Offices of Physicians (except Mental Health Specialists) — U.S. Industry Primer

NAICS 2022 code 621111

1. Overview

This is the business of doctors seeing patients in the outpatient setting: primary-care practices, specialist offices, and multispecialty medical groups run by doctors of medicine (MD) or osteopathic medicine (DO). It is one of the largest single industries in the U.S. economy by employment, and it is the front door to roughly a fifth of all national health spending [6].

The industry matters to any investor — public or private — for the same reason it is hard to own: the money flows are enormous, recurring, and demographically tailwinded (an aging population buys more physician care every year), yet the ownership is scattered across tens of thousands of small firms and, increasingly, hospitals and insurers. It is extremely fragmented — the four largest firms hold only about 6.2% of national receipts [2] — and most of it is owned by the doctors themselves or by health systems, not by tradable companies. There is no large-cap "pure physician office" stock.

• Public-market ways in are indirect and narrow: a handful of "physician-enablement" and value-based-care companies (Privia Health, agilon health, Astrana Health, P3 Health Partners), plus diversified giants where employed-physician groups are one segment (UnitedHealth's Optum, CVS Health's Oak Street, Humana's CenterWell, Amazon's One Medical).
• Private-market ways in are where most of the action is: buying or partnering into practices directly, private-equity-backed specialty roll-ups run through management-services structures, and the real estate under the practices (medical office buildings).

Editorial view. Demand should stay durable, but returns depend far less on raw patient volume than on physician retention, payer contracts, billing performance, local market power, and regulatory discipline.

2. What it is and how it's structured

Scope. NAICS 621111 covers establishments of licensed MDs/DOs primarily engaged in the independent practice of general or specialized medicine or surgery — family medicine, internal medicine, pediatrics, cardiology, orthopedics, dermatology, gastroenterology, ophthalmology, oncology, anesthesiology, general surgery, and so on. It includes solo practices, group practices, and physicians practicing within health-maintenance-organization (HMO) medical centers or freestanding clinics [3].

What it excludes (named adjacent NAICS codes) [3]:

• 621112 Offices of Physicians, Mental Health Specialists — psychiatrists and psychoanalysts are broken out separately.
• 621210 / 621310 / 621320 / 621330 / 621340 / 621391 — offices of dentists, chiropractors, optometrists, non-physician mental-health practitioners, therapists (physical/occupational/speech), and podiatrists.
• 6214 Outpatient Care Centers — including HMO medical centers (621491), freestanding ambulatory-surgical and emergency centers (621493), kidney-dialysis centers (621492), and all-other outpatient clinics (621498).
• 6215 medical and diagnostic laboratories.
• 6216 home-health care services.
• 622 Hospitals — this exclusion matters enormously (see Section 3).

Ownership mix. The American Medical Association's (AMA) 2024 physician-level benchmark puts doctors at roughly: private practice 42.2% (down from 60.1% in 2012), hospital- or health-system-owned practices 34.5%, and private equity owned or invested in about 6.5%, with the balance in other arrangements [7]. These are physician-level survey shares, not establishment counts, and should not be added up as market shares. The direction of travel is one-way: the share of doctors in independent private practice has fallen almost every year and is now below half [7]. Ownership varies sharply by specialty — private practice is still the majority in fields like ophthalmology and orthopedics but well under a third in others such as cardiology [7].

The MSO structure. Because many states restrict who may own a medical practice (Section 7), outside capital typically enters through a management-services organization (MSO) that owns the business assets — billing, information technology (IT), staffing, purchasing, real estate, administration — while a physician-owned professional entity retains the clinical license and clinical control [14]. In a private deal the legal owner of the clinical practice, the owner of the MSO, and the holder of the economic rights can all be different parties.

