Draft Almanac release · Independent analysis by CRWDHEALTH · Not endorsed by CHCF
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Market structure · 2024

Inpatient market shares by patient county

Choose a county to see which hospitals and health systems treated its residents in 2024. Every chart and table can be downloaded.

2024 · Inpatient + Inpatient from ED records · Agency for Healthcare Research and Quality (AHRQ) 2023 system linkage

System HHI2,388Herfindahl-Hirschman Index, 0 to 10,000
Top-four share86.5%Four largest systems or unclassified hospitals combined
Largest system34%Largest reported resident share
Resident discharges98,415138 reporting identities

2024 inpatient discharge destinations

Contra Costa County

Top ten systems or unclassified hospitals serving county residents. Shares use discharges at all reporting facilities as the denominator.

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Horizontal bars show the ten systems or unclassified hospitals receiving the largest shares of reported inpatient discharges for residents of Contra Costa County.1. Kaiser Permanente34%2. John Muir Health31%3. Sutter Health12.8%4. Contra Costa Health Services8.7%5. University of California Health4.4%6. Tenet Healthcare2.7%7. Stanford Health Care2%8. Alameda Health System0.5%9. Universal Health Services0.5%10. CommonSpirit Health0.5%0%34%

Method: Within each California residence county, combine the disjoint Inpatient (not from ED) and Inpatient from ED settings; exclude ED Only and AS Only. Aggregate by stable facility ID, not name. Shares divide each facility's inpatient discharges by all included discharges for that county. HHI is the sum of squared percentage shares (0–10,000). System HHI groups only explicit AHRQ 2023 system IDs reached through documented HCAI-to-CCN links; all others remain separately identified and unclassified.

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Data behind the visual

Exact system shares

Hospitals without an AHRQ system link are listed individually as unclassified. They are not grouped by name.

RankSystem or hospitalDischargesShareLinkage
1Kaiser Permanenteahrq:HSI0000053633,42834%AHRQ system
2John Muir Healthahrq:HSI0000053030,55331%AHRQ system
3Sutter Healthahrq:HSI0000105012,60112.8%AHRQ system
4Contra Costa Health Servicesahrq:HSI000002708,5158.7%AHRQ system
5University of California Healthahrq:HSI000011684,2834.4%AHRQ system
6Tenet Healthcareahrq:HSI000010662,6192.7%AHRQ system
7Stanford Health Careahrq:HSI000010331,9842%AHRQ system
8Alameda Health Systemahrq:HSI000000185190.5%AHRQ system
9Universal Health Servicesahrq:HSI000011485000.5%AHRQ system
10CommonSpirit Healthahrq:HSI000014274450.5%AHRQ system
Reading these shares

The patient-origin population is broader than the 299-hospital comparable financial cohort; discharge totals are not interchangeable. Residence counties are descriptive screens, not antitrust markets. No adjustment for service, payer or travel time is made. Non-California and unknown residences are excluded and tabulated. AHRQ 2023 affiliations predate 2024 flows. Unclassified does not mean independent; incomplete system linkage may understate concentration. This raw workbook contains numeric counts; suppression rules from other HCAI products are not assumed. Shares in small counties can swing widely, so read HHI together with discharge volume.

Documented ownership changes · checked September 26, 2026

Ownership-change sensitivity: 9 hospitals regrouped

9 hospitals in four documented 2024 closings (UCI Health–Tenet, UCLA Health–West Hills, UCSF Health–Dignity San Francisco, Rady Children’s–CHOC) are regrouped with their acquiring AHRQ system for all 2024 flows as a year-end ownership sensitivity. Baseline 2023 affiliations remain unchanged. This is not transaction-date-adjusted or a causal merger effect.

