Medicare ACO Statistics: 2026 Report

How Many ACOs Are in the Medicare Shared Savings Program

CMS counts Shared Savings Program ACOs and their assigned beneficiaries on January 1 of each year and adds each year's total earned shared savings once reconciliation is complete. The table below gives those published figures for every year of the program.

Source: CMS, Shared Savings Program Fast Facts, as of January 1, 2026. Data: cms-mssp-fast-facts-2026.csv

• The program had 511 ACOs on January 1, 2026, up from 476 in 2025. That is the most since 2020, and the program's high remains 561 in 2018.
• Assigned beneficiaries rose 12.5% from 11.2 million in 2025 (our calculation from rounded counts). The number of ACOs fell in four of the 13 year-over-year changes, while assigned beneficiaries stayed between 10.4 million and 12.6 million in every year since 2018.
• The 12.6 million people assigned in 2026 are the most in any year of the program. The doctors and hospitals in each ACO earn part of their pay by keeping total Medicare spending for their assigned patients under a yearly target.

CMS approved 134 applications for 2026, made up of 72 new ACOs and 62 renewing or reentering ACOs, according to its February 2026 participation fact sheet. The program's 2026 ACOs include more than 700,000 health care providers and organizations.

Medicare ACO Participation by Initiative in 2026

The Shared Savings Program is the largest of several Medicare programs that hold provider groups accountable for the total cost of care. CMS's 2026 participation fact sheet gives counts for each one.

Source: CMS, 2026 Medicare Accountable Care Organization Initiatives Participation Highlights, February 4, 2026. Data: cms-medicare-aco-initiatives-2026.csv

• CMS estimates 14.3 million Medicare beneficiaries receive care from ACOs in 2026, up from 13.7 million in 2025. CMS puts that increase at 4.4%.
• ACO PC Flex ACOs also take part in the Shared Savings Program. Their 359,720 people are part of its 12.6 million.
• Shared Savings Program beneficiaries make up about 88% of the 14.3 million (our calculation from rounded counts, 12.6 million of 14.3 million). Changes to that program's rules reach far more patients than changes to any of CMS's ACO models.

Shared Savings Program ACOs by Risk Track

ACOs in the Shared Savings Program choose a track that sets how much of their savings they keep and whether they repay losses. From the July to December 2019 period onward, CMS's files show a BASIC track with five levels, A through E, and an ENHANCED track. Levels A and B are one-sided, which means the ACO can earn savings but owes no losses. Levels C, D and E and the ENHANCED track are two-sided. Before July 2019, Track 1 was one-sided and Tracks 1+, 2 and 3 were two-sided. We counted ACOs in each track from CMS's January 1 participation files.

Source: Healthcare Industry Reviews analysis of CMS Shared Savings Program ACO public use files, January 1 of each year. Earlier tracks are Track 1, Track 1+ and Track 2 ACOs still in agreements signed before July 2019. Data: mssp-acos-by-track-jan-1.csv

• The ENHANCED track grew from 80 ACOs in 2020 to 296 in 2026. It holds 57.9% of all 511 ACOs in 2026 (our calculation).
• Two-sided ACOs made up 5.1% of the 433 ACOs in 2016 and 76.3% of the 511 in 2026 (our calculations). BASIC Level E and ENHANCED together account for 378 of the 511, or 74.0% (our calculation).
• Most ACOs now agree to repay Medicare when their patients' spending runs well over the target. For these ACOs, a year of high spending leads to a bill from Medicare.

The one-sided count dropped from 325 ACOs in 2020 to 121 in 2026 (our calculations). Within the BASIC track, the one-sided levels changed size in opposite directions. Level B held 170 ACOs in 2022 and 55 in 2025, while Level A grew from 27 ACOs in 2023 to 82 in 2025 before falling to 55 in 2026. Level E has held between 81 and 125 ACOs in every year since 2022. Levels C and D, the middle steps of the BASIC track, had 12 ACOs between them in 2026, down from 40 in 2022 (our calculations from Table 3).

Shared Savings and Net Savings to Medicare by Performance Year

Each year CMS compares an ACO's spending for its assigned beneficiaries with its benchmark. An ACO that spends less than its benchmark by more than its minimum savings rate and meets the quality standard earns a share of the savings, and a two-sided ACO that spends more than its benchmark by more than its minimum loss rate owes a share of the losses. We summed each ACO's results from CMS's public use files and calculated net savings to Medicare as total savings against benchmarks, minus earned shared savings, plus shared losses owed.

