Freestanding Ambulatory Surgical and Emergency Centers (U.S., NAICS 621493)

1. Overview

When you have a colonoscopy, a cataract removed, a knee scoped, or a broken wrist set — and you go home the same day, to a building that is not a hospital — you have used this industry. NAICS code 621493 covers freestanding ambulatory surgical centers (ASCs) — outpatient operating suites that run scheduled procedures without an overnight stay — together with freestanding emergency, trauma, and urgent-care centers that operate independently of a hospital [1].

Why this matters, and to whom: the industry sits on one of the clearest structural shifts in U.S. health care — the migration of surgery out of expensive inpatient hospital beds into lower-cost outpatient settings. Medicare and commercial insurers keep steering procedures toward ASCs because they cost far less for the same operation, and the federal government keeps widening the list of procedures it will pay for in an ASC [7]. That tailwind is real, but it does not fall evenly. Returns in this business are local: payer contracts, physician alignment, case volume, labor costs, and state regulation drive results more than national procedure growth alone.

For public-market investors, direct exposure is scarce and usually indirect — the listed names are diversified hospital companies, insurers, or a single pure-play (Section 4). The larger truth is that the industry is overwhelmingly private and physician-owned: most ASCs have some doctor ownership, and private capital — private equity, insurer-owned platforms, hospital joint ventures, and the real estate under the centers — is where most of the money and the consolidation activity sit.

2. What it is and how it is structured

The North American Industry Classification System (NAICS) definition covers two related but economically different businesses under one code: scheduled outpatient surgery and freestanding emergency or urgent care [1].

In scope:

• Ambulatory surgical centers (ASCs) — freestanding operating and recovery suites for scheduled procedures such as colonoscopy, cataract surgery, arthroscopy, and pain injections. This is the bulk of the industry's revenue. Common specialties are gastroenterology (colonoscopy/endoscopy), ophthalmology (cataracts), orthopedics, and pain management [5][31].
• Freestanding emergency departments (FSEDs) and trauma centers — unscheduled walk-in emergency care not attached to a hospital, concentrated heavily in Texas and a few other states.
• Freestanding, licensed urgent-care centers (other than those run by hospitals or physician offices) [1].

Excluded — and where those adjacent activities are classified:

• Hospitals that also run operating rooms and emergency departments — NAICS subsector 622 (Hospitals). This is the single most important boundary: a hospital's own outpatient surgery department is not in 621493 [1].
• Physicians' offices / walk-in centers with procedure rooms — NAICS 621111 (Offices of Physicians).
• Kidney dialysis centers — NAICS 621492.
• HMO (health maintenance organization) medical centers — NAICS 621491.
• All other outpatient care centers (e.g., outpatient mental-health, non-dialysis specialty clinics) — NAICS 621498 [1].

Ownership. A typical ASC is a separate facility entity owned by some mix of physicians, a health system, and an operating company. A management services organization (MSO) often provides staffing, scheduling, billing, purchasing, IT, compliance, and payer contracting; the operator earns management fees and a share of facility profit, while physician owners receive distributions tied to their equity [14]. Ownership is mostly for-profit and physician-linked: MedPAC (the Medicare Payment Advisory Commission, an independent agency that advises Congress) reports that 95.3% of Medicare-certified ASCs were for-profit in 2024, and most had partial or complete physician ownership; the remainder are held by hospitals, corporate operators, payers, and private-equity firms [5]. Most ASCs are single-specialty [5].

3. How big it is

These are the ground-truth federal figures for NAICS 621493. They come from different federal programs and reference years, so they should not be read as one synchronized market-size estimate.

The Small Business Administration (SBA) threshold is a federal contracting classification, not an estimate of typical company size or industry revenue [4].

Concentration — highly fragmented. The four largest firms take just 17.5% of receipts, the top eight 23.2%, the top twenty 30.7%, and the top fifty 39.3% [2]. The Herfindahl-Hirschman Index (HHI) — a standard concentration gauge where anything under 1,500 is considered unconcentrated — is only 116 [2]. Even the biggest national chains own a small slice of a market made up of thousands of independent, doctor-owned centers.

