Medicare coverage choice is not neutral: how policy design shapes beneficiary enrollment.

Medicare enrollment has shifted substantially toward Medicare Advantage (MA), rising from 33% in 2016 to over half of beneficiaries by 2025. While often interpreted as reflecting beneficiary preference, Medicare coverage choice is not neutral; policy design systematically advantages MA at the point of enrollment. Medicare's choice architecture concentrates salient financial protections and supplemental benefits within MA while deferring the consequences of managed care restrictions as future considerations, when switching options are limited. We identify 3 domains that create structural asymmetries between MA and Traditional Medicare (TM): affordability and benefit offerings, integrated plan design, and information and marketing. Together, these features make MA's advantages more visible at enrollment, through out-of-pocket caps, supplemental benefits, streamlined coverage, and third-party steering, while TM remains comparatively fragmented. We outline policy options to address these imbalances, including introducing an out-of-pocket cap in TM, expanding benefits, simplifying coverage design, improving decision and support tools, and strengthening oversight of marketing and brokerage practices. Leveling the playing field is not about steering beneficiaries toward TM or MA, but about ensuring that Medicare's growing reliance on enrollee choice rests on a foundation of comparability, transparency, and informed decision-making.