Estimated Savings From the Medicare Shared Savings Program.

Importance: The Medicare Shared Savings Program (MSSP) is the largest and most important alternative payment model that has been implemented by the Centers for Medicare & Medicaid Services (CMS). Its budgetary impact to CMS is not well understood. Objective: To evaluate the association between the MSSP and net savings to CMS for performance years 2013 to 2021. Design, Setting, and Participants: The economic evaluation used publicly reported data on the MSSP from April 1, 2012, to December 31, 2021, and estimates extracted from 2 prior studies. Main Outcomes and Measures: Net savings to CMS, calculated as the difference between incentive payments to MSSP accountable care organizations and gross spending reductions. Incentive payments were calculated using the publicly reported data. The association of the MSSP with gross medical spending in traditional Medicare was extracted from 2 prior studies. Spillovers of the MSSP to Medicare Advantage (MA) were estimated by evaluating how gross spending reductions from the MSSP impacted benchmark payments to MA plans. Savings from traditional Medicare and MA were then combined. Results: The MSSP was associated with net losses to traditional Medicare of between $584 million and $1.423 billion over the study period. Savings from MSSP-related reductions to MA benchmarks totaled between $4.480 billion and $4.923 billion. Across traditional Medicare and MA, the MSSP was associated with savings of between $3.057 billion and $4.339 billion. This represents approximately 0.075% of combined spending for traditional Medicare and MA over the study period. Conclusions and Relevance: This economic evaluation found that the MSSP was associated with net losses to traditional Medicare, net savings to MA, and overall net savings to CMS. The total budget impact of the MSSP to CMS was small and continues to be uncertain due to challenges in estimating the effects of the MSSP on gross spending, particularly in recent years.