3. How big it is

Federal business statistics for NAICS 621111:

Read these carefully. The figures mix reference years (2022 receipts/firms vs. 2023 employment/payroll) and are not a single-period snapshot. Receipts are gross revenue, not profit. The 2.7 million "employees" counts everyone on office payrolls — nurses, medical assistants, front-desk and billing staff — not just physicians. For clinician scale, the U.S. had about 1,032,365 active physicians in 2024, of whom roughly 866,000 were in direct patient care [8].

Two undercount caveats.

1. Employer-only view. County Business Patterns and the Economic Census concentration tables count establishments with paid employees and exclude most government-run operations [1][2]. Nonemployer (self-employed, no-payroll) physicians are covered by a separate Census program, and our supplied file has no 621111 nonemployer add-on — so no total for the full universe of tiny, self-employed, or government physician operations is stated here [4].
2. Structural migration. The 621111 line systematically understates total physician-delivered care. As hospitals and health systems buy up practices, the revenue those doctors generate is increasingly classified under hospitals (NAICS 622) or outpatient care centers (NAICS 6214), not under 621111. That is why the industry's $630.2 billion of office receipts [2] sits far below the $978 billion the federal health accounts attribute to "physician and clinical services" nationally in 2023 [6]. The office line is shrinking as a share of physician economics even as physician work grows, because the work is migrating into other NAICS buckets.

On any standard reading the industry is barely concentrated at all: an HHI of 18.5 is effectively zero on the 0–10,000 antitrust scale (regulators treat anything below 1,500 as "unconcentrated"). The real concentration is local, not national (Section 8).

4. The investable universe

There is no clean, pure-play public index for this industry. Public-company exposure is almost always mixed with insurance, pharmacy, hospitals, medical distribution, technology, or other health-care services. Market-cap and membership figures below are approximate, mid-2026, and move around a lot — several of these are small, volatile stocks [35].

Public "enablers" / medical groups (closest to a direct physician-office bet):

Diversified owners where physician offices are one segment (much larger companies, small % of revenue):

Specialty MSO / facility exposure inside a broader business:

Major private and non-tradable owners (where most physician-office economics actually sits):

• Kaiser Permanente's Permanente Medical Groups — more than 25,000 physicians, the largest medical group in the U.S. [20].
• Hospital and academic health systems — now employ over a third of all physicians [7], often adding facility fees after acquisition.
• Private-equity-backed specialty platforms — roll-ups in dermatology, gastroenterology, ophthalmology, anesthesia, orthopedics and urology, held via MSO structures. Prominent examples: ChenMed (family-owned senior primary care), TeamHealth (Blackstone-owned physician services), U.S. Anesthesia Partners (Welsh, Carson, Anderson & Stowe-backed; the antitrust flashpoint of Section 8), and U.S. Dermatology Partners [34].
• Physician-owned partnerships — the 138,120-firm long tail [2], and the pool from which most acquisitions are made.

Bottom line for a public-market investor: you cannot buy "the industry." You can buy a levered bet on value-based-care execution (the enablers), a small slice of employed-physician care inside a health-insurance giant, or indirect specialty exposure through a distributor or surgical operator. In private transactions, remember that the legal owner of the clinical practice, the owner of the MSO, and the holder of the economic rights may all be different entities.

5. How the money works

Physician offices are, at core, fee-for-service (FFS) billing shops — with a growing overlay of capitation.

Fee-for-service (still most revenue). Each patient encounter is coded (using Current Procedural Terminology, or CPT, codes) and billed to a payer. Medicare's Physician Fee Schedule sets the benchmark: every service carries relative value units (RVUs) for physician work, practice expense, and malpractice, multiplied by a national dollar conversion factor ($32.35 in 2025) [11]. Commercial insurers typically pay some multiple of Medicare rates; Medicaid usually pays less. Revenue is roughly visit/procedure volume × payer mix × contracted rate. The unit-economics levers that matter:

• Physician productivity — work RVUs (wRVUs) per full-time doctor.
• Payer mix — the split among commercial (best-paying), Medicare, Medicaid (worst-paying), and self-pay. A commercial-heavy practice earns far more per RVU than a Medicaid-heavy one.
• Ancillary revenue — in-office labs, imaging, physical therapy, procedures, and physician-administered drugs ("buy-and-bill") carry higher margins than office visits; cosmetic, concierge, and cash-pay services add more.
• Overhead ratio — staff, rent, supplies, and billing typically eat 50%+ of collections; physician compensation is the single largest cost.
• Site of service — hospital-owned practices can add a facility fee on top of the professional fee, which is why the same visit often costs more once a hospital buys the practice.

