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Question Did spending for patients attributed to accountable care organizations (ACOs) differ from other patients enrolled in Medicare in the first decade of the Medicare Shared Savings Program (MSSP)?
Findings In this difference-in-differences study of more than 8 million patients, ACO formation was associated with a mean differential reduction of $142 (1.2%) in annual per-patient spending over 3 years and $294 (2.4%) over 6 years. Physician-group and small ACOs generated relatively large reductions. Spending changes resulted in $4.1 billion to $8.1 billion in savings to Medicare between 2012 and 2019.
Meaning During the MSSP’s first decade, ACOs generated reductions in spending, with larger effects over time.