Undercount caveats — two matter here. First, the code blends three businesses — surgery centers, freestanding ERs, and urgent care — so the $44.08 billion receipts figure is not "ASCs alone." Third-party researchers who count only ambulatory surgery centers put that sub-market near $45–46 billion for 2024 [12], implying ASCs account for most of the code's revenue. Second, the federal business statistics count establishments and firms with paid employees; County Business Patterns (CBP) excludes nonemployers, the self-employed, and businesses without an employer identification number, and can miss small multiunit sites [3]. Industry trackers instead count licensed facilities and reach a higher number — roughly 12,300 ASCs in mid-2025 (about 6,500 Medicare-certified and 5,800 not) [11]; MedPAC separately counted 6,436 Medicare-certified ASCs in 2024 [5]. The gap reflects very small or newly opened centers, procedure suites counted under physicians' offices, and hospital-affiliated ASCs that land in NAICS 622. The federal file provides no national count of procedures, operating rooms, utilization, payer mix, or profit margins — none of those should be inferred from the figures above.

4. The investable universe

There are only a few public ways to own this industry directly, and for most of them ambulatory surgery is one piece of a larger company. Facility counts below are not directly comparable with NAICS 621493, because public companies combine ASCs with surgical hospitals, endoscopy centers, physician practices, urgent care, and emergency departments.

Public companies

None of these is a pure NAICS 621493 exposure. The relevant question for a public investor is how much earnings come from same-facility outpatient operations rather than hospitals, acquisitions, or unrelated healthcare businesses.

Major private owners and platforms

The three largest operators are USPI (Tenet, public), SCA Health (Optum/UnitedHealth), and AMSURG; by one industry tally the top three hold roughly 17% of the market [13].

• AMSURG — private operator with more than 245 ASCs in 34 states and D.C. Ascension agreed to acquire it for $3.9 billion, but the Federal Trade Commission (FTC) required divestitures and the matter was still listed as pending in 2026 [22][23].
• SurgCenter Development, Regent Surgical, Compass Surgical Partners, Constitution Surgery Alliance and a long tail of private-equity-backed specialty roll-ups (GI, orthopedics, ophthalmology). Regent has backing from TowerBrook Capital Partners and an alignment with Ascension; Constitution took a growth investment from Welsh, Carson, Anderson & Stowe; Compass is associated with Health Velocity Capital and TPG (~40 ASCs) [24][25].
• The most active insurer buyer is Optum, which entered by paying ~$2.3 billion for SCA in 2017 and has since absorbed PE-backed platforms including PE GI Solutions, OrthoAlliance (2024), and U.S. Digestive Health (2025) [28].

Freestanding ERs and urgent care are almost entirely private. The remaining market is physician-owned centers, hospital joint ventures, specialty platforms, and small regional management companies.

5. How the money works

An ASC earns a facility fee — the "technical" charge for the room, staff, equipment, and supplies — billed separately from the surgeon's and anesthesiologist's professional fees. Medicare pays ASCs under a dedicated fee schedule for covered procedures [6][7]. Revenue reduces to a simple identity: cases × net revenue per case, driven by two levers:

• Case volume — how many procedures, set by the number and productivity of the physicians who use the center and by operating-room utilization; and
• Revenue per case — set by payer mix and case acuity.

Payer mix and acuity are the profit engine. Commercial insurers pay multiples of what Medicare and Medicaid pay, so a center weighted toward commercially insured patients earns far more per case; and higher-acuity work — orthopedics, spine, cardiology — carries much larger fees than a routine colonoscopy. Surgery Partners' 2024 results show the mechanism: same-facility revenue rose 8.0%, split into 3.9% more cases and 4.0% higher revenue per case [16]. That decomposition of "same-facility" (same-store) growth into volume and price is the number public investors watch most.

The site-of-service differential is the whole value proposition. Medicare pays an ASC substantially less than a hospital outpatient department (HOPD) for the identical procedure — MedPAC puts the average difference for shared services at about 46% [5], and HFMA illustrates it with a diagnostic colonoscopy at roughly $370 in an ASC versus $710 in an HOPD [10]. That gap is why insurers and employers steer patients to ASCs — and, paradoxically, why hospitals buy physician practices and convert them to hospital-based departments to capture the higher HOPD rate [10].

The syndication model aligns doctors with the asset. Physicians buy equity in the center and receive distributions pro rata to ownership — legally, distributions cannot be tied to how many patients a doctor refers [27]. Because the surgeons are owners, they have a direct incentive to run cases there and keep the rooms full. The cost base is partly fixed (rent, equipment, compliance, core nursing, insurance, administration) and partly variable (implants, drugs, supplies, contract labor, anesthesia, billing). High utilization against the fixed base produces strong facility-level margins and real operating leverage; a weak referral base leaves expensive rooms idle. Growth is relatively capital-light: build a de novo center, buy an existing one, or recruit more physician-owners into an underused facility.

