time email that provided information about how to enroll in the TSP and encouraged them to join.
3-10) Receive a one-time email that provided information about how to enroll in the TSP and encouraged them to join and the following the message: "Many servicemembers like you start by contributing at least X% of their basic pay into a Traditional or Roth TSP account,", where X% varied between 1%, 2,%, 3%, 4%, 5%, 6%, 7%, and 8% for treatment groups 3-10.
Experimental Design Details
Randomization Method
Last 2 digits of SSN
Randomization Unit
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
291,552 Army Servicemembers
Sample size: planned number of observations
291,552 Army Servicemembers
Sample size (or number of clusters) by treatment arms
291,552 Army Servicemembers
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
US Military Academy Human Research Protection Program
IRB Approval Date
IRB Approval Number
18-054 Patterson-Skimmyhorn-Goldin-Homonoff
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)