Purpose and Scope

No single source for Medicare enrollment statistics exists. This report describes various sources that present different breakdowns of Medicare enrollment data, including by coverage type (Part A, Part B, Part C, and Part D), geographic area, and beneficiary type (aged, disabled). The report provides guidance on determining the most current sources for different categories of enrollment data.

This report also presents basic categories and definitions for terms related to Medicare enrollment data, a quick reference table that summarizes key data available in selected resources, and a more detailed overview of core resources.

Categories and Definitions

This section provides basic definitions of Medicare coverage and beneficiary types to aid users in identifying the most useful sources for their needs. Because different sources may use various terms and abbreviations to refer to the same data, this section also includes commonly used synonyms for different types of Medicare coverage.

• Total Enrollment: Includes all beneficiaries (aged and disabled) and all Medicare parts (A, B, C, D).
• Enrollment in (Type of Coverage): Beneficiaries may be enrolled in more than one part of Medicare. Most persons aged 65 or older are automatically entitled to premium-free Part A based on their payment of Medicare payroll taxes, whereas other parts are voluntary.

• Part A: Provides coverage for inpatient hospital services, posthospital skilled nursing facility (SNF) services, hospice care, and some home health services. May be referred to as HI (hospital insurance).

• Part B: Provides coverage for physicians' services, outpatient hospital services, durable medical equipment, and other medical services. Beneficiaries voluntarily enroll and pay premiums. May be referred to as SMI (supplementary medical insurance).

• Original Medicare: Refers to Parts A, B, or both. Also called FFS (fee-for-service).

• Part C: Private insurance option that covers all Parts A and B services, except hospice. Also called MA (Medicare Advantage), Medicare Managed Care, or formerly Medicare+Choice.

• Part D: Provides coverage of outpatient prescription drugs through optional enrollment and premium payments. May be provided through private prescription drug plans (PDPs) or through Medicare Advantage prescription drug plans (MA-PD plans). Note that some Part D enrollees receive subsidies, either low-income subsidies or the Retiree Drug Subsidy, due to employer-based retiree drug coverage.

• Enrollment in (Geographic Area): National, state, territory, county, or congressional district.
• Enrollment for (Beneficiary Type): Beneficiaries become eligible for Medicare based on age or disability.
• Dual-Eligible Enrollment: Available to individuals who qualify for both Medicare and Medicaid. These enrollees may be aged or disabled beneficiaries, and may qualify for full or partial Medicaid benefits. Also called dual enrollment.
• Medigap Enrollment: Beneficiaries can optionally enroll in private individual insurance policies that supplement original Medicare. These plans are standardized and identified by plan letter (Plans A-N). Also called Medicare Supplemental Insurance.

For more background information on Medicare, please see CRS Report R40425, Medicare Primer, coordinated by Patricia A. Davis.

Selected Sources for Medicare Enrollment Statistics

This section provides detailed information on core sources for Medicare enrollment statistics and includes links to each source. Table 1 summarizes key data available in selected sources. Not all data sources identified in this report are represented in the table. For example, for information on dual-eligible populations, see the "Medicare-Medicaid Coordination Office: Analytic Reports and Data Resources" section, and Medigap, see the "America's Health Insurance Plans" section below.

Centers for Medicare & Medicaid Services

The Centers for Medicare & Medicaid Services (CMS) is part of the Department of Health and Human Services (HHS) and administers programs such as Medicare, Medicaid, the Children's Health Insurance Program (CHIP), and the Health Insurance Marketplace. CMS sites and reports are the primary sources for Medicare enrollment data.

Medicare Enrollment Dashboard

https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/CMSProgramStatistics/Dashboard

Based on CMS administrative data, the dashboard provides monthly enrollment numbers for the most recent 12 months and annual data since 2011. Maps and charts (see Figure 1 for an example) are created according to user selections, such as geographic areas (national, state, county) or coverage type (Hospital/Medical by Original Medicare, Medicare Advantage and Other, Total, and Prescription Drug). Note that it does not provide breakdowns by Part B or congressional district.

At the time of this update, the interactive map functionality of the dashboard is unavailable, but CMS continues to post monthly enrollment data on the website in "Medicare Enrollment Dashboard Datafile," a zip file format.

Figure 1. Medicare Enrollment Dashboard

Source: Centers for Medicare & Medicaid Statistics.

CMS Program Statistics

https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/CMSProgramStatistics

The portal links to CMS administrative data on Medicare enrollment since 1985, including annual trends, demographic breakdowns, maps, state tables, enrollment in Medicare Advantage and other health plans, newly enrolled beneficiaries, Medicare deaths, and Medicare-Medicaid dual enrollment. These data are posted annually. This replaces but still refers to the Medicare and Medicaid Statistical Supplement, which was published from 2001 to 2013. For earlier statistics, see the "Historical Enrollment Data" section.

CMS Fast Facts

https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/CMS-Fast-Facts/

The quick reference statistical summary on annual CMS program and financial data includes a simple table with national enrollment data on Medicare and Medicaid.

Congressional District Report

https://www.cms.gov/Medicare/Prescription-Drug-Coverage/PrescriptionDrugCovGenIn/index.html

The Congressional District Report provides 2016-2020 enrollment by congressional district for Original Medicare, Part C, Part D, and Medicare Retiree Drug Subsidy.

To view the most recent data, go to the Prescription Drug Coverage page and download the "2020 Congressional District Report" zip file, found at the top of the "Downloads" section. Open the third file (entitled "2020 Congressional District Report_20.12.10.xlsx"). Navigate the tabs to access MA (Part C), FFS (Original Medicare, i.e., Part A and/or Part B), and Part D enrollment for each congressional district. The data are organized by state and include state totals. It does not include "total enrollment," but instead lists enrollment by type and "Medicare eligible."