Owner economics. In a physician-owned group, partners split the residual profit after overhead and their own base pay — the practice is their income and their equity. Medical Group Management Association (MGMA) benchmarking shows physician-owned groups collect meaningfully more per provider than hospital-owned ones (a six-figure gap in primary care), but they also absorb all cost inflation directly [23]. Office businesses are far less capital-intensive than hospitals, but labor is hard to substitute and site overhead stays fixed when appointment volume falls.

Value-based care and capitation (the growth model, and the public companies' model). Instead of billing per service, the group takes a fixed per-member-per-month (PMPM) payment — often from a Medicare Advantage (MA) plan — to cover a patient's care. Profit is the PMPM minus the cost of that patient's medical care; the key ratio is the medical loss ratio (MLR) or medical-cost ratio, the share of premium spent on care. Keep patients healthy and out of the hospital and the spread is yours (plus "shared savings"); guess the cost wrong and you lose money fast. This is exactly how agilon, Privia's risk book, Astrana, and P3 make (or lose) money — and why their earnings swing hard on medical-cost trends.

What to watch (public or private). Same-clinic revenue and visit growth; revenue and visits per full-time-equivalent clinician; appointment capacity, wait times, no-show rates; payer mix, reimbursement rates, collections, denials, and days in accounts receivable; clinician turnover and retention; rent/occupancy by site; organic growth versus revenue acquired through deals; and under risk contracts, attributed patients, PMPM revenue, medical-cost ratio, quality scores, and shared savings/losses. A practice can post strong reported revenue growth while producing weak cash flow if collections deteriorate, clinicians leave, or acquired locations fail to integrate.

6. What drives demand

• Demographics. The population age 65 and older reached 61.2 million in 2024 — 18.0% of all Americans [9], and older patients use far more physician care. Rising Medicare enrollment is the single biggest structural tailwind.
• Chronic disease. Growing prevalence of diabetes, heart disease, obesity, and multiple chronic conditions drives visit volume.
• Insurance coverage. More insured patients means more paid demand; coverage losses (e.g., Medicaid disenrollment) cut it and worsen payer mix.
• Medicare Advantage penetration. The shift of seniors into private MA plans is what feeds the capitation / value-based-care model.
• Policy models. The Centers for Medicare & Medicaid Services (CMS) launched the ACO Primary Care Flex model in 2025 (running through 2029) to test prospective, up-front primary-care payments inside accountable care organizations — a nudge toward value-based primary care [13].
• Physician supply. Demand routinely outruns doctor supply. The Bureau of Labor Statistics (BLS) projects physician-and-surgeon employment to grow about 3% from 2024 to 2034, ~23,600 openings a year (a labor projection, not a revenue forecast) [10]; shortages and burnout cap how much care can be delivered and push up labor costs.
• Site-of-care shift and convenience. Care keeps moving from hospitals to lower-cost outpatient, office, retail, and telehealth settings, expanding what offices do.