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HospitalMedicare CCNBaseline system (2023)Sensitivity systemEffective dateEvidence
UCI HEALTH-FOUNTAIN VALLEYHCAI 106301175050570Tenet HealthcareUniversity of California HealthSource ↗
UCI HEALTH-LAKEWOODHCAI 106190240050581Tenet HealthcareUniversity of California HealthSource ↗
UCI HEALTH-LOS ALAMITOSHCAI 106301248050551Tenet HealthcareUniversity of California HealthSource ↗
UCI HEALTH-PLACENTIA LINDAHCAI 106301297050589Tenet HealthcareUniversity of California HealthSource ↗
UCLA WEST VALLEY MEDICAL CENTERHCAI 106190859050481HCA HealthcareUniversity of California HealthSource ↗
ST. FRANCIS MEMORIAL HOSPITALHCAI 106380960050152CommonSpirit HealthUniversity of California HealthSource ↗
ST. MARY'S MEDICAL CENTER - SAN FRANCISCOHCAI 106380965050457CommonSpirit HealthUniversity of California HealthSource ↗
CHILDREN'S HOSPITAL OF ORANGE COUNTYHCAI 106300032053304CHOC ChildrensRady Childrens Hospital San DiegoSource ↗
CHILDREN'S HOSPITAL AT MISSIONHCAI 106304113053306CHOC ChildrensRady Childrens Hospital San DiegoSource ↗

System HHI changes in 47 of 58 counties

System HHI of resident inpatient discharges under 2023 affiliations and under year-end 2024 ownership. Counties with no change are in the download.

Residence countyResident dischargesBaseline system HHIYear-end ownership HHIChange
San Francisco71,7071,687.01,978.2+291.2
Orange272,5841,037.61,175.3+137.7
Calaveras4,8921,894.21,873.5-20.7
Los Angeles960,700552.7569.3+16.6
Ventura82,0601,348.21,334.1-14.1
Santa Cruz22,3112,731.72,721.6-10.1
Marin20,8092,965.02,974.6+9.6
Nevada9,4463,732.23,726.1-6.1
Siskiyou2,9493,066.03,059.9-6.1
Tehama6,6733,669.33,663.4-5.9
Shasta22,3614,128.04,122.3-5.7
Merced28,1222,389.82,384.3-5.5
Trinity1,2722,205.12,199.8-5.3
San Luis Obispo23,2262,744.22,739.5-4.7
San Mateo54,0001,929.01,925.4-3.6
Mendocino9,5084,555.64,559.1+3.5
Mono4892,258.62,262.0+3.4
San Joaquin74,9731,636.81,633.4-3.4
Humboldt12,3355,078.15,080.7+2.6
Sonoma44,0062,442.42,444.9+2.5
Sutter10,4724,034.64,036.8+2.2
Plumas1,0341,579.01,581.1+2.1
Solano37,9962,424.42,426.3+1.9
Alameda127,9851,821.81,823.6+1.8
Lassen1,2704,572.34,573.9+1.6
Contra Costa98,4152,387.62,389.1+1.5
Napa11,2243,131.23,132.6+1.4
Yuba9,4423,302.03,303.4+1.4
Lake8,3952,215.62,216.9+1.3
Inyo1,1674,347.94,349.0+1.1
Sacramento155,7782,356.82,355.7-1.1
Madera15,3132,589.12,588.1-1.0
Riverside241,265929.2928.2-1.0
Amador4,6004,295.44,294.6-0.8
El Dorado16,3481,727.81,727.1-0.7
Yolo16,8692,615.22,614.5-0.7
San Diego306,1121,594.21,594.8+0.6
Butte30,5913,684.73,685.1+0.4
Del Norte2,6326,447.06,447.4+0.4
Santa Barbara40,6953,557.63,557.2-0.4
Placer39,2623,691.83,691.5-0.3
Tuolumne6,0253,532.03,532.3+0.3
Monterey42,5592,503.12,503.3+0.2
San Bernardino223,334870.3870.1-0.2
Fresno105,4843,435.73,435.8+0.1
Santa Clara147,8091,514.41,514.3-0.1
Tulare43,5573,474.43,474.5+0.1

Limitation: Focused search of documented 2023–2024 closings; not a comprehensive ownership refresh. Patient-flow data lack transaction-date splitting. AHRQ groups the UC system broadly; transactions without an AHRQ destination and unclassified affiliations remain unresolved.

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