Useful investor metrics: same-facility cases and revenue, revenue per case, cases per operating room, cancellations, labor and supply/implant cost per case, payer mix, physician retention, complication and transfer rates, and cash conversion. Public investors should separate organic performance from acquisitions and new-center ramp-up, and note the split between consolidated facilities and minority-owned (equity-method) ventures.

6. What drives demand

• The structural shift to outpatient. Better minimally invasive techniques, improved anesthesia, and faster recovery keep moving surgery out of the hospital; a large majority of U.S. surgeries are now performed on an outpatient basis, and the frontier keeps advancing into more complex cases [5].
• Growing supply and volume. MedPAC reported 6,436 Medicare-certified ASCs in 2024, up 2.2% year over year (248 opened, 108 closed or merged); knee, hip, and shoulder replacements in ASCs grew materially [5].
• Regulator-expanded scope. Medicare's annual rule-making keeps adding procedures to the ASC Covered Procedures List. For 2026, CMS added 289 procedures under revised criteria and removed 271 codes from the "inpatient-only" list — including higher-value orthopedic, spine, and cardiac cases — beginning a multi-year phase-out of that list [7]. Each addition unlocks a higher-value case that can leave the hospital.
• Demographics. The U.S. population aged 65 and older reached 61.2 million (18.0%) in 2024 [32], driving the core ASC procedures — cataracts, colonoscopies, joint work [5][31].
• Payer and consumer economics. Because ASCs are cheaper for shared services, insurers and self-funded employers actively route patients to them, and patients often face lower cost-sharing [5].
• Emergency access. Freestanding ER and urgent-care demand tracks local population growth and convenience, but its volume and payer economics are less predictable than scheduled surgery.

7. Regulation

Regulation directly shapes the economics here.

• Medicare Conditions for Coverage (CfCs), licensure, and accreditation. CMS (the Centers for Medicare & Medicaid Services) defines a Medicare ASC as a distinct entity operating exclusively to provide surgical services, with patient stays not expected to exceed 24 hours; certified ASCs must meet federal CfCs (governance, patient rights, infection control, records, discharge) plus state licensure and accreditation (through bodies such as AAAHC or The Joint Commission) [6].
• Quality reporting. The ASC Quality Reporting (ASCQR) program publicly reports facility-level measures; missing its requirements cuts the annual Medicare ASC payment update by 2 percentage points [8].
• CMS payment rules — the biggest external swing factor. The annual OPPS/ASC final rule sets both the rate update and which procedures are payable. For 2026, CMS finalized a 2.6% ASC payment update (up from 2.4% proposed) alongside the covered-procedure additions above [7].
• Certificate of Need (CON). About three dozen states maintain CON laws requiring a state permit proving "need" before some new health facilities open [33]; MedPAC counted 22 states plus D.C. with CON requirements applying specifically to ASCs in 2024, with several states narrowing them [5]. Loosening CON is a recurring tailwind for new ASC development.
• Fraud-and-abuse law. The federal Stark Law (physician self-referral) generally does not bar a physician from owning and referring to an ASC — but the criminal Anti-Kickback Statute (AKS) does apply. Physician-owned ASCs rely on a dedicated safe harbor (42 C.F.R. § 1001.952(r)) that protects the ownership structure so long as distributions track equity, not referral volume [27].
• EMTALA. The Emergency Medical Treatment and Labor Act generally applies to hospitals and their dedicated emergency departments, not ordinary freestanding ASCs; a facility's obligation depends on its legal relationship to a hospital and how it is licensed and held out to the public [9].
• The No Surprises Act (2022). For the emergency side, this federal law banned "balance billing" for out-of-network emergency care at independent freestanding ERs [29], removing the out-of-network pricing arbitrage that had powered the FSED boom of the mid-2010s.

8. Competitive dynamics and consolidation

The structure is a long fragmented tail plus a consolidating head. Nationally the four largest firms held just 17.5% of receipts in 2022 and the top fifty 39.3%, with an HHI of 116 [2] — but competition is intense locally, where a few hospitals, physician groups, and operators may control referrals or payer access.

Scale helps with purchasing, revenue-cycle management, IT, quality reporting, recruiting, payer negotiation, and new-center development. Physician alignment stays critical because doctors control case flow. MedPAC's five largest corporate holders — USPI, AMSURG, HCA, Surgery Partners, and SCA Health — reached 21.5% of Medicare-certified ASCs in 2024 [5], leaving a long runway.