7. Regulation

Physician offices sit inside one of the most heavily regulated revenue models in the economy:

• Medicare payment (CMS). The annual Physician Fee Schedule and its conversion factor effectively set the industry's price floor. Critically, the schedule has no automatic inflation update and must stay budget-neutral, so raising the value of one service forces cuts elsewhere — producing several consecutive years of headline conversion-factor cuts [11].
• MACRA / Quality Payment Program. The Medicare Access and CHIP Reauthorization Act (MACRA) pushes doctors toward either the Merit-based Incentive Payment System (MIPS, pay-for-performance reporting) or Advanced Alternative Payment Models (APMs). Beginning in 2026, Medicare splits into two conversion factors — a higher one ($33.57) for qualifying APM participants and a lower one ($33.40) for everyone else — plus a one-year statutory +2.5% update, the first meaningful raise in years [12].
• Corporate Practice of Medicine (CPOM). Roughly two-thirds of states restrict non-physician corporations from owning practices or employing doctors for clinical work. This is the structural reason outside capital enters through an MSO that owns the business while a physician-owned professional corporation holds the clinical license (Section 2). A flawed MSO, fee-split, or compensation arrangement can impair a platform's value [14].
• Fraud-and-abuse law. The Stark Law (physician self-referral) restricts referrals for designated Medicare services when a prohibited financial relationship exists [15]; the Anti-Kickback Statute bars paying or receiving anything of value to induce federal-program referrals, with False Claims Act exposure layered on top [16]. Penalties are severe.
• Privacy and billing. The Health Insurance Portability and Accountability Act (HIPAA) governs patient-data protection for practices and their business associates [17]; the No Surprises Act limits out-of-network balance billing and requires good-faith estimates [18].
• Other. State licensure, credentialing, scope-of-practice rules, malpractice liability, payer prior-authorization, coding/documentation, quality reporting, and cybersecurity. Regulatory diligence is not a back-office exercise — a flawed MSO, referral contract, coding practice, or risk-adjustment process can impair a platform's value.

8. Competitive dynamics and consolidation

At the national level this is about as unconcentrated as an industry gets — CR4 receipts share 6.2%, CR50 23.2%, HHI 18.5 [2]. But that national picture hides intense local consolidation, because patients, physicians, referral relationships, and payer contracts are all geographically specific. Three overlapping waves of buyers drive it:

1. Hospitals and health systems — the biggest consolidator, now employing 34.5% of physicians [7], often adding facility fees after acquisition.
2. Health insurers — vertical integration, led by UnitedHealth/Optum (~90,000 physicians) [19], with CVS (Oak Street), Humana (CenterWell), and Amazon (One Medical) buying primary care to feed Medicare Advantage and consumer channels.
3. Private equity — specialty roll-ups (dermatology, GI, ophthalmology, anesthesia, orthopedics, urology) built through MSO structures, where the sponsor owns the management company and captures a management fee plus equity upside while doctors retain nominal clinical ownership [14].

Scale can genuinely improve billing/collections, recruiting, purchasing, technology, referral capture, data/care management, payer negotiating leverage, and the ability to accept downside risk. The limits are local physician relationships, clinical culture, payer variation, state ownership laws, and integration difficulty.

The Federal Trade Commission's (FTC) 2025 physician-market research (a "6(b)" study) documented frequent serial acquisitions and heavy health-system involvement [21], and in early 2025 the agency settled an antitrust case against Welsh Carson over the U.S. Anesthesia Partners roll-up, imposing limits on involvement and notice/approval requirements for specified future hospital-based physician deals [22]. Federal attention has since cooled, but states are stepping up — several have enacted merger-notification and PE/MSO oversight laws [14]. The net effect: independent practice is shrinking, local markets are concentrating in specific specialties, and clinical decisions increasingly answer to corporate owners.

