Contents

• Purpose and Scope
• Federal Data Sources
• Centers for Medicare & Medicaid Services (CMS): National and State Data
• Medicaid and CHIP Payment and Access Commission (MACPAC): National and State Data
• Congressional Budget Office (CBO): National Data and Projections
• Census Bureau American Community Survey (ACS): National, State, and Local Data
• National Center for Health Statistics (NCHS) Data Query System: National Data
• Nonfederal Data Sources
• KFF: National, State, and Congressional District Data
• Congressional District Health Dashboard: State and Congressional District Data
• Center on Budget and Policy Priorities (CBPP): State and Congressional District Data
• State Health Compare: National and State Data
• State Resources: State and Local Data

Purpose and Scope

Medicaid is a means-tested entitlement program that finances the delivery of primary and acute medical services, as well as long-term services and supports (LTSS). Each state designs and administers its own Medicaid program within federal parameters. Medicaid is jointly financed by states and the federal government.¹

This report identifies selected resources for national, state, and local-level (i.e., congressional district or county level) data on Medicaid enrollment and enrollee characteristics that are frequently evaluated when examining Medicaid policy options. This report is not intended to be fully comprehensive. The descriptions and websites below include information on statistics, methodology, sources, definitions, caveats, and currency. CRS did not independently evaluate the accuracy of any of these data. Most of the data resources presented are from federal entities. Some are produced by think tanks and advocacy organizations. CRS does not take positions on policy options or any policy recommendations advocated by these organizations. References to think tank and advocacy organizations data sources are included solely for informational purposes.

Table A-1 in the Appendix of this report provides key sources of data, organized based on the types of information they include, to guide readers in selecting appropriate data sources for different inquiries. Congressional offices may request assistance from CRS regarding data questions or additional search assistance.

Data from different sources might not be comparable. For example, sources may use data from different periods of time (e.g., fiscal year vs. calendar year). Sources may also use different measures for enrollment; for example, an "average monthly" enrollment number would be lower than a total of all individuals who were "ever enrolled" at any point during an entire year.

Additionally, some sources rely on survey data, some sources rely on administrative data, and some sources base their estimates on analyses of both types of data. Surveys generally rely on self-reported health insurance coverage, and respondents may under-report receipt of government benefits such as Medicaid.² Survey data are also subject to sampling error, as estimates are based on a sampling of the population. Administrative data are produced by the federal and state government agencies that operate the Medicaid program, generally as a by-product of program administration; they may include data from enrollment rolls maintained by state Medicaid agencies. Administrative data are generally considered more accurate than survey data, but are often restricted to information needed to administer the program. Surveys might collect other types of information of interest to researchers and to Congress, such as health and demographic information.

A frequently requested type of data is enrollment by eligibility group, particularly those eligible through the Patient Protection and Affordable Care Act (ACA, P.L. 111-148 as amended) Medicaid expansion that was implemented at state option starting in 2014.³ The ACA Medicaid expansion is the most recent major expansion of Medicaid eligibility, and it covers nonelderly adults (under age 65) whose modified adjusted gross income is under 133% of the federal poverty level (FPL) (effectively 138% of FPL with an income disregard of 5% of FPL). The three major categories of nonelderly adults that would qualify for the ACA Medicaid expansion are adults without dependent children, parents with dependent children, and adults with disabilities. Prior to the ACA Medicaid expansion, a few states provided Medicaid coverage to adults without dependent children, and in general, the Medicaid income eligibility level for parents and adults with disabilities was significantly lower than 133% of FPL (i.e., the ACA Medicaid expansion eligibility level). Not all states have adopted the ACA Medicaid expansion.

Some sources included provide historical enrollment data. For context about trends in Medicaid enrollment over time, see "Medicaid Enrollment" in CRS Report R43357, Medicaid: An Overview.

Some federal websites referenced in this report may be undergoing changes or be inaccessible as agencies comply with recent executive orders, guidance from the Office of Management and Budget (OMB), and Secretarial orders. Additionally, it is unclear at the time of writing what the impact of proposed Department of Health and Human Services restructuring⁴ may be on certain federal agency data sources.⁵

Federal Data Sources

Centers for Medicare & Medicaid Services (CMS): National and State Data

CMS administers the Medicaid program at the federal level and produces several enrollment data resources, including the following:

