Finding Medicare Enrollment Statistics

January 12, 2017 – March 19, 2021 R44735

Finding Medicare Enrollment Statistics
Updated March 19, 2021
Congressional Research Service
https://crsreports.congress.gov
R44735

Finding Medicare Enrollment Statistics

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.
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 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.
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Table 1. Selected Sources for Medicare Enrollment Statistics
(“+” indicates the statistic is included in the source; “—” indicates the statistic is not included in the source.
Click on each source to navigate to full details in the report.)
Total
Coverage Type
Geographic Area
Beneficiary Type
Original
Total
Medicare
Cong.
Source
Enrollment
A
B
C
D (A and/or B) National State
Territorya County District Aged Disabled
Currency
Medicare
AS, GU,
Delay of 1-
Enrollment
+
—
— +
+
+
+
+
+
—
+
+
MP, PR, VI
2 months
Dashboard
CMS Program
+
AS, GU,
Previous
+
+
+
—
+
+
+
—
—
+
+
Statistics
MP, PR, VI
Year
Previous
CMS Fast Facts
+
—
—
+
+
+
+
—
—
—
—
+
+
year
Congressional
Previous
—b
—
—
+
+
+
+
+
PR, VI
+
+
—
—
District Report
Yearc
Medicare
Advantage/Part
AS, GU,
Delay of 1
—b
—
—
+
+
—
—
+
+
—
—
—
D Contract and
MP, PR, VI
month
Enrollment Data
Medicare
No longer
Enrollment
+
+
+
— —
+
+
+
PR, VI
+
—
+
+
updatedd
Reports
Medicare Board
Previous
of Trustees
+
+
+
+
+
+
+
—
—
—
—
+
+
year
Annual Report
Source: Compiled by the Congressional Research Service (CRS).
Notes: Not all data sources in this report are represented in this table. For information on topics such as dual-eligible populations and Medigap, see the sources below.
a. Territory abbreviations: American Samoa (AS), Guam (GU), Northern Mariana Islands (MP), Puerto Rico (PR), and Virgin Islands (VI).
b. Does not include “total enrollment,” but instead indicates total “Medicare eligible.”
c. Data updated each July since 2016.
d. Last updated with CY2012 data but remains the only publicly available source for county-level data on Part B enrollment.
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Finding Medicare Enrollment Statistics

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.
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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
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Finding Medicare Enrollment Statistics

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.
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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.

Author Information

Michele L. Malloy

Research Librarian

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Finding Medicare Enrollment Statistics

Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
shared staff to congressional committees and Members of Congress. It operates solely at the behest of and
under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not
subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in
its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or
material from a third party, you may need to obtain the permission of the copyright holder if you wish to
copy or otherwise use copyrighted material.

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