Source: Healthcare Industry Reviews analysis of CMS Shared Savings Program Performance Year Financial and Quality Results public use files, 2012/2013 to 2024. The two 2019 periods cover six months each; see Methodology. Data: mssp-results-by-performance-year.csv

• ACOs earned $4.14 billion in 2024, 33.9% more than the $3.09 billion of 2023 (our calculations, n=476 and n=453 ACOs). Medicare kept 37.7% of what ACOs saved against their benchmarks in 2024 (our calculation, $2.49 billion of $6.61 billion).
• The share of ACOs earning shared savings rose from 23.6% of 220 ACOs in 2012/2013 to 75.6% of 476 in 2024 (our calculations). Medicare's net savings rose in each of the last three reconciled years.
• Through 2016, the shared savings Medicare paid ACOs were larger than the savings ACOs produced, so the program cost Medicare money (our calculations). Since 2017, Medicare has come out ahead in every year.

CMS's PY2024 results fact sheet reports that 75% of 476 ACOs earned performance payments totaling $4.1 billion in 2024. CMS also reports that Medicare saved $2.5 billion relative to benchmarks and that the ACOs earning payments served 80% of the 10.3 million assigned beneficiaries. It puts net per capita savings at $245 in 2024 and $207 in 2023, and gross per capita savings at $651 and $515 (Data: cms-py2024-headline-figures.csv).

Across all 13 performance periods from 2012/2013 to 2024, ACOs earned $19.26 billion in shared savings and owed $100.7 million in losses, and net savings to Medicare came to $11.76 billion (our calculations from Table 4, n=5,476 ACO records). Total savings against benchmarks rose from 3.6% of $120.05 billion in benchmarks in 2022 to 4.7% of $139.75 billion in 2024 (our calculations, n=482 and n=476 ACOs, Data: mssp-benchmark-totals-2022-2024.csv).

The yearly results fall into three periods. From 2012/2013 through 2016, fewer than a third of ACOs earned shared savings in any year. From 2017 through the two 2019 periods, the share earning rose to 56.6% of the 205 ACOs reconciled for July to December 2019. From 2020 through 2024, net savings stayed above $1.6 billion a year, and net savings per assigned person-year rose from $180 in 2020 (n=513) to $246 in 2024 (n=476), all our calculations.

The one break in the recent trend came in 2021, when the share earning fell to 57.7% of 475 ACOs from 67.3% of 513 in 2020 and earned shared savings fell from $2.28 billion to $1.96 billion (our calculations). Both measures rose again in each of the next three years.

Share of ACOs Earning Shared Savings by Track and Risk Level

Higher tracks give an ACO a larger share of savings in exchange for repaying more of any losses. The table below shows how ACOs in each BASIC level and the ENHANCED track did in the three most recent reconciled years.

Source: Healthcare Industry Reviews analysis of CMS Shared Savings Program Performance Year Financial and Quality Results public use files, 2022 to 2024. Shares are our calculations. Data: mssp-results-by-track-2022-2024.csv

• ENHANCED ACOs earned 75.1% of all 2024 shared savings (our calculation, $3.11 billion of $4.14 billion) and produced 46.0% of Medicare's net savings (our calculation, $1.15 billion of $2.49 billion). They served 5,584,151 of the 10,326,340 assigned beneficiaries that year, or 54.1% (our calculation).
• BASIC Level E ACOs returned $293 in net savings per assigned person-year in 2024, against $209 for ENHANCED ACOs (our calculations, n=104 and n=205). BASIC C and D each had five ACOs in 2024, too few to compare with the larger levels.
• An ENHANCED ACO keeps a larger share of what it saves, so less of each dollar saved stays with Medicare. A track that pays ACOs more can return less to Medicare per person-year.

The Level E lead in net savings per person-year also held in the two earlier years. Level E ACOs returned $259 in 2022 (n=98) and $262 in 2023 (n=123), and ENHANCED ACOs returned $137 (n=146) and $170 (n=160), all our calculations.

CMS's CY 2027 Physician Fee Schedule proposed rule fact sheet gives the ENHANCED track a 75% sharing rate and BASIC Level E a 50% rate. In the same fact sheet, CMS writes that evidence suggests Level E ACOs generate higher savings to the Medicare Trust Funds than ENHANCED ACOs, and it proposes raising the Level E sharing rate to 60%.

