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Codes and Frequencies

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For sample adults and sample children (and, prior to 2019, all respondents), HIMCAID indicates whether the respondent had Medicaid coverage. For 1990 to 1996, it reflects coverage during the previous month. For 1997 forward, it reflects coverage at the time of the survey.

Users who want to compare Medicaid coverage over time should review the variable description HIPUBCOV, which may more accurately capture all respondents who were covered by Medicaid.

Note that the universe changed between 1999 and 2000, although this should not affect affirmative responses for this variable. For 1997 to 1999, it reflects responses of all persons who already indicated they had some form of health insurance. For 2000 forward it reflects responses of all persons.

Various definitions for Medicaid were provided to respondents over time, but the changes in definition were not substantial. Medicaid was generally defined as a health insurance program which provides medical care for persons in need. The Field Representative's Manual for 1997 defined Medicaid as "a medical assistance program that provides health care coverage to low income and disabled persons. The Medicaid program is a joint federal-state program which is administered by the States."


Medicaid pays for medical assistance to low-income families with dependent children and to aged, blind, or permanently and totally disabled individuals with incomes insufficient to meet the costs of medical services. The program became law in 1965. Medicaid is administered by state agencies and is jointly funded by the federal, state, and, sometimes, local governments. Eligibility requirements for this means-tested program vary across states. Most recipients of public welfare income programs such as TANF (Temporary Assistance to Needy Families) and SSI (Supplemental Security Income) are eligible for Medicaid coverage. In some states, other persons qualify, such as needy unemployed persons who have children and who are not receiving cash assistance, and medically needy persons whose income and assets are too low to cover their medical costs. Many Medicaid recipients are residents of medical institutions, such as low-income elderly persons in nursing homes. Such institutionalized persons are not included in the NHIS sample, which covers the civilian, non-institutionalized population of the United States.

As the manuals noted, the name for the Medicaid program varies across states. Interviewers were supplied with cards listing "State Names for Medicaid, CHIP, State-/Local-Sponsored, and Other Health Insurance Programs" in their state. These linked broad categories of insurance that were studied in the survey to recognizable public health insurance program names. For example, in 1999, the California Medicaid program was called the "Medi-Cal" or "Medi-Cal Managed Care" or "The Two-Plan Model."

The definition, order and wording of private health insurance changed over time to reflect changes in the availability of different types of coverage and issues of interest. Users are strongly encouraged to review the user note Insurance Data Collection.

This variable is not comparable with the recoded variable HIMCAIDE, which reflects responses edited for accuracy by the NCHS. See the comparability tab for more details.


Apart from the universe changes and changes in reference period, this variable is mostly comparable over time. However, users should be aware that the responses for HIMCAID were not edited for accuracy, and therefore are not comparable with the recoded variable HIMCAIDE. HIMCAIDE has been edited for accuracy by the NCHS based on plan name. Substantial questionnaire changes introduced in 2019 may limit comparability with earlier years.


During the course of data editing, the NCHS discovered many errors in the responses to questions about insurance coverage. This might be shown, for example, by a mismatch between the verbatim name of an insurance plan and the type of insurance coverage the person selected from the categories on the card. Because of such errors in reporting, users should not combine the edited responses with the non-edited responses.

The NHIS questionnaire was substantially redesigned in 2019 to introduce a different data collection structure and new content. For more information on changes in terminology, universes, and data collection methods beginning in 2019, please see the user note.


  • 1990-1992: All persons.
  • 1993: All persons in quarters 3 and 4.
  • 1994-1995: All persons.
  • 1996: All persons in quarters 3 and 4.
  • 1997-1999: Persons covered by some type of health plan.
  • 2000-2018: All persons.
  • 2019-2022: Sample adults age 18+ and sample children age 0-17.


  • 1990-2022