How is Medicare Advantage developing in San Bernardino County, California?
San Bernardino County's MA & other health plan share is 67.3% — above the 51.1% national share by 16.2 points, with 234,984 people in a Medicare Advantage or other health plan out of 349,071 Medicare beneficiaries, on the April 2026 CMS county file. It ranks 1 of 58 California counties by health plan share.
Why trust this number?
- Metric
- MA & other health plan share
- Value
- 67.3%
- Geography
- San Bernardino, CA (FIPS 06071)
- Period
- April 2026
- Source
- CMS Medicare Monthly Enrollment (BENE_GEO_LVL=County)
- Numerator
- MA_AND_OTH_BENES — beneficiaries in a Medicare Advantage or other health plan (includes cost plans, PACE and demonstrations) — 234,984 here
- Denominator
- TOT_BENES — all Medicare beneficiaries in the county with Part A and/or Part B — 349,071 here
- Formula
- 234,984 ÷ 349,071 × 100 = 67.3%
- Dataset vintage
- April 2026 (prior year April 2025)
- Last refreshed
- 2026-07-31
- Status
- LIVE
Full methodology · Download the source data · CMS dataset
The denominator counts everyone with Part A and/or Part B, including people with Part A only who cannot enroll in Medicare Advantage. Figures published elsewhere on an eligible-only denominator will read higher. Match the basis before comparing.
All figures on this row are from the April 2026 CMS Medicare Monthly Enrollment county file.
Market structure in San Bernardino County
| MA and other health plan enrollees | 234,984 |
| Total Medicare beneficiaries | 349,071 |
| MA & other health plan share | 67.3% |
| Dual eligibles | 99,738 (28.6% of Medicare) |
| Full-benefit dual eligibles | 99,067 |
| Market type | Mature (65%+ penetration) |
Every row is from the April 2026 CMS Medicare Monthly Enrollment county file. Carrier counts, the leading carrier and D-SNP share of MA are not shown because this site has no county-level carrier source yet — that needs the CMS CPSC ingest. They previously appeared here from a dataset that has since been withdrawn. Carrier-level enrollment and stars are tracked at the state level.
What changed in the last twelve months
April 2025 file compared with the April 2026 file. Source: CMS Medicare Monthly Enrollment (BENE_GEO_LVL=County).
| Measure | April 2026 | Change | Basis |
|---|---|---|---|
| MA & other health plan enrollment Computed by the pipeline from the two published monthly files. | 234,984 | +3.2% | observed |
| MA & other health plan share A ratio of two published counts, so the change carries both denominators. | 67.3% | +0.6 pp | derived |
| Medicare beneficiaries The county file publishes the current count. It does not publish a prior-year count for this county, and we do not reconstruct one. | 349,071 | not published as a change | observed |
| Dual eligibles Current count from the same file. Same limitation as the line above. | 99,738 (28.6% of Medicare) | not published as a change | observed |
These are observed changes. This panel does not assert why a figure moved: the county file records what happened, not what caused it. A release-over-release view, rather than this twelve-month view, needs the per-vintage metrics store described in docs/backend-architecture.md.
MedicareInsights Market Opportunity Score
| Market size | 100 pctile |
| Headroom | 8 pctile |
| Growth | 46 pctile |
| Enrollment growth | 63 pctile |
| Competition | not yet available |
| Carrier diversity | not yet available |
| Product opportunity | not yet available |
| Quality environment | not yet available |
How is this calculated?
Each component is converted to a percentile rank against all 3,199 US counties, then combined with published weights. Percentile ranking rather than min-max scaling, so one extreme county cannot compress the rest of the distribution.
Weights: market size 0.30, headroom 0.25, growth 0.25, enrollment growth 0.20. Because four of the eight planned components are not yet computable, the weights above are renormalized over the four that are, and the missing four are listed in the table rather than quietly dropped.
Not yet included: market concentration and carrier diversity (require the CMS contract/plan/county enrollment file), product opportunity (requires the Landscape and PBP benefit files), and quality environment (requires contract-level Star Ratings). Until those land, this score describes market attractiveness, not competitive difficulty.
Status: MODELED. It is a deterministic ranking of public CMS figures, not a prediction, not a recommendation, and not produced by a language model. The inputs are the same county file cited elsewhere on this page. Model version 0.1.
MODELED Market Opportunity Score v0.1 · computed from CMS Medicare Monthly Enrollment, county geography · methodology
So what / Now what Interpretation
San Bernardino County is a mature market at 67.3% penetration — expansion means winning members from incumbent MA plans on benefits, network and brand.
- Compare to the rest of California on the state page.
- Check 2026 plan exits for orphaned membership contestable in California.
- Sales teams: rank this market on health-plan share headroom and momentum in the county explorer, and see which competitive facts apply on the carrier battlecards.
Neighboring California counties
Provenance — MA & other health plan share, April 2026
- Source file
- CMS Medicare Monthly Enrollment (BENE_GEO_LVL=County)
- Vintage
- April 2026 (prior year April 2025)
- Ingested
- 2026-07-31
- Refresh cadence
- Monthly, following the CMS Medicare Monthly Enrollment release (CCW-derived, roughly three months in arrears)
- Method
- penetration_pct = MA_AND_OTH_BENES / TOT_BENES * 100, rounded to 1 decimal
- Coverage
- All 3199 US counties
- Known limitations
- The denominator includes beneficiaries with Part A only, who cannot enroll in Medicare Advantage. Figures that use an eligible-only denominator will be higher. This file does not carry carrier, plan or star-rating detail. Any such figure needs the CPSC ingest, which is not yet built.