Codes and Frequencies
For sample adults and sample children (and, prior to 2019, persons) who do not currently have any kind of health care coverage, HILAST indicates how long it has been since the person had any kind of health care coverage.
According to the Field Representative's Manual for 1997 forward, the question associated with HILAST, "When was the LAST time [person] had health care coverage?", is asked only for persons who report currently having no health insurance coverage of any kind (or, for 2000 forward, only a single service plan).
Thus, throughout the period, HILAST is not asked of people who report having health insurance coverage via any of the following: private health insurance, including Medi-Gap; Medicare; Medicaid; Children's Health Insurance Program; Military health insurance (including Military Health Care/VA and TRICARE/CHAMPUS/CHAMP-VA); Indian Health Service; State-sponsored public health care coverage plans; and other government programs.
For 2000 forward, HILAST is also asked of people reporting only single service plan coverage.
During the course of data editing, the National Center for Health Statistics (NCHS) discovered many errors in the responses to questions about insurance coverage.
Often, respondents misclassified the type of insurance they had. 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 card provided by the interviewer. Accordingly, the NCHS created a series of recoded insurance variables. For these recoded insurance variables, the data are back-edited, taking into account such factors as the proper classification of the verbatim names of insurance plans and responses to questions about why insurance coverage had stopped.
Because of the errors in respondents' original (unedited) answers to questions about insurance coverage, the NCHS warns that "the variables HILAST and HINOTYR, which reflect periods of non coverage, cannot be used to estimate the rate of uninsurance." Instead, the NCHS recommends using the health insurance recodes, estimating the rate of uninsurance as a residual.
The relevant health insurance recodes in IPUMS NHIS are:
HIHSE (Covered by Indian Health Service: Recode); HIMILITE (Covered by military health insurance: Recode); HIMCAIDE (Covered by Medicaid: Recode);
HIMCAREE (Covered by Medicare: Recode);
HICHIPE (Covered by Children's Health Insurance Program: Recode);
HISTATEE (Covered by other state-sponsored health plan: Recode);
HIOTHGOVE (Covered by other government program: Recode)
HINOTCOVE (No insurance coverage)
In the survey for 1997 forward, interviewers first asked, "Are you covered by health insurance or some other kind of health care plan?"
Respondents were instructed to "Include health insurance obtained through employment or purchased directly as well as government programs like Medicare and Medicaid that provide medical care or help pay medical bills." In 1997-2003 the survey form instructed interviewers to only read the preceding statement "if necessary."
Individuals who had an affirmative response to the preceding question were asked, "What kind of health insurance or health care coverage do you have?" Respondents selected the appropriate response from a card listing various types of insurance coverage.
The choices included:
- 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)
- Medicare (1997 forward)
- Medi-Gap (1997 forward)
- Medicaid (1997 forward)
- CHIP (Children's Health Insurance Program) (1999 forward)
- Military Health Care/VA (1997-2003)
- Military Health Care (CHAMPUS/TRICARE/CHAMP-VA) (1997-2018)
- Military related health care: TRICARE (CHAMPUS)/VA health care/CHAMP-VA (2019 forward)
- Indian Health Service (1997 forward)
- State-sponsored health plan (1997 forward)
- Other government program (1997 forward)
- Single Service Plan (e.g., dental, vision, prescriptions) (1999 forward)
- No coverage of any type (2000 forward)
Respondents could pick more than one type of insurance and interviewers were instructed to mark all that applied.
Respondents were consistently instructed to exclude private plans that "only provide extra cash while hospitalized." In 1997-1998 respondents were also instructed to "EXCLUDE private plans that ... pay for only one type of service (nursing home care, accidents, or dental care)." Beginning in 1999, "Single Service Plan" was added as a possible response, and, consequently, the instructions were changed to read, "INCLUDE those [private plans] that pay for only one type of service (nursing home care, accidents, or dental care)."
In follow-up questions, interviewers recorded the names of up to four private health insurance plans. If the person was reported as covered by CHIP (beginning in 2000), by a state-sponsored health plan, or by another public program (other than Medicaid) that paid for health care, the interviewer recorded the name of that plan. The placement and wording of these questions about the names of specific government health care plans varied across years.
For persons initially reported as not having health care coverage of any kind, interviewers asked, in sequence, whether the person had Medicare coverage, Medicaid coverage, coverage via a Medicaid program or non-Medicaid state-sponsored health insurance program with the appropriate name for the state, CHAMPUS or CHAMPVA coverage, or any private insurance. For those who acknowledged any such coverage, the interviewer repeated the series of questions mentioned above to determine the specific type of coverage. Those who did not acknowledge any such coverage were asked the question associated with HILAST, namely, "When was the last time you had health care coverage?"
For 1997-1999, the NHIS instrument reconfirmed that the person had no health insurance of any kind by asking, "Just to verify, does [person] have Medicare, Medicaid, CHIP