Grouping the tracks into one-sided and two-sided risk covers more years. Two-sided ACOs earned shared savings more often in every year. Net savings per person-year were higher for two-sided ACOs in 2020 and 2021, within $1 of one-sided ACOs in 2022, and lower than for one-sided ACOs in 2023 and 2024 (our calculations).

Source: Healthcare Industry Reviews analysis of CMS Shared Savings Program Performance Year Financial and Quality Results public use files, risk model field. Data: mssp-results-by-risk-model.csv

• In 2024, 271 of 319 two-sided ACOs earned shared savings, against 89 of 157 one-sided ACOs (our calculations). Two-sided ACOs received 89.6% of the shared savings ACOs earned that year (our calculation, $3.71 billion of $4.14 billion).
• From 2019 to 2024, two-sided ACOs received 76.5% of the shared savings ACOs earned (our calculation, $11.83 billion of $15.47 billion), and they have made up most reconciled ACOs in every year since 2022. The sharing rates CMS sets for the two-sided tracks now govern most of what the program pays ACOs.

Before 2019 the two-sided group was small. It held 22 of 432 reconciled ACOs in 2016, 39 of 472 in 2017 and 95 of 548 in 2018. In each of those years a larger share of two-sided ACOs than one-sided ACOs earned shared savings, at 68.2% against 29.0% in 2016, 51.3% against 32.1% in 2017 and 62.1% against 32.2% in 2018 (our calculations, Data: mssp-results-by-risk-model.csv). One-sided ACOs owed no losses in any year, because their agreements do not require them to repay losses.

Shared Losses Owed by Shared Savings Program ACOs

Only two-sided ACOs can owe shared losses. CMS's results files record which ACOs owed losses and how much. We counted an ACO as owing losses when its earned savings or losses value in the file is below zero, and we summed those values for each year.

Source: Healthcare Industry Reviews analysis of CMS Shared Savings Program Performance Year Financial and Quality Results public use files. Calculated losses are the sum of the generated savings or losses field for ACOs whose earned savings or losses field is zero. Data: mssp-results-by-performance-year.csv, mssp-calculated-losses-2020-2022.csv

• The 16 ACOs owing losses in 2024 were 6 BASIC Level E ACOs owing $10.5 million and 10 ENHANCED ACOs owing $9.5 million (our calculations). Losses owed that year equaled 0.5% of the $4.14 billion ACOs earned (our calculation, n=476 ACOs).
• In 2020, 2021 and 2022, the files show calculated losses for 1, 15 and 15 two-sided ACOs and no ACO owing losses. Each of those ACOs has an entry in the file's disaster adjustment field.
• For most two-sided ACOs, the agreement to repay losses has cost little. In each year outside 2020 to 2022, repayments fell on a small number of ACOs.

Low Revenue and High Revenue ACOs

CMS sorts ACOs into low revenue and high revenue groups by comparing the Medicare Parts A and B fee-for-service revenue of the ACO's participants with total Parts A and B spending for the ACO's assigned beneficiaries. An ACO whose participants' revenue is less than 35% of that spending is low revenue, and the rest are high revenue (42 CFR 425.20). CMS describes low revenue ACOs as typically physician-led or made up of federally qualified health centers and rural health clinics, and high revenue ACOs as typically hospital-led.

The January 1 files carry the revenue flag. Low revenue ACOs grew from 270 in 2020 to 325 in 2026, and high revenue ACOs fell from 247 to 186 over the same years (our counts, n=517 and n=511 ACOs). Low revenue ACOs made up 52.2% of the program in 2020 and 63.6% in 2026 (our calculations).

Source: Healthcare Industry Reviews analysis of CMS Shared Savings Program Performance Year Financial and Quality Results public use files, revenue category field. Data: mssp-results-by-revenue-category.csv

• Low revenue ACOs had a higher share earning shared savings than high revenue ACOs in all five years, by 23.0 percentage points in 2024 (our calculation, n=274 and n=202). They returned 60.7% of 2024's net savings to Medicare (our calculation, $1.51 billion of $2.49 billion).
• CMS reports net per capita savings of $319 for low revenue ACOs and $180 for high revenue ACOs in 2024. It reports $403 for ACOs made up mostly of primary care clinicians and $224 for ACOs with fewer (Data: cms-py2024-headline-figures.csv).
• Low revenue ACOs produced about half of Medicare's net savings from the program in 2020 (our calculation, $932.6 million of $1,861.2 million). By CMS's definition, providers outside a low revenue ACO bill more than 65% of its assigned patients' Parts A and B fee-for-service spending, so most of the spending its savings are measured against is care the ACO does not bill itself (our calculation from 42 CFR 425.20).