Three forces drive deal-making. First, hospitals partner with or acquire ASCs to defend outpatient volume and, where possible, convert facilities to higher-paid hospital departments [10]. Second, insurers — led by UnitedHealth's Optum — buy surgery centers and the physician groups that feed them, building payer-owned care delivery [28]. Third, private equity builds specialty roll-ups (GI, orthopedics, ophthalmology) and often flips them to strategic buyers — a "mom-and-pop to Walmart" evolution described across the sector [25][26].

Consolidation draws scrutiny. Research on Optum's ASC purchases found prices rose about 11% per procedure (~$239) within two quarters of acquisition, without a matching shift in referral patterns [28] — the kind of finding that invites antitrust attention. The FTC's review of the proposed Ascension–AMSURG deal, which required divestitures, shows that local overlap and payer-provider integration can trigger remedies even when national concentration looks modest [22]. The likely path is continued consolidation that is mostly regional and specialty-specific rather than a single national roll-up.

9. Risks

• Reimbursement. Revenue depends on annual CMS rate decisions and on commercial contract negotiations; Medicaid pays poorly, and a bad rule cycle or hard payer squeeze compresses margins. Prior authorization, denials, and site-of-care policies all bite.
• Site-neutral payment reform. Congress and MedPAC continue to weigh equalizing HOPD and ASC/office rates. It cuts both ways: neutral rates would erase hospitals' pricing advantage and could accelerate the shift to ASCs, but broad outpatient payment cuts would pressure everyone.
• Labor. Nurses, surgical techs, anesthesia providers, and physicians are hard to replace; wage inflation can offset volume growth — the largest controllable cost.
• Utilization and physician dependence. Elective cases can be delayed by economic weakness or high deductibles, and a center's economics can collapse if key owner-physicians retire, move, or change affiliation. Managing aging owner-doctors and buy-sell provisions is an ongoing risk.
• Regulatory/legal. AKS enforcement, changes to the physician-ownership safe harbor, quality-reporting penalties, and CON swings can reshape economics quickly.
• Emergency/urgent-care exposure. The FSED model was hit hard by the No Surprises Act and by overbuilding in Texas; its high-water-mark cautionary tale is Adeptus Health, whose First Choice ER network went from a 2014 IPO to bankruptcy in 2017 [30].
• Consolidation and antitrust. Acquisitions can bring integration strain, heavy leverage, and — given insurer/PE ownership and evidence of post-deal price increases — real antitrust and reputational exposure [22][28].
• Data risk. Federal business statistics exclude important categories of operators and are not a complete facility or procedure census (Section 3).

10. How to invest and the outlook

Public routes. The cleanest listed exposure is Surgery Partners (SGRY), the largest pure-play, and Tenet Healthcare (THC), whose USPI unit is the biggest ASC platform and the company's main growth driver [14][15][16]. HCA (HCA), UnitedHealth (UNH), and Universal Health Services (UHS) give diluted exposure inside much larger businesses [18][19][20]; Medical Facilities Corp. (DR) is a small, higher-risk pure surgical-hospital play [21]. Before comparing valuation multiples, isolate ASC earnings from hospitals, physician practices, urgent care, and other segments, and read the footnotes for same-facility cases, revenue per case, payer mix, ownership percentages, equity-method earnings, and acquisition spend. Private-equity interest reaches into the public names, too — Bain Capital's rejected 2025 bid for Surgery Partners shows how tightly public and private valuations are linked here [17].

Private routes. This is where most of the industry actually is. Accredited investors and institutions participate through PE funds building specialty ASC platforms, direct physician-ownership stakes (for practicing clinicians), and real-estate vehicles that own the buildings ASCs lease. The buyers with the most firepower — Optum, AMSURG, SurgCenter, Regent, and PE roll-ups — are all private. Underwrite the individual center, not the national trend: verify licenses, CON status, accreditation, and payer contracts; normalize historical cases, utilization, cancellations, and physician ownership; stress labor, supplies, anesthesia, rent, and malpractice; review transfer protocols, quality data, physician retention, and buy-sell terms; and model distributions, debt service, and the likely exit buyer.