9. Risks

• Reimbursement pressure. The annual Medicare fee fight, no built-in inflation update, and budget-neutrality cuts squeeze FFS margins [11]; commercial and Medicaid rate pressure and contract terminations compound it.
• The cost squeeze. Labor, rent, and supply costs have climbed faster than revenue; MGMA data show operating costs rising while revenue grows at only a minority of practices — margins are thinning [23].
• Value-based-care / MA downside. Capitation can blow up when medical costs run above premium (MLR spikes), risk adjustment misses, or quality penalties bite. agilon, P3, and others have taken sharp hits from cost-trend misses; MA rate and coding changes add policy risk. This is the single biggest earnings risk for the public enablers.
• Payer concentration. A few health plans can control local contracting economics.
• Revenue-cycle risk. Coding errors, denials, slow collections, and weak documentation turn billed volume into poor cash flow.
• Regulatory and antitrust scrutiny. CPOM enforcement is a live threat to MSO structures; Stark/AKS, fee-splitting, privacy, and state PE/MSO oversight all affect ownership and deal structures [14][22].
• Integration and leverage risk. Debt-funded roll-ups are vulnerable when physicians, staff, or referral sources fail to transfer, or when reimbursement weakens.
• Coverage policy. Federal Medicaid tightening reduces covered demand and worsens payer mix for exposed practices.
• Workforce. Shortages, burnout, and administrative burden limit capacity and raise costs.
• Clinical and malpractice risk. A quality failure can damage both cash flow and reputation.
• Technology disruption. Telehealth, AI-assisted diagnostics, and new care models could reshape volumes and economics either way.
• Data limitations. Public parents rarely disclose clean NAICS 621111 revenue, and federal employer statistics exclude the smallest and government-run practice universe (Section 3).

10. How to invest, and the outlook

Public-market routes — split the exposure into three buckets:

1. Physician enablement and risk — PRVA, AGL, ASTH, PIII. The closest thing to a direct physician-office bet, but really wagers on managing Medicare Advantage medical costs, not office throughput. Small-cap, high-volatility, and highly sensitive to MLR trends.
2. Diversified integrators / direct delivery — UNH (Optum), CVS (Oak Street), HUM (CenterWell), AMZN (One Medical). Employed physicians are a strategic piece of a much larger insurance/pharmacy/retail machine; exposure is diluted. Analyze the segment, not the parent — CVS has signaled fewer new Oak Street openings and some clinic closures for 2026 [25], and UnitedHealth has flagged Optum Health restructuring and expected losses in certain value-based businesses [24], proof that scale does not eliminate execution risk.
3. Strategic specialty platforms / adjacent plays — CAH (Specialty Alliance/GI Alliance/Solaris), SGRY (surgical facilities), plus ambulatory-surgery operators, physician-staffing firms, and revenue-cycle/health-IT vendors that sell into practices.

Private-market routes (where most of the real economics live):

• Direct practice ownership, buy-ins, or partnership tracks.
• Private-equity funds and MSO platforms rolling up specialties.
• Medical-office real estate — directly or via healthcare real estate investment trusts (REITs) such as Healthpeak or Healthcare Realty that own the buildings practices lease.

Diligence questions for a private buyer. Are collections and cash earnings backed by actual payer remittances? How dependent is the practice on its selling physicians, and will they stay after close? Are payer contracts transferable and economically attractive? Is growth organic/de novo or acquisition-driven? Are owner-physician salaries normalized to market? Is the MSO structure legally sound in every state it operates? What are the coding, malpractice, audit, and compliance histories? How much downside sits in capitation or shared-risk contracts? Is leverage appropriate for a labor-sensitive business?

Outlook. The base case is constructive but selective. The 2026 fee schedule's +2.5% statutory bump and new APM-linked conversion factor are the first real Medicare raise in years and modestly ease FFS pressure [12]. The dominant force remains consolidation — hospitals, insurers, and PE keep absorbing independent practices — set against a rising wall of state regulation of PE/MSO ownership [14]. For the public enablers, the swing factor is Medicare Advantage: favorable rates and disciplined medical-cost management would validate the capitation model, while another round of cost-trend misses would punish them. The structural tailwind — an aging population needing more care — is not in doubt; the open questions are who captures the margin and whether regulators let the current owners keep it. The supplied federal file contains no NAICS-specific revenue-growth forecast, margin benchmark, or complete ownership census, and none is asserted here [1][2].

