NAICS 621111
Physician Practices in Diamond Bar, CA
The 1 ZIP codes assigned to Diamond Bar contained 50 Medical Practice establishments in 2023.
- Establishments (2023)
- 50
- 1 ZIP codes
- 10 or more employees
- n/a
- Practical financing floor
- Share of county
- 1%
- Los Angeles County
- City population
- 51,884
- 2025 estimate
Figures cover the ZIP codes the U.S. Postal Service assigns to Diamond Bar (91765). ZIP areas are not municipal boundaries: they can extend beyond city limits and are shared between neighbouring places. This is a count of establishments in Diamond Bar's ZIP codes, not a count of businesses inside its city limits.
Establishments by size
Employee-count distribution. For most buyers the businesses worth pursuing sit in the 5 to 49 range: large enough to have a manager and real systems, small enough to be owner-operated.
| Employees | Establishments | Share | Distribution |
|---|---|---|---|
| 1-4 | 42 | 84.0% | |
| 5-9 | 7 | 14.0% |
How this market compares
Diamond Bar against every other city in California on the same measure. City figures cover the ZIP codes assigned to the place rather than its municipal boundary, so they are compared as a share of the businesses in those same ZIP codes rather than per resident. Cities with fewer than 500 businesses in total are left unranked.
About the same slice of the local business base as the industry holds statewide.
- Vs state share
- -2%
- Share of local businesses
- Rank by count
- #122
- of 373 cities
- Rank by share
- #124
- of 297 ranked
- Since 2020
- -12%
- Change in establishments
This compares how much of Diamond Bar’s business base is physician practices, against the California figure. Base: 1,793 establishments across all industries in the same ZIP codes, 2023. It does not measure revenue, profitability or whether a market is worth entering.
Business size mix
Diamond Bar is more fragmented than California as a whole: a larger share of very small operators. Fragmented markets are where roll-ups are assembled, and where an owner nearing retirement has no obvious internal buyer.
| Share of establishments | Diamond Bar | California | Difference |
|---|---|---|---|
| Under 5 employeesOwner-operated, often no management layer | 84.0% | 65.6% | +18.4% |
| 5 to 49 employeesThe range most individual buyers target | 14.0% | 27.4% | -13.4% |
| 10 or more employeesPractical floor for acquisition financing | 0.0% | 12.9% | -12.9% |
Nearest comparable markets
The closest places to Diamond Bar that also have Medical Practice establishments on record. Useful for spotting a gap next door, or realising the market you are looking at is already served from the town over.
| Market | Establishments | Vs state share |
|---|---|---|
| Walnut | 35 | -47% |
| Pomona | 104 | +38% |
| Brea | 34 | -53% |
| West Covina | 92 | +38% |
| Chino Hills | 38 | -29% |
The wider Los Angeles County market
Employment and payroll are reported at county level only, so the figures below describe the county Diamond Bar sits in.
- County establishments (2023)
- 9,829
- Los Angeles County
- County employees
- 59,829
- Mid-March employment
- County annual payroll
- $6.4B
- All establishments
What acquirers look at
California’s corporate practice of medicine doctrine restricts lay ownership, so deals are structured as MSO arrangements. Not a first acquisition for an unlicensed buyer.
Other industries in Diamond Bar
Nearby cities
Sources
- U.S. Census Bureau, 2023 ZIP Code Business Patterns. Establishment counts and size distribution by ZIP code and NAICS, aggregated over the ZIP codes assigned to each city. Retrieved 2026-09-08.
- U.S. Census Bureau, 2023 County Business Patterns. Establishment counts, employment and annual payroll by NAICS. Retrieved 2026-09-08.
- U.S. Bureau of Labor Statistics, Quarterly Census of Employment and Wages (2026Q1). Quarterly establishment counts and employment for employers covered by unemployment insurance. Retrieved 2026-09-08.