Testing mailings to increase USPS retirement enrollment and contributions

Glasses on top of document

Glasses on top of document

What was the challenge?

The US Postal Service (USPS) offers a Thrift Savings Plan (TSP) program to help postal employees save for their future. Yet, as many as 86,000 employees do not participate in the program. USPS is interested in ensuring all employees who are eligible and interested are taking advantage of TSP.

What was the program change?

In 2017, we designed a new mailing to encourage TSP enrollment and contributions. The new mailing included a behaviorally-informed cover letter and TSP participation form designed to address each of these barriers to participation. To clarify how to sign up, the cover letter described what TSP was, explained how employees could participate, and provided an example of how an employee might contribute to TSP.

How did the evaluation work?

The new mailings were tested with an individual-level randomized controlled trial. USPS sent the new mailings to 86,899 employees who were eligible for TSP but not yet enrolled in TSP. Of these USPS employees, 42,999 were randomly assigned to receive the new mailing in August 2017 (Wave 1) and 43,900 were randomly assigned to receive the new mailing in September 2017 (Wave 2).

What was the impact?

We were not able to complete the analysis as planned. In cases where data are not available or the evaluation did not provide comparable comparison groups, we do not report results. In this case, outcome data were not available.

Verify the upload date of our Analysis Plan on GitHub.





Project Type

Impact evaluation of program change


Postal Service


Retirement Security


View Analysis Plan (PDF) View Abstract (PDF)