About one-third of Medicare beneficiaries now rely on Medicare Advantage (MA), the private alternative to traditional Medicare, almost twice as many as did a decade ago. A mainstay of how MA manages costs and quality is through restricting access to specific networks of covered physicians and hospitals. However, we know little about how these limitations actually affect the quality or beneficiary cost of care. This lack of information has two major implications: consumers don’t know what they are buying in MA (in terms of the quality of care they will receive) and policymakers can’t effectively regulate MA markets to optimize access, quality, or costs. The lack of information is driven primarily by the fact that we have little, reliable data about the networks MA provides its patients. Circumventing these challenges, our team has pioneered an innovative approach to characterize the composition of MA physician networks and access on a national scale and over time. This project would apply this approach to high- cost specialists, as well as determine relationships between access and plan quality and costs for beneficiaries. Our broad goal is to understand MA plans’ care delivery though their networks and the resulting impact on quality and costs for MA patients. We previously exploited Part D, the Medicare prescription drug data, to infer networks from prescription events for primary care physicians. The enabling principle is that physicians who prescribe more for enrollees in a plan are more likely to be in-network for that plan than physicians who prescribe less. Though it would be preferable to rely on plan directories for network information, our prior work shows that plan-reported networks have substantial errors. Moreover, they do not capture which physicians are accessible and accepting patients. While there are recently released MA claims data available, they are limited to just three years and are of unknown accuracy. Thus, our approach remains the only known, reliable way to assess MA networks. The proposed project is crucial at this time because the extent to which MA, through establishment of networks, influences the quality of care is unknown to policymakers. Moreover, no specific guidance currently exists as to what beneficiaries gain or give up in exchange for narrower or broader networks in MA. As there are likely tradeoffs across dimensions of quality, premiums, and cost sharing, the findings of this study will be critical for beneficiaries (informing how they choose plans), as well as policymakers, suggesting where greater regulatory scrutiny around network adequacy and quality may be needed.

The percentage of Medicare beneficiaries enrolled in Medicare Advantage has grown significantly in the last decade. However, the relationships among Medicare Advantage physician networks (which plans use to control costs and quality), quality of care, and beneficiary cost are unknown. Using nationally representative, longitudinal data, our study would fill these knowledge gaps, exploring and explaining the tradeoffs across dimensions of network extent, quality, and beneficiary cost.