Low revenue ACOs had their widest lead in net savings per person-year of any full year in 2018, the first year the results files carry the revenue flag. That year 49.4% of 235 low revenue ACOs earned shared savings, against 28.4% of 313 high revenue ACOs, and net savings per assigned person-year were $185 and $27 (our calculations). High revenue ACOs outnumbered low revenue ACOs in 2018 and have been the smaller group in every reconciled year since 2020.

ACO REACH Participation and Results

ACO REACH is a CMS Innovation Center model for ACOs. It ran as the Global and Professional Direct Contracting (GPDC) Model in 2021 and 2022, was renamed ACO REACH with new rules in 2023, and has its last performance year in 2026. Each entity takes part under a Global arrangement, which shares 100% of savings and losses against its benchmark, or a Professional arrangement, which shares 50%, both subject to risk corridors. CMS publishes a participant file and a results file for each performance year.

Source: Healthcare Industry Reviews analysis of CMS REACH ACOs participant files, 2021 to 2026, one file per performance year. Data: aco-reach-participants-by-year.csv

• REACH had 58 fewer entities in 2026 than at its 2023 high, a drop of 43.9% (our calculation, 74 against 132). New Entrant ACOs fell from 18 in 2021 to 2 in 2026.
• Global arrangements make up 65 of the 74 ACOs in 2026, or 87.8% (our calculation). Professional arrangements fell from 26 entities in 2022 to 9 in 2026.
• Groups have left REACH in each year since 2023, and 2026 is the model's final performance year. Most of the ACOs still in it carry the full risk of the Global arrangement.

Source: Healthcare Industry Reviews analysis of CMS ACO REACH Financial and Quality Results public use files, PY2021 to PY2024. Data: aco-reach-results-by-performance-year.csv

• In 2024, 96 of 115 REACH entities earned shared savings, and 19 owed shared losses (our calculations). Global entities accounted for 98 of the 115 entities and $1.35 billion of the $1.59 billion in 2024 gross savings (our calculations).
• Two Global entities owed $104.8 million and $77.2 million in 2024, and each of the other 14 Global entities with losses owed less than $10 million (our calculations, n=16). Under the Global arrangement, one costly year can leave an ACO owing Medicare tens of millions of dollars.

Aligned beneficiaries in reconciled entities grew from 357,121 in 2021 to 2,510,749 in 2024, and gross savings rose from 1.7% to 4.4% of final benchmarks over the same years (our calculations). In 2024, the 16 Global entities with losses owed $236.9 million in total, against $5.9 million for 3 of the 17 Professional entities (our calculations). CMS estimates that the 74 REACH ACOs in 2026 serve 1.7 million people.

CMS has announced that the Long-term Enhanced ACO Design (LEAD) Model will start in 2027 when ACO REACH ends.

What ACO Statistics Mean for Medicare Providers in 2027

An ACO's earnings depend on CMS's rules for sharing rates and benchmarks as well as on its patients' spending. A change in those rules can raise or lower an ACO's shared savings with no change in its care.

An ACO applying for an agreement that starts January 1, 2027 picks its track during the 2026 application cycle, before CMS finalizes the sharing rates and benchmark changes it proposed in July 2026. CMS has proposed letting those applicants change their track for a limited time after the final rule is published.

An ACO now in REACH needs a new agreement with Medicare to stay in an ACO program in 2027.

The 2025 results are still pending for every Shared Savings Program ACO, and CMS's proposed limit on the benchmark trend would apply to ACOs whose agreements started in 2024, 2025 or 2026. If you run an ACO with an agreement that started in 2024, 2025 or 2026, model your 2025 and 2026 results under both the current benchmark trend and the proposed limit before CMS issues 2025 results.