Previous years' zip files are also available for download.

Medicare Advantage/Part D Contract and Enrollment Data

https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/MCRAdvPartDEnrolData/index.html

The website provides detailed information on Part C and Part D, including enrollment in specific plans or plan types (HMO, PPO, MSA, etc.) by state and county. It does not include "total enrollment," but instead lists enrollment by type and "Medicare eligible." The information has a one-month lag, compared to a one- to two-month lag on the "Medicare Enrollment Dashboard." Please note that data are accessible through Excel files and require some manipulation.

Medicare Enrollment Reports

An alternative CMS data source, Medicare Enrollment Reports, includes more granular data not currently available through the "Medicare Enrollment Dashboard." The Medicare Enrollment Reports is the only source to provide enrollment information by county for Part B. The most recent data in this format are from July 2012. The table break down enrollment by state, and then distinguish among enrollment in Part A and/or B, A only, B only, and A and B.

Applicable data are found in the following table:

• "Medicare Enrollment: Aged and Disabled by State and County, July 2012," at https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/MedicareEnrpts/Downloads/County2012.pdf.

Medicare-Medicaid Coordination Office: Analytic Reports and Data Resources

https://www.cms.gov/Medicare-Medicaid-Coordination/Medicare-and-Medicaid-Coordination/Medicare-Medicaid-Coordination-Office/index.html

The portal links to several reports with enrollment data for dual-eligible Medicare-Medicaid beneficiaries. These include annual reports to Congress, the State Data Resource Center, and analytic reports addressing national, state, and county-level trends. Data and statistical reports can be found on the website's Data & Statistical Resources page, https://www.cms.gov/Medicare-Medicaid-Coordination/Medicare-and-Medicaid-Coordination/Medicare-Medicaid-Coordination-Office/DataStatisticalResources/Data-and-Statistical-Resources.

CMS Office of Legislation Contact Information

https://www.cms.gov/About-CMS/Agency-Information/CMSLeadership/Office_OL.html

For more information on Medicare enrollment data, congressional staff may directly contact the CMS Office of Legislation. The CMS Congressional Affairs Group Director is Maria Martino (202-690-8220, Maria.Martino@cms.hhs.gov).

Medicare Board of Trustees

Members of the Medicare Board of Trustees oversee financial operations of the Hospital Insurance (HI) and Supplementary Medical Insurance (SMI) trust funds. The board, in collaboration with the CMS Office of the Actuary, prepares a report each summer.

Medicare Board of Trustees Annual Report

https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/ReportsTrustFunds/index.html

The Trustees Report includes national enrollment trends and projected enrollment by part (A, B, C, D). The report also includes breakdowns of Part D enrollment by subsidy type (low-income subsidies and the Retiree Drug Subsidy) and ratios of Part C to total Medicare enrollment. Specific enrollment tables for the most recent report include the following:

• "Table II.B1. Medicare Data for Calendar Year 2019" (p. 10 of the 2020 Annual Report) includes general enrollment breakdowns by part (A, B, D), beneficiary type (aged, disabled), and in total.
• "Table IV.B7. Part D Enrollment" (p. 140 of the 2020 Annual Report) includes both enrollment statistics and projections for 2010-2029. The table also includes breakdowns of enrollment by subsidy type.
• "Table IV.C1. Private Health Plan Enrollment" (p. 150 of the 2020 Annual Report) includes Part C enrollment and projections for 2010-2029. The table also includes ratios of Part C to total Medicare enrollment.
• "Table V.B3. Medicare Enrollment" (p. 176 of the 2020 Annual Report) includes enrollment statistics and projections for 1970-2094 by part and in total.

Medicare Payment Advisory Commission

The Medicare Payment Advisory Commission (MedPAC) is a nonpartisan legislative branch agency that provides Congress with analysis and policy advice on the Medicare program and issues reports on specific Medicare-related topics.

MedPAC Reports

http://www.medpac.gov/-documents-/reports

MedPAC issues two standard reports to Congress each year. The Medicare Payment Policy report is released in March and the Medicare and the Health Delivery System report is released in June. Basic chapters are consistent each year, but others reflect policy areas of interest and mandated reports. Additional stand-alone reports are sometimes issued as required by Congress or at the direction of MedPAC.

In some chapters, enrollment data from the Medicare Board of Trustees Annual Report or CMS enrollment files are presented and accompanied by analysis. Within the most recent Medicare Payment Policy report, the Medicare Advantage (Part C) chapter provides enrollment tables.

Data Book: Health Care Spending and the Medicare Program

http://www.medpac.gov/-documents-/data-book

The portal provides access to the most recent tables and graphs describing the Medicare program, including enrollment by beneficiary demographics.

America's Health Insurance Plans

America's Health Insurance Plans (AHIP) is the health insurance community's national trade association. As an advocacy group, it compiles statistics and issues reports.

CMS does not track Medigap enrollment, but AHIP provides a report on the topic.

State of Medigap: Trends in Enrollment and Demographics
https://www.ahip.org/wp-content/uploads/AHIP_State_of_Medigap-2020.pdf

The report describes Medigap coverage options, demographics of enrollees with Medigap policies, and the most recent enrollment trends by using the latest available data sources: the 2018 National Association of Insurance Commissioners (NAIC) data, the 2018 California's Department of Managed Health Care data, and the 2017 Medicare Current Beneficiary Survey (MCBS) results. It includes enrollment data by plan (A-N) and state and territory.