How ACO Conveners Are Changing the Medicare Shared Savings Program (MSSP) Behind the Scenes

Why It Matters

If conveners are systematically aggregating low‑cost clinicians to capture bonuses, Medicare’s shared‑savings model could be exploited, prompting regulators to tighten oversight and redesign incentives.

Key Takeaways

• Third‑party conveners now manage 23% of MSSP beneficiaries.
• Dispersed convenor ACOs grew from 9% to 45% beneficiaries.
• These dispersed ACOs earned $171 per beneficiary, far above peers.
• Quality scores remained similar across convenor and non‑convenor ACOs.
• Evidence suggests conveners cherry‑pick low‑cost clinicians to beat benchmarks.

Summary

The episode examines a new Health Affairs study on third‑party conveners reshaping Medicare’s Shared Savings Program (MSSP). Researchers tracked ACOs from 2012‑2021, finding conveners expanded from 11% to roughly 23% of program beneficiaries and increasingly linked clinicians across distant states.

Key findings show geographically dispersed convenor‑run ACOs rose from 9% to 45% of beneficiaries, while locally‑focused ACOs dwindled to 4%. These dispersed networks captured the highest shared‑savings bonuses—about $171 per beneficiary annually—far outpacing local convenor ACOs ($95) and non‑convenor groups. Despite higher earnings, their quality scores matched those of traditional ACOs.

Dr. Adam Marovitz highlighted that original ACO concepts envisioned local, integrated physician‑hospital networks, not national aggregators. He cited tools like Milleman’s “ACO Builder,” which map low‑cost physicians for network assembly, suggesting strategic cherry‑picking. The study also noted that dispersed convenors’ patients spent roughly $400 less than regional benchmarks, reinforcing the selection hypothesis.

The findings raise policy concerns: conveners may be gaming benchmarks rather than improving care, undermining the MSSP’s intent to align incentives with clinicians. Regulators may need tighter transparency and oversight to ensure ACOs reflect genuine clinical integration rather than cost arbitrage, preserving the program’s cost‑containment goals.

Original Description

Health Affairs Publishing’s Rob Lott speaks to Adam Markovitz of the University of Michigan about his recent paper exploring the growing role of third-party firms in Medicare ACOs ( https://www.healthaffairs.org/doi/10.1377/hlthaff.2025.01574?utm_medium=podcast&utm_source=a+health+podyssey&utm_campaign=june+2026+issue ), highlighting how they have contributed to wider participation and more geographically dispersed networks while raising questions about how these structures relate to shared savings outcomes.

Order the June 2026 issue of Health Affairs ( https://www.pubservice.com/backissue/subbi.aspx?CO=PJ&PC=HR&BI=HRI&utm_medium=podcast&utm_source=A+health+podyssey ).

Sign up for our free Health Affairs newsletters ( https://share.hsforms.com/26dGfZSq8SjaPUznLYa3kfQnnawj ) to stay up to date on health policy news and analysis.

A Health Podyssey

Episode 270

June 23, 2026

★ Episode details: https://share.transistor.fm/s/47fe6e67

★ Additional episodes: https://www.healthaffairs.org/podcasts