Glossary

Jump to: MA penetration (and its bases) · Star ratings · Quality bonus payment · MOOP · MFP (maximum fair price) · D-SNP · C-SNP · I-SNP · FIDE-SNP · V28 (CMS-HCC model) · CPSC files · HHI · PMPM · Velocity · ANOC (Annual Notice of Change) · AEP (Annual Enrollment Period) · OEP (MA Open Enrollment Period) · SEP (Special Enrollment Period) · LIS (Low-Income Subsidy / Extra Help) · Disenrollment rate · Runway score · Crosswalk

MA penetration (and its bases)#

The share of Medicare beneficiaries enrolled in Medicare Advantage in a geography. The number depends on its basis: the CMS monthly-file basis counts MA + other health plan enrollment over all Medicare beneficiaries (Parts A and/or B); the plan-year pure-MA basis counts only MA plans; KFF's widely cited eligible-only basis divides by beneficiaries eligible to enroll and runs several points higher. Every page on this site states its basis next to the number — cite the basis with the figure.

Star ratings#

CMS's 1-to-5 quality score for each MA and Part D contract, published once a year in October for the following plan year. Ratings combine clinical (HEDIS), survey (CAHPS), and operations measures, each with a weight. CMS does not publish quarterly ratings — any sub-annual star series is an interpolation, not CMS data. Ratings determine quality bonus payments and rebate percentages.

Quality bonus payment#

The 5% county benchmark increase paid to MA contracts rated 4.0 stars or higher (with double bonuses in some counties). Because bonus status also raises the rebate share a plan can spend on supplemental benefits, crossing — or falling below — the 4.0 threshold moves real benefit-funding money. Star changes hit QBP revenue roughly two years after the rating year.

MOOP#

Maximum out-of-pocket: the annual cap on what an MA member can pay in cost sharing for in-network Medicare-covered services. CMS sets the allowable maximum each year; plans compete by setting lower voluntary MOOPs. Original Medicare has no MOOP — a key MA selling point.

MFP (maximum fair price)#

Maximum fair price: the ceiling price negotiated by CMS under the Inflation Reduction Act for selected high-spend drugs. The first 10 negotiated prices took effect January 2026 for Part D. The MFP resets net-price benchmarks class-wide, because payers anchor formulary negotiations for competitor drugs to it.

D-SNP#

Dual-eligible Special Needs Plan: an MA plan type restricted to people enrolled in both Medicare and Medicaid. D-SNPs carry higher risk-adjusted revenue and Medicaid-integration requirements that vary by state.

C-SNP#

Chronic-condition Special Needs Plan: an MA plan restricted to beneficiaries with specific severe or disabling chronic conditions (most commonly diabetes, cardiovascular disease, or heart failure). Benefits and networks are built around the qualifying condition.

I-SNP#

Institutional Special Needs Plan: an MA plan for beneficiaries who live in — or need the level of care provided by — a skilled nursing or other institutional facility for 90+ days.

FIDE-SNP#

Fully Integrated Dual Eligible Special Needs Plan: a D-SNP in which a single organization holds both the Medicare contract and a Medicaid managed-care contract, integrating benefits, care management, and appeals. States without FIDE infrastructure carry higher integration lift for entrants.

V28 (CMS-HCC model)#

Version 28 of the CMS-HCC risk-adjustment model, phased in across payment years 2024–2026. V28 removed or reweighted thousands of diagnosis codes, cutting MA risk-score revenue relative to the prior model — a major driver of the 2025–2026 benefit cuts and market exits.

CPSC files#

The CMS monthly "Monthly Enrollment by Contract/Plan/State/County" files: the source of record for county-level MA enrollment by plan. CPSC underlies this site's county pages and the planned HHI concentration work.

HHI#

Herfindahl-Hirschman Index: the sum of squared market shares, from near 0 (fragmented) to 10,000 (monopoly). DOJ/FTC treat markets above 2,500 as highly concentrated. State-level MA HHI pages are on this site's roadmap, pending the full-county CPSC pipeline.

PMPM#

Per member per month: a normalized dollar amount per enrollee, used to compare revenue, cost, or benefit value across plans and years regardless of enrollment size.

Velocity#

This site's momentum measure: the year-over-year change in MA penetration, in percentage points. A county at 52% penetration with +1.8 pts velocity is converting share faster than a flat county at 60%.

ANOC (Annual Notice of Change)#

The Annual Notice of Change: the document every MA and Part D member receives by late September stating exactly what changes in their plan for the coming January, including premium, cost sharing, benefits, and formulary. The ANOC is the single biggest switch trigger of the year; members who read a bad one arrive at AEP already looking.

AEP (Annual Enrollment Period)#

The Annual Enrollment Period, October 15 to December 7 each year: the window in which any Medicare beneficiary can join, switch, or drop an MA or Part D plan effective January 1. AEP is the peak selling season and the period this site's contestable-member and territory-planning pages are built around.

OEP (MA Open Enrollment Period)#

The Medicare Advantage Open Enrollment Period, January 1 to March 31: existing MA enrollees may make one change, to another MA plan or back to Original Medicare with a PDP. OEP is a second-chance window for winning members who regret an AEP choice, and a retention risk for plans that captured members on crosswalk defaults.

SEP (Special Enrollment Period)#

A Special Enrollment Period: the right to change plans outside the standard windows, triggered by qualifying events such as moving, losing coverage, or a plan termination. Dual-eligible and Low-Income Subsidy beneficiaries hold a recurring SEP under current CMS rules, which makes that population sellable year round rather than only during AEP. Verify the current SEP rules in CMS guidance before building outreach on them.

LIS (Low-Income Subsidy / Extra Help)#

The Part D Low-Income Subsidy, also called Extra Help: reduces premiums and cost sharing for qualifying low-income beneficiaries. LIS status matters to sales teams because it carries a recurring SEP and identifies members eligible for D-SNP or LIS-benchmark products.

Disenrollment rate#

The share of a contract's enrollment that leaves the plan during the year. CMS publishes contract-level disenrollment rates annually in a public file, splitting voluntary from involuntary moves. High voluntary disenrollment signals member dissatisfaction and is a churn-vulnerability flag when selling against an incumbent. Ingestion of this file is on this site's roadmap.

Runway score#

This site's modeled index of remaining MA growth room in a geography: penetration gap (distance to the highest observed penetration in the tracked set) multiplied by velocity and by the Original Medicare base, normalized so the top geography scores 100. A MedicareInsights index, never citable as CMS data. Geographies under 50% penetration are classed as conversion markets; 50% and above as switcher markets.

Crosswalk#

The CMS process that maps members of a terminated plan into a successor plan by default. Members can shop instead; those who accept the crosswalk often absorb premium or benefit changes without an active choice — which is why crosswalked membership is a retention risk flag.

Where the numbers come from

Every term above appears in context on the answer pages with its source and vintage. For the full source registry, methods, and limitations, see methodology & sources.