A letter increased health insurance enrollment by 7.15%.

What was the challenge?

As the open enrollment period for purchasing health insurance through the Federal Health Insurance Marketplace (FHIM) neared its end, many people had visited HealthCare.gov and started an online account, but had not yet selected a plan.

What was the program change?

OES developed eight different letters to assist these individuals with completing their FHIM application before the end of open enrollment. The eight letters contained varied insights, including action language, an implementation intention prompt, a picture, social norm messaging, a pledge, and loss aversion - with the core content held constant across each of the eight letters.

How did the evaluation work?

811,795 individuals who had registered for a HealthCare.gov user account but not yet enrolled in an insurance plan were randomly assigned to be sent one of eight letter variants, or no letter at all.


What was the impact?

By the open enrollment deadline, enrollments increased by 7.15%, amounting to 1,924 marginal enrollments.

Read the Blog: How Much Do Letters Increase Health Insurance Enrollment?

Yokum D, Hopkins DJ, Feher A, Safran E, Peck J. Effectiveness of Behaviorally Informed Letters on Health Insurance Marketplace Enrollment: A Randomized Clinical Trial. JAMA Health Forum. 2022;3(3):e220034. doi:10.1001/jamahealthforum.2022.0034





Project Type

Program Change and Evaluation


Health and Human Services



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