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Sources

1. U.S. Census Bureau, County Business Patterns 2023 (NAICS 621111: establishments, employment, annual and Q1 payroll). https://www.census.gov/programs-surveys/cbp.html
2. U.S. Census Bureau, 2022 Economic Census — Concentration / Comparative Statistics (NAICS 621111: receipts, firms, CR4/CR8/CR20/CR50, HHI). https://data.census.gov/table/ECNSIZE2022.EC2200SIZECONCEN?q=EC2200SIZECONCEN
3. U.S. Census Bureau, North American Industry Classification System — 621111 Offices of Physicians (except Mental Health Specialists) (scope and cross-references), 2022. https://www.census.gov/naics/?details=621111&input=621111&year=2022
4. U.S. Census Bureau, Nonemployer Statistics (methodology; no 621111 nonemployer figure in the supplied file). https://www.census.gov/programs-surveys/nonemployer-statistics.html
5. U.S. Small Business Administration, Table of Small Business Size Standards (NAICS 621111: $16 million average annual receipts), 2023. https://www.sba.gov/document/support-table-size-standards
6. Centers for Medicare & Medicaid Services, National Health Expenditure Fact Sheet (2023 data; physician and clinical services $978B, ~20% of health spending). https://www.cms.gov/data-research/statistics-trends-and-reports/national-health-expenditure-data/nhe-fact-sheet
7. American Medical Association, Physician Practice Benchmark Survey — Physician Practice Arrangements in 2024 (ownership mix: 42.2% private practice, 34.5% hospital-owned, 6.5% private-equity). https://www.ama-assn.org/about/research/physician-practice-benchmark-survey
8. Association of American Medical Colleges (AAMC), U.S. Physician Workforce Data Dashboard / 2025 Key Findings (~1,032,365 active physicians; ~866,000 in direct patient care). https://www.aamc.org/data-reports/data/2025-key-findings
9. U.S. Census Bureau, Older Adults Outnumber Children in 11 States (65+ population 61.2 million, 18.0% in 2024), 2025. https://www.census.gov/newsroom/press-releases/2025/older-adults-outnumber-children.html
10. U.S. Bureau of Labor Statistics, Occupational Outlook Handbook: Physicians and Surgeons (3% projected growth 2024–2034; ~23,600 annual openings). https://www.bls.gov/ooh/healthcare/physicians-and-surgeons.htm
11. Centers for Medicare & Medicaid Services, Calendar Year 2025 Medicare Physician Fee Schedule Final Rule (conversion factor $32.35), 2024. https://www.cms.gov/newsroom/fact-sheets/calendar-year-cy-2025-medicare-physician-fee-schedule-final-rule
12. Centers for Medicare & Medicaid Services, Calendar Year 2026 Medicare Physician Fee Schedule Final Rule (CMS-1832-F) (dual conversion factors $33.57 / $33.40; +2.5% statutory update), 2025. https://www.cms.gov/newsroom/fact-sheets/calendar-year-cy-2026-medicare-physician-fee-schedule-final-rule-cms-1832-f
13. Centers for Medicare & Medicaid Services, ACO Primary Care Flex Model (2025 launch; runs through 2029). https://www.cms.gov/priorities/innovation/innovation-models/aco-primary-care-flex-model
14. American Medical Association, Corporate Practice of Medicine overview, and Milbank Memorial Fund, How MSOs Are Reshaping Physician Practices (CPOM doctrine, MSO structures, state PE/MSO oversight trends). https://www.ama-assn.org/practice-management/private-practices/corporate-practice-medicine; https://www.milbank.org/publications/the-corporate-backdoor-to-medicine-how-msos-are-reshaping-physician-practices/
15. Centers for Medicare & Medicaid Services, Physician Self-Referral (Stark Law). https://www.cms.gov/medicare/regulations-guidance/physician-self-referral
16. U.S. Department of Health and Human Services, Office of Inspector General, Fraud & Abuse Laws (Anti-Kickback Statute, False Claims Act). https://oig.hhs.gov/compliance/physician-education/fraud-abuse-laws/
