Low cognitive ability and poor skill with numbers may prevent many from enrolling in Medicare supplemental coverage.

Because traditional Medicare leaves substantial gaps in coverage, many people obtain supplemental coverage to limit their exposure to out-of-pocket costs. However, some Medicare beneficiaries may not be well equipped to navigate the complex supplemental coverage landscape successfully because of their lower cognitive ability or numeracy--that is, the ability to work with numbers. We found that people in the lower third of the cognitive ability and numeracy distributions were at least eleven percentage points less likely than those in the upper third to enroll in a supplemental Medicare insurance plan. This result means that many Medicare beneficiaries do not have the financial protections and other benefits that would be available to them if they were enrolled in a supplemental insurance plan. Our findings suggest that policy makers may want to consider alternatives tailored to these high-need groups, such as enhanced education and enrollment programs, simpler sets of plan choices, or even some type of automatic enrollment with an option to decline coverage.