For 1976-1989, plans that only provide extra cash while the person was hospitalized were considered to be health insurance. However, the Field Representative's Manuals for these years instructed interviewers to exclude other forms of single service plans, such as "[those covering] dread diseases (cancer, polio), plans that pay only for accidents, plans that pay only for dental bills, [and] "income maintenance" (which pay a fixed amount both in and out of the hospital). Interviewers were also instructed to exclude public programs, including Medicaid, Medicare, public welfare, "Crippled Children's Program," care given to military personnel, and veterans' benefits.

For 1976 to 1992, the survey questions on private insurance asked about coverage for hospital, surgeon or doctor's bills. For 1986 and 1989, the question also included coverage for dentists' bills. The1986 Manual defined dental coverage as "any insurance which pays all or part of a dentist's bill for any dental services other than oral surgery." The 1989 and 1992 Manuals noted that dental coverage had to be part of a comprehensive plan, and not a single service plan, to count. For 1989 and 1992, single service plans were not considered to be private health insurance.

For 1993 to 1996, the Manuals instructed interviewers to consider single service plans as a form of private health insurance.

For 1997 forward, private health care plans are any insurance other than public programs. Such plans may be provided in part or in full by an individual's employer or union, and they may also be purchased directly. For 1997-2018, respondents were asked what kind of health insurance they had and shown a flashcard that listed types of insurance coverage. For 2019 forward, interviewers read the listed types of insurance coverage. Respondents could pick more than one type of insurance, and interviewers were instructed to mark all that applied.

Beginning in 2004, the Field Representative's Manuals instructed interviewers to treat COBRA and TCC coverage as private insurance. The Manuals discussion of COBRA and TCC was as follows:

1976, 1980

• Is anyone in the family covered by hospital insurance, that is, a health insurance plan which pays any part of a hospital bill?

• Is anyone in the family now covered by a health insurance plan which pays any part of hospital, doctor or surgeon's bill?

• (Not counting Medicare) is anyone in the family now covered by a health insurance plan which pays any part of hospital, doctor or surgeon's bill?

• Health insurance can also be obtained privately or through a current or former employer or union. Was anyone in the family covered by private health insurance or by membership in a health maintenance organization in (month)?

• (Not counting the government health programs we just mentioned,) In (month) was anyone in the family covered by a private health insurance plan? Do NOT include plans that pay for ONLY ONE type of service, such as nursing home care or accidents.

• (Not counting the government health programs we just mentioned,) In (month) was anyone in the family covered by a private health insurance plan?

• Private health insurance (2004 forward)

• Private health insurance plan from employer or workplace (1997-2003)

• Private health insurance plan purchased directly (1997-2003)

• Private health insurance plan through a State or local government program or community program (1998-2003)

For 1997 to 1999, only persons with an affirmative answer to the initial question about having insurance have responses to follow-up questions about the type of health insurance and the details of coverage; for 1997 to 1999, those who did not answer the initial question affirmatively are coded NIU (not in universe) for follow-up questions on insurance characteristics. Beginning in 2000, the response "no insurance" was included as a valid response to the initial question. Thus, for 2000 forward, the universe for follow-up questions on insurance coverage type and details was "all persons" (including those with an affirmative response to HINONE or "no insurance").

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 categories on a flashcard. Beginning in 1997, plan names were used to back-edit responses to verify the accuracy of insurance type. (See the variable description for HINOTCOVE for a description of this back-editing process.)