Medicare Advantage Enrollment and Beneficiary Risk Scores: Difference-in-Differences Analyses Show Increases for All Enrollees On Account of Market-Wide Changes.

Medicare adjusts payments to Medicare Advantage (MA) insurers using risk scores that summarize the relationship between fee-for-service (FFS) Medicare spending and beneficiaries' demographic characteristics and documented health conditions. Research shows that MA insurers have increasingly documented conditions more thoroughly than traditional Medicare-resulting in higher payments to insurers-but little is known about what factors contribute to diverging risk scores. We apportion that divergence between market-wide increases and increases that vary with length of MA enrollment.