Data Collection and Methodology

Shared Savings Program results. We downloaded every Performance Year Financial and Quality Results file on data.cms.gov, from the 2012/2013 file to the 2024 file (revised July 17, 2026), with one file for each half of 2019. Each row is one reconciled ACO. Assigned beneficiaries are the assigned beneficiary count field. From 2014, earned shared savings are the sum of positive values in the earned savings or losses field, and losses owed are the sum of negative values in that field, shown as positive amounts. An ACO counts as earning shared savings if that value is above zero and as owing losses if it is below zero. The 2012/2013 file has a separate earned savings field and an owed losses field that stores losses as negative values. For that file we summed the earned savings field as earned shared savings and the absolute value of the owed losses field as losses owed, and counted an ACO as owing losses if its owed losses value is not zero. Total savings against benchmarks are the sum of the benchmark minus expenditures field across all ACOs. Net savings to Medicare are total savings against benchmarks, minus earned shared savings, plus losses owed. Net savings per person-year divide net savings by the sum of assigned beneficiary person-years in the performance-year field. The 2012/2013 file uses its single person-year field, and the two 2019 files cover six months each, so we do not compare their per-person-year values with other years. In 2020, 2021 and 2022, the files record no losses owed by any ACO. The 1, 15 and 15 two-sided ACOs with negative generated savings or losses in those years each have an entry in the file's disaster adjustment field and a zero in the earned savings or losses field. We report their generated amounts separately in Table 7 and leave them out of losses owed. The 2021 file stores numbers with comma separators, which we stripped before summing. Dollar totals are rounded to the nearest $0.1 million and shares to one decimal place, half up, from unrounded values.

Tracks and risk. From 2022 we used the current track field. For 2016 to 2021 we used the current track flags, taking the BASIC level or ENHANCED flag first and the earlier Track 1+, 2 or 3 flags otherwise. Files before 2016 carry a Track 2 flag, and we coded every other ACO in those files as Track 1. One-sided means Track 1 and BASIC Levels A and B, and two-sided means Tracks 1+, 2 and 3, BASIC Levels C, D and E, and ENHANCED. From 2019 the files include CMS's risk model field, which we used directly; for earlier years we applied the track mapping above. Revenue categories use CMS's revenue category field, available from 2018; Table 8 shows 2020 to 2024.

Participation. Counts by track come from the January 1 Accountable Care Organizations files for 2016 to 2026 (one data.cms.gov release per year, each for the start of the performance year). 2014 and 2015 files carry no track fields.

ACO REACH. Participant counts come from the REACH ACOs files for 2021 to 2026 (one data.cms.gov release per year, the April 28, 2021 file for 2021). Entity types and arrangements come from the ACO type and risk arrangement fields in the 2021 file and from the entity type and agreement option fields in later files. The 2021 and 2022 files cover the GPDC Model. Results come from the ACO REACH Financial and Quality Results files for 2021 to 2024. Aligned beneficiaries are the beneficiary count field (aligned beneficiaries field in 2021). Gross savings, final benchmark and shared savings are summed as reported, and an entity counts as having shared savings or shared losses by the sign of its shared savings field. The 2022 results file has 99 entities and the 2022 participant file has 94, and we report each as published. REACH and the Shared Savings Program set benchmarks and pay savings under separate rules, so we do not add the two programs' results together. The REACH and GPDC results files do not publish a net savings to Medicare figure, and we do not calculate one.

Sources

1. Healthcare Industry Reviews, Medicare ACO Study: analysis of 13 CMS Shared Savings Program Performance Year Financial and Quality Results public use files (2012/2013 to 2024, 5,476 ACO records), 11 Shared Savings Program ACO participation files (January 1, 2016 to 2026), and CMS ACO REACH participant and results files (2021 to 2026), conducted October 2026.
2. CMS, Shared Savings Program Fast Facts, as of January 1, 2026 (PDF)
3. CMS, 2026 Medicare Accountable Care Organization Initiatives Participation Highlights, February 4, 2026
4. CMS, Medicare Shared Savings Program Accountable Care Organizations Updated Performance Year 2024 Financial and Quality Results, September 29, 2025 (PDF)
5. CMS, Calendar Year (CY) 2027 Medicare Physician Fee Schedule Proposed Rule (CMS-1848-P), Medicare Shared Savings Program Proposals, July 14, 2026
6. CMS, CMS Redesigns Accountable Care Organization Model to Provide Better Care for People with Traditional Medicare, February 24, 2022
7. CMS Innovation Center, ACO Realizing Equity, Access, and Community Health (REACH) Model FAQs (PDF)
8. eCFR, 42 CFR 425.20, Definitions (Medicare Shared Savings Program)
9. CMS, data.cms.gov, Performance Year Financial and Quality Results (Shared Savings Program dataset, 2012/2013 to 2024)
10. CMS, data.cms.gov, Accountable Care Organizations (Shared Savings Program participation dataset, January 1, 2016 to 2026)
11. CMS, data.cms.gov, ACO REACH Financial and Quality Results (dataset, 2021 to 2024)
12. CMS, data.cms.gov, REACH ACOs (participant dataset, 2021 to 2026)