17. U.S. Department of Health and Human Services, HIPAA for Professionals — Covered Entities and Business Associates. https://www.hhs.gov/hipaa/for-professionals/covered-entities/index.html
18. Centers for Medicare & Medicaid Services, No Surprises Act — Provider Requirements and Resources. https://www.cms.gov/nosurprises/policies-and-resources/provider-requirements-and-resources
19. STAT News, UnitedHealth/Optum is the largest employer of physicians (~90,000 doctors, ~10% of U.S. workforce), 2023. https://www.statnews.com/2023/11/29/unitedhealth-doctors-workforce/
20. The Permanente Medical Groups / Kaiser Permanente, Our Medical Groups (>25,000 physicians; largest U.S. medical group). https://permanente.org/our-medical-groups/
21. U.S. Federal Trade Commission, First Research Published from Physician 6(b) Study, 2025. https://www.ftc.gov/enforcement/competition-matters/2025/06/first-research-published-physician-6b-study
22. U.S. Federal Trade Commission, FTC Secures Settlement with Private Equity Firm in Antitrust Roll-Up Scheme Case (Welsh Carson / U.S. Anesthesia Partners), 2025. https://www.ftc.gov/news-events/news/press-releases/2025/01/ftc-secures-settlement-private-equity-firm-antitrust-roll-scheme-case
23. Medical Group Management Association (MGMA), Provider Compensation and Cost & Revenue data reports (physician-owned vs. hospital-owned collections; operating-cost trends), 2025–2026. https://www.mgma.com/data
24. UnitedHealth Group, 2025 Form 10-K (Optum Health physician exposure; restructuring and value-based-care disclosures), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/731766/000073176626000062/unh-20251231.htm
25. CVS Health, 2025 Form 10-K (Oak Street Health / Health Care Delivery; 2026 openings and closures), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/64803/000006480326000010/cvs-20251231.htm
26. Humana, 2025 Form 10-K (CenterWell / Conviva senior primary care), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/49071/000004907126000009/hum-20251231.htm
27. Amazon.com, 2025 Form 10-K (One Medical), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1018724/000101872426000004/amzn-20251231.htm
28. Privia Health Group, 2025 Form 10-K (physician-enablement/MSO model; value-based lives), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1759655/000175965526000010/prva-20251231.htm
29. Astrana Health, 2025 Form 10-K (affiliated medical groups, MSOs, ACOs, risk-bearing care), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1083446/000119312526103128/asth-20251231.htm
30. agilon health, 2025 Form 10-K (Medicare Advantage full-risk enablement; membership), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1831097/000162828026011655/agl-20251231.htm
31. Cardinal Health, Second Quarter Fiscal 2026 Form 10-Q (The Specialty Alliance / GI Alliance / Solaris Health), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/721371/000072137126000006/cah-20251231.htm
32. Surgery Partners, 2025 Form 10-K (surgical facilities and physician practices), via SEC EDGAR. https://www.sec.gov/Archives/edgar/data/1638833/000163883326000008/sgry-20251231.htm
33. P3 Health Partners, Form 10-K annual report (senior-focused value-based primary care), via SEC EDGAR. https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=PIII&type=10-K
34. Corporate disclosures of private operators — ChenMed, TeamHealth (Blackstone portfolio), U.S. Anesthesia Partners, U.S. Dermatology Partners. https://www.chenmed.com/about-us; https://www.blackstone.com/news/; https://www.usap.com/about; https://www.usdermatologypartners.com/about-us/
35. Financial-data aggregators (market capitalizations and membership figures for PRVA, AGL, ASTH, PIII), mid-2026. https://stockanalysis.com/stocks/prva/