Tara Hornbeck

Private Medicare plans covered ~54% of eligible US beneficiaries, offering drug coverage, spending caps, dental, and vision, but also tighter networks and prior authorization.
In a ~1M beneficiary study, ~200K developed medical conditions while ~800K did not, and sicker patients became more likely to leave their existing plans.
As health needs grew, beneficiaries increasingly traded extra benefits for broader access, a pattern the analysis described as dynamic adverse selection behavior.
Dementia had the biggest disenrollment effect, and supplemental coverage protections helped beneficiaries exit private plans for traditional coverage, especially when medical complexity was highest.
The broader takeaway: Medicare for All would not erase healthcare trade-offs, because access, utilization controls, spending decisions, and who can say no still matter.