Near-term drivers to watch: the annual CMS ASC payment rule and the pace of the inpatient-only-list phase-out (each new procedure added is incremental high-value volume) [7]; commercial payer contracting and steerage; the trajectory of site-neutral legislation; and the consolidation pace, including any antitrust response to insurer and PE ownership [22][28]. The multi-decade migration of surgery to lower-cost outpatient settings is still underway, regulators keep widening the door, and the market remains fragmented enough to consolidate for years. Surgical centers and emergency centers should be evaluated separately — their demand, staffing, reimbursement, and regulatory exposure are not interchangeable. The principal uncertainties are political — how Washington sets rates and whether it curbs the insurer-and-PE buying spree — rather than whether demand for lower-cost outpatient surgery will keep growing.

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Sources

1. U.S. Census Bureau. 2022 NAICS Definition — 621493 Freestanding Ambulatory Surgical and Emergency Centers (definition and exclusions). https://www.census.gov/naics/?details=62&input=62&year=2022
2. U.S. Census Bureau. 2022 Economic Census — Concentration of Largest Firms (firms, receipts, CR4/8/20/50, HHI), NAICS 621493. https://data.census.gov/table/ECNSIZE2022.EC2200SIZECONCEN
3. U.S. Census Bureau. County Business Patterns 2023 (establishments, employment, payroll), NAICS 621493. https://www.census.gov/data/datasets/2023/econ/cbp/2023-cbp.html
4. U.S. Small Business Administration. Table of Small Business Size Standards, 2023 (NAICS 621493, $19M). https://www.sba.gov/document/support-table-size-standards
5. Medicare Payment Advisory Commission (MedPAC). Report to the Congress, Ch. 11 — Ambulatory Surgical Center Services: Status Report, March 2026 (certified-ASC count/growth, for-profit and ownership mix, ~46% payment difference, CON count, top-5 corporate share). https://www.medpac.gov/wp-content/uploads/2026/03/Mar26_Ch11_MedPAC_Report_To_Congress_SEC.pdf
6. Centers for Medicare & Medicaid Services (CMS). Ambulatory Surgical Centers (certification, Conditions for Coverage). https://www.cms.gov/medicare/health-safety-standards/certification-compliance/ambulatory-surgery-centers
7. CMS. Calendar Year 2026 Hospital Outpatient PPS and Ambulatory Surgical Center Final Rule (2.6% ASC update; 289 procedures added; 271 codes off inpatient-only list). https://www.cms.gov/newsroom/fact-sheets/calendar-year-2026-hospital-outpatient-prospective-payment-system-opps-ambulatory-surgical-center
8. CMS. Ambulatory Surgical Center Quality Reporting (ASCQR) Program. https://www.cms.gov/medicare/quality/initiatives/asc-quality-reporting
9. CMS. Emergency Medical Treatment and Labor Act (EMTALA) — Interim Guidance. https://www.cms.gov/regulations-and-guidance/legislation/emtala/downloads/sc0410.pdf
10. Healthcare Financial Management Association (HFMA). HOPDs vs. ASC: Understanding Payment Differences, 2023 (colonoscopy ~$370 ASC vs ~$710 HOPD). https://www.hfma.org/operations-management/ambulatory-care/hopds-vs-asc-understanding-payment-differences/
11. ASC Data. ASC Industry Overview, August 2025 (~12,294 ASCs; Medicare-certified/non-certified split). https://ascdata.com/wp-content/uploads/2025/08/ASC-Data-Industry-Overview-August-2025.pdf
12. Fortune Business Insights. U.S. Ambulatory Surgical Centers Market, 2024–2025 (~$45.6B). https://www.fortunebusinessinsights.com/u-s-ambulatory-surgical-centers-market-106323
13. Becker's ASC Review. Top ASC operators by market share, 2025 (USPI, SCA, AMSURG counts and shares). https://www.beckersasc.com/asc-transactions-and-valuation-issues/top-5-asc-operators-by-market-share-2025/
14. U.S. SEC. Tenet Healthcare Corporation Form 10-K, FY2025 (USPI: 533 ASCs, 26 surgical hospitals). https://www.sec.gov/Archives/edgar/data/70318/000007031826000012/thc-20251231.htm
15. U.S. SEC. Surgery Partners, Inc. Form 10-K, FY2025 (157 ASCs, 19 surgical hospitals, 30 states). https://www.sec.gov/Archives/edgar/data/1638833/000163883326000008/sgry-20251231.htm
16. Surgery Partners, Inc. Fourth Quarter and Full Year 2024 Results (~$3.1B revenue; ~$508M adj. EBITDA; same-facility growth). https://ir.surgerypartners.com/news-releases/news-release-details/surgery-partners-inc-announces-fourth-quarter-and-full-year-2024
17. Surgery Partners, Inc. Bain Capital take-private proposal ($25.75/share; ~39% ownership) concluded, June 2025. https://ir.surgerypartners.com/news-releases/news-release-details/surgery-partners-inc-and-bain-capital-conclude-discussions
18. U.S. SEC. HCA Healthcare, Inc. Form 10-K, FY2025 (121 freestanding ASCs, 31 endoscopy centers). https://www.sec.gov/Archives/edgar/data/860730/000119312526044769/hca-20251231.htm
19. SCA Health (UnitedHealth/Optum). About Us (370+ clinical locations, 400 physician-practice clinics, 9,700 physicians). https://sca.health/about-us/
20. U.S. SEC. Universal Health Services, Inc. Form 10-K, FY2025 (35 freestanding EDs, 13 outpatient centers, 1 surgical hospital). https://www.sec.gov/Archives/edgar/data/352915/000119312526071676/uhs-20251231.htm
21. Medical Facilities Corporation. Fourth Quarter and FY2024 Results (TSX: DR; ~$331.5M facility revenue; AR/OK/SD surgical hospitals + CA ASC). https://www.newswire.ca/news-releases/medical-facilities-corporation-reports-fourth-quarter-and-fy-2024-results-854552350.html
22. Federal Trade Commission. Ascension/AMSURG, In the Matter of (divestitures; pending). https://www.ftc.gov/legal-library/browse/cases-proceedings/251-0093-ascensionamsurg-matter
23. Massachusetts Health Policy Commission. Notice of Material Change: Ascension and AMSURG ($3.9B; >245 ASCs). https://masshpc.gov/sites/default/files/2025-09/20250819%20Ascension%20MCN.pdf
24. Regent Surgical. How Private Equity Is Scaling ASCs Without Buying Surgery Centers (TowerBrook; Constitution Surgery Alliance/Welsh Carson). https://regentsh.com/how-private-equity-is-scaling-ascs-without-buying-surgery-centers/
25. Private Equity Stakeholder Project. Private Equity's Role in Ambulatory Surgical Centers, October 2025 (Compass Surgical Partners and other platforms). https://pestakeholder.org/wp-content/uploads/2025/10/PESP_Report_Ambulatory-Surgical-Centers_2025-compressed.pdf
26. Ambulatory Surgery Center News. From 'Mom and Pop' to Walmart: Regent, Compass, CHS Execs Explore the Fast-Changing ASC Landscape, 2026. https://ascnews.com/2026/07/from-mom-pop-to-walmart-regent-compass-chs-execs-explore-fast-changing-asc-landscape/
27. Little Health Law / National Law Review. ASC Physician Ownership: Stark vs. Anti-Kickback Statute and the ASC Safe Harbor (42 C.F.R. § 1001.952(r)), 2024. https://www.littlehealthlaw.com/blog/im-an-asc-owner-do-i-need-to-worry-about-the-stark-law/
28. Becker's ASC Review / Healthcare Brew. Optum–SCA consolidation ($2.3B, 2017); PE GI Solutions & OrthoAlliance (2024); U.S. Digestive Health (2025); post-acquisition price study (+11% / ~$239), 2024–2026. https://www.beckersasc.com/asc-transactions-and-valuation-issues/another-optum-power-play-shakes-up-the-asc-market/
29. CMS / U.S. Dept. of Labor. No Surprises Act — balance-billing protections at independent freestanding emergency departments, 2022. https://www.cms.gov/newsroom/fact-sheets/no-surprises-understand-your-rights-against-surprise-medical-bills
30. Adeptus Health (First Choice ER): 2014 IPO to 2017 bankruptcy. https://en.wikipedia.org/wiki/Adeptus_Health
31. Definitive Healthcare / HCUP. Most Common Procedures at ASCs (GI, ophthalmology, pain, orthopedics; cataract CPT 66984). https://www.definitivehc.com/resources/healthcare-insights/top-procedures-at-ascs
32. U.S. Census Bureau. Older Adults Outnumber Children in 11 States (61.2M aged 65+, 18.0%, 2024). https://www.census.gov/newsroom/press-releases/2025/older-adults-outnumber-children.html
33. FJ Law Group / state CON summaries. Certificate of Need programs (~three dozen states) and ASCs. https://fjlawgroup.com/news/does-the-stark-law-apply-to-ambulatory-surgery-centers/