• Medicaid & CHIP [State Children's Health Insurance Program] Enrollment Data Highlights shows CMS's most recent available national monthly Medicaid enrollment number, based on state-reported administrative data.⁶ This shows total Medicaid enrollment in each state, but it does not show enrollment by eligibility group. Scroll down and click the map for state-level numbers.
• Medicaid Enrollment Data Collected Through MBES (Medicaid Budget and Expenditure System) has quarterly releases of state-reported monthly administrative data on "Total Medicaid enrollees" and "Total VIII Group" enrollees. The VIII Group, also known as the "New Adult Group," consists of adults enrolled through the ACA Medicaid expansion.⁷ (For national data, see the "Totals" row in the "State" column.
• Medicaid & CHIP Data Products include "Beneficiary Profiles" with national data on enrollee numbers, demographics, and health status. The data are based on a variety of administrative and survey sources. The frequency of publication may vary.
• Transformed Medicaid Statistical Information System (T-MSIS) Analytic Files (TAF) has demographic and eligibility information for enrollees. Scroll down this page to view "Data briefs" on various enrollee characteristics (e.g., primary language and disability). National and state Medicaid enrollment by month and year appear under "Enrollment data tables." T-MSIS is an administrative data source; the frequency of data releases may vary.

Medicaid and CHIP Payment and Access Commission (MACPAC): National and State Data

MACPAC is a nonpartisan legislative branch agency that provides policy and data analysis. MACPAC's annual MACStats publication includes several state and national enrollment tables, drawing on multiple data sources. For example, the MACStats December 2024 edition includes the following national enrollment measures:

• Exhibit 1, Medicaid and CHIP Enrollment as a Percentage of the U.S. Population has national Medicaid enrollment estimates both as a total number and as a share of the population.⁸
• Exhibit 10, Medicaid Enrollment and Total Spending Levels and Annual Growth has national Medicaid enrollment levels since FY1973. A similar historical table going back to FY1966 (when Medicaid started) is in MACStats, 2017 Edition. These tables provide average monthly enrollment over the year (also known as full-year equivalent).
• Exhibit 7, Medicaid Beneficiaries (Persons Served) by Eligibility Group shows the annual numbers of Medicaid beneficiaries by eligibility group: children, adults under 65, adults over 65, and persons with disabilities, since FY1975.⁹

Examples of national data tables on enrollee characteristics, based on MACPAC analyses of survey data, include the following:

• Exhibit 2, Characteristics of Non-Institutionalized Individuals by Age and Source of Health Coverage.
• Exhibit 39, Coverage, Demographic, and Health Characteristics of Non-Institutionalized Individuals Age 0–18 by Primary Source of Health Coverage.
• Exhibit 44, Coverage, Demographic, and Health Characteristics of Non-Institutionalized Individuals Age 19-64 by Primary Source of Health Coverage.

MACStats includes several state-level enrollment tables. For example, the December 2024 edition includes the following:

• Exhibit 14, Medicaid Enrollment by State, Eligibility Group, and Dually Eligible Status shows the numbers of Medicaid enrollees ever enrolled during the fiscal year in each state by eligibility group: children, "new adult" enrollees under the ACA Medicaid expansion, other adults under age 65, "aged" adults over 65, and individuals with disabilities.¹⁰ It also breaks out "dually eligible" enrollees, who are enrolled in both Medicaid and Medicare.
• Exhibit 15, Medicaid Full-Year Equivalent Enrollment by State and Eligibility Group shows Medicaid enrollment by state and eligibility group as measured by full-year equivalent, which is the average monthly enrollment.

The Technical Guide to MACStats provides information about data methods and sources.

Congressional Budget Office (CBO): National Data and Projections

CBO periodically (at least once a fiscal year) produces Medicaid "Baseline Projections" that include national average monthly enrollment estimates by eligibility category: Aged, Blind and Disabled, Children, Adults—traditional eligibility categories, and Adults—made eligible by the ACA. They also include future "average monthly" and "ever enrolled" enrollment projections, assuming current federal law. See CBO's Processes page for more about its methodologies and analyses.

Census Bureau American Community Survey (ACS): National, State, and Local Data

The U.S. Census Bureau's American Community Survey (ACS) annually produces national, state, county-level, and congressional district estimates of Medicaid/Means-Tested Public Coverage, which includes Medicaid, CHIP, and certain state-specific programs for low-income or high-risk uninsured individuals.

National and state enrollment estimates since 2008 are in these spreadsheets:

• HIC-4_ACS, Health Insurance Coverage Status and Type of Coverage by State—All Persons.
• HIC-5_ACS, Health Insurance Coverage Status and Type of Coverage by State—Children Under 19.
• HIC-6_ACS, Health Insurance Coverage Status and Type of Coverage by State—Persons Under 65.

The Data.Census.gov tables linked below can be used to produce estimates of enrollment at various local levels. The table links reflect the most current available at the time of publication and default to one-year estimates at the national level. Select "all geographies" under the geography filter and pick the desired geographical designation (e.g., county, congressional district, city) to show estimates at a local level. Specific years and estimate types (one-year or five-year) can be changed by selecting the caret next to the table title.

In general, one-year estimates are more current, but five-year estimates have smaller margins of error and are available for more geographies. See the Census Bureau's Using 1-Year or 5-Year American Community Survey Data.

Examples of ACS Tables that estimate Medicaid enrollment include the following:

• ACS Table S2704, Public Health Insurance Coverage by Type and Selected Characteristics.
• ACS Table B27010, Types of Health Insurance Coverage by Age.
• ACS Table C27007, Medicaid/Means-Tested Public Coverage by Sex by Age.
• ACS Table C27012, Health Insurance Coverage Status and Type by Work Experience.

ACS is based on a rolling sample survey that collects data throughout the year. Respondents are asked about their health coverage "currently" at the time they complete the questionnaire.¹¹ The Census Bureau has further information on ACS methodology.

National Center for Health Statistics (NCHS) Data Query System: National Data

The Centers for Disease Control and Prevention's NCHS Data Query System (DQS) provides a way to view data from a variety of NCHS surveys in one tool. NCHS DQS can be used to view estimates on over 150 health topics; filter estimates by source, characteristic, or time period; and create custom charts and graphs. The frequency of NCHS data releases may vary.

For some health topics, data are available by type of "Health insurance coverage" under "Select a group," as in this example chart for rates of self-reported hypertension among nonelderly adults, by primary insurance type, including "Medicaid or other public," which includes Medicaid and certain other state programs.

Medicaid coverage among people younger than 65 years" is also among the "Topic" choices, as in this example chart of Medicaid coverage rates by age group 1984-2019.¹²

Users can learn more about DQS, access a user guide for instructions on using the tool, and explore the health topics page for more details about source information and data characteristics.

Nonfederal Data Sources

The sources included in this section use government data sources as well as their own analyses and methodologies to provide estimates of enrollment and enrollee characteristics that may not be easily available from federal sources.

KFF: National, State, and Congressional District Data

KFF¹³ analyzes Medicaid data from various administrative data and survey data sources. The frequency of KFF's data releases varies.

KFF produces sortable state tables in State Health Facts. For example, it includes a table of monthly Medicaid enrollment based on CMS's Medicaid and CHIP Applications, Eligibility Determinations, and Enrollment Data. KFF also analyzes other public and private data sources to produce several Medicaid enrollee demographic tables under Medicaid & CHIP and Health Coverage & Uninsured. Enrollee demographics in these tables include age, sex, and race/ethnicity. In a multistate table, data can be sorted by clicking a column header. Users can also create custom state reports. See About State Health Facts to learn more about the tool.

KFF's Congressional District Interactive Map: Medicaid Enrollment by Eligibility Group14 has interactive congressional district maps and a table estimating the share of the population enrolled in Medicaid, and the number of Medicaid enrollees with breakdowns by major eligibility group. These estimates rely in part on June 2024 enrollment data from MBES. KFF apportioned those enrolled at any point during June 2024 into congressional districts.¹⁵ See the Methods section of the publication.

Congressional District Health Dashboard: State and Congressional District Data

NYU Langone Health's Congressional District Health Dashboard¹⁶ has congressional district estimates for a variety of health-related metrics, including Medicaid enrollment. Estimates are shown as a percentage of a district's population. The Medicaid enrollment estimate is based on ACS survey data and CMS administrative data. Data release frequency depends on the availability of the source data. Data include enrollment estimates for the past quarter. See the methodology page. Users can also view data at the state level and compare districts.

Center on Budget and Policy Priorities (CBPP): State and Congressional District Data

CBPP's¹⁷ Program Participation Data Dashboard has state and congressional district estimates of Medicaid/CHIP enrollment. Data include a breakdown by age of enrollee and estimates for monthly enrollment for the most recent month available. To view data by congressional district, select the caret next to each state.

CBPP's Program Participation Data Dashboard also has state-level estimates for certain Medicaid/CHIP enrollee characteristics such as sex, rural county residence, and race/ethnicity.

CBPP's estimates are based on ACS survey data and CMS administrative data. See the Methodology and limitations. Data release frequency depends on the availability of the source data.

State Health Compare: National and State Data

State Health Compare, from the University of Minnesota's State Health Access Data Assistance Center (SHADAC)¹⁸, uses ACS survey data to provide annual national and state-level estimates of Medicaid/CHIP coverage among populations with various characteristics. Under "Breakdown," various characteristics, such as work status and education, can be selected. Of individuals with the selected characteristic, the tool provides estimates of the number and percentage whose "primary source of coverage" is Medicaid/CHIP, alongside other health coverage types. SHADAC assigns most persons aged 65+ to Medicare for their primary source of coverage, thus most Medicaid/CHIP data in this tool reflect the under-65 population. For more information, see About SHADAC's State Health Compare Tool and their Health Insurance Coverage Type measure.

State Resources: State and Local Data

Specific states' Medicaid websites and other state-specific sources may also have enrollment data. Examples of states that have posted congressional district-level Medicaid enrollment data include Arizona, California, Colorado, Illinois, Michigan, Oregon, Pennsylvania, and Virginia.

Appendix. Selected Medicaid Enrollment Data Sources

Table A-1 provides links to several of the resources discussed in this report and displays sources by the types of data they include.

Footnotes

1.	For background on Medicaid, see CRS In Focus IF10322, Medicaid Primer, and CRS Report R43357, Medicaid: An Overview.
2.	See, for example, Dong Ding, Benjamin D. Sommers, and Sherry A. Glied, "Unwinding And The Medicaid Undercount: Millions Enrolled In Medicaid During The Pandemic Thought They Were Uninsured," Health Affairs, vol. 43, no. 5 (May 2024), pp. 725-731, https://doi.org/10.1377/hlthaff.2023.01069; Robert Hest, Tracking the Medicaid Undercount in the 2021 ACS Coverage Data, State Health Access Data Assistance Center, January 30, 2023, https://www.shadac.org/tracking-medicaid-undercount-2021-acs-coverage-data; and National Center for Health Statistics, Division of Analysis and Epidemiology, The Linkage of National Center for Health Statistics Survey Data to Centers for Medicare & Medicaid Services Transformed Medicaid Statistical Information System Claims Data (2014-2019): Matching Methodology and Analytic Considerations, Hyattsville, MD, September 2024, https://www.cdc.gov/nchs/data/datalinkage/NCHS-CMS-TMSIS-Linkage-Methodology_1.pdf.
3.	See CRS Report R43564, The ACA Medicaid Expansion, and CRS In Focus IF10399, Overview of the ACA Medicaid Expansion.
4.	See HHS Press Release, HHS Announces Transformation to Make America Healthy Again, March 27, 2025, https://www.hhs.gov/press-room/hhs-restructuring-doge.html.
5.	Congressional offices may contact CRS if a reference is inaccessible.
6.	These data are also known as monthly State Medicaid and CHIP Applications, Eligibility Determinations, & Enrollment Data.
7.	The Group VIII group is named after Section 1902(a)(10)(A)(i)(VIII) of the Social Security Act, which defines this population. Most of these adults are considered "newly eligible." However, some states expanded Medicaid eligibility to certain adults prior to 2014; in these cases, some of the VIII Group members presented in the data are considered "not newly eligible."
8.	Includes estimates for ever-enrolled and point-in-time for FY2023, and point-in-time for calendar year 2023.
9.	Beneficiaries are enrollees for whom payments are made during the fiscal year.
10.	Some Medicaid enrollees with disabilities are not counted in the "Disabled" eligibility category. For example, some persons with disabilities qualify for Medicaid through the ACA Medicaid expansion, which might have different financial eligibility criteria than disability eligibility pathways in their state. See CRS Report R43564, The ACA Medicaid Expansion, and CRS Report R46111, Medicaid Eligibility: Older Adults and Individuals with Disabilities.
11.	Kevin C. Heslin, Health Insurance Coverage Measurement in Two Major Surveys, U.S. Census Bureau, September 4, 2024, https://www.census.gov/newsroom/blogs/random-samplings/2024/09/health-insurance-coverage-measurement.html.
12.	One can select different age ranges under "Select Subgroup." The chart note indicates that "Medicaid coverage includes people who had any of the following at the time of interview: Medicaid, other public assistance (through 1996), state-sponsored health plan (starting in 1997), or Children's Health Insurance Program [(CHIP) starting in 1999]. It includes those who also had another type of coverage in addition to one of these... Data for 2019 and beyond have not been fully evaluated for comparability with earlier years." This chart is based on NCHS's National Health Interview Survey (NHIS). NCHS also publishes an NHIS table on Long-Term Trends in Health Insurance Coverage with Medicaid coverage estimates since 1965 among persons younger than 65.
13.	More information about KFF as an organization is available at https://www.kff.org/about-us/.
14.	Rhiannon Euhus, Alice Burns, and Robin Rudowitz, Congressional District Interactive Map: Medicaid Enrollment by Eligibility Group, KFF, March 11, 2025.
15.	Email from Tammie Smith, Communications Officer, KFF, April 30, 2025.
16.	More information about the Congressional District Health Dashboard is available at https://www.congressionaldistricthealthdashboard.org/about.
17.	More information about CBPP as an organization is available at https://www.cbpp.org/about.
18.	More information about SHADAC as an organization is available at https://www.shadac.org/about-us.