Medi-Cal Provider Participation by County
Click a county or search below to explore access data.
| County | Rate ▲ | Active | Registered | Phantom Gap |
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Participation by Specialty
Registered vs. Active Providers by Specialty
Monthly Participation Index (Jan 2019 = 100)
Why Does Participation Vary?
Medi-Cal pays the same flat rate statewide, but practice operating costs differ sharply by county. The index below measures local costs relative to the state average (100). Counties above 100 face higher costs on the same payment.
Composite index weights follow Medicare's Practice Expense GPCI: 56% employee wages, 30% facility rent, 14% purchased services.
Participation Rate vs. Practice Operating Costs (All CA Counties)
About the Access Explorer
The economic problem
Medicare adjusts physician payments by geography through the Geographic Practice Cost Index (GPCI), recognizing that it costs more to run a practice in San Francisco than in Modoc County. Medi-Cal does not. It pays flat statewide rates regardless of local wages, rents, or supply costs. The predictable result: the same Medi-Cal payment buys less provider time in high-cost counties, and providers in those counties are more likely to opt out entirely.
This tool quantifies that pattern. For each county, it compares the total pool of licensed providers (from NPPES) against those actively billing Medicaid (from the HHS Medicaid Provider Spending dataset released February 2026), and overlays a composite practice cost index (GPCI-aligned weights: 56% healthcare employee wages, 30% facility rent, 14% purchased services) to show how flat-rate reimbursement translates into different effective payment levels across the state.
What this measures (and what it doesn't)
The participation rate here shows what share of all licensed providers in a county choose to bill Medicaid. That measure differs from phantom network measurement, where the denominator is providers listed in a managed care plan's directory. Zhu et al. (2023, Health Affairs) measured phantom networks using actual plan directories and found 58.2% of listed providers in Oregon Medicaid were phantom. The HHS Office of Inspector General (OEI-02-23-00540, 2025) found that more than one-third of Medicaid-listed physicians nationally were phantom listings.
Our measure is broader: a provider in NPPES who does not bill Medicaid may never have opted into the program. But participation rates still reveal how economically attractive Medicaid reimbursement is in each local market, and the geographic pattern, driven by the mismatch between flat rates and variable costs, is the same one that produces phantom networks downstream. CMS finalized network adequacy rules effective July 2025 (CMS-2439-F) requiring states to verify directories against actual utilization.
Frequently Asked Questions
Why is this an economics problem?
Medi-Cal reimbursement is set statewide with no geographic adjustment for local operating costs. Medicare recognized this problem decades ago and adjusts payments through the GPCI. Without a similar adjustment, Medi-Cal's flat rates create an implicit penalty for practicing in high-cost areas: a provider in San Francisco faces operating costs roughly 30% above the state average but receives the same payment as a provider in a low-cost rural county. Provider participation rates reflect this mismatch.
Is this the same as a phantom network?
Not exactly. A phantom network refers to providers listed in a managed care plan's directory who do not actually see patients. This tool measures something broader: the share of all licensed providers (from NPPES) who actively bill Medicaid. A provider who does not bill Medicaid may never have claimed to accept it. But low participation rates and phantom networks share the same economic root cause: reimbursement that does not cover local practice costs. The geographic pattern this tool reveals is a leading indicator of where phantom networks are likely to form.
What data sources does the Access Explorer use?
The tool cross-references two federal datasets: the National Plan and Provider Enumeration System (NPPES) for all licensed providers, and the HHS Medicaid Provider Spending dataset (released February 2026) for providers actively billing Medicaid. NPPES captures the full licensed provider pool, not Medicaid-specific directories, so the participation rate shows what share of available providers choose to participate.
Which specialties are covered?
The tool covers six specialty categories: Primary Care, Behavioral Health, Dental, OB/GYN, Other Surgical, and Pharmacy & DME. Behavioral health typically shows the lowest Medicaid participation rates statewide, consistent with the findings of Zhu et al. (2023).
How often is the data updated?
Data is updated quarterly as new HHS Medicaid spending data becomes available. The current dataset covers January 2018 through December 2024. NPPES data is refreshed monthly.
Related resources
- Full methodology documentation (data processing, taxonomy crosswalks, cost index construction)
- Public Health ROI Calculator (estimates mortality reduction from county public health spending)
- Methods Lab (interactive tutorials on causal inference, cost-effectiveness, and program evaluation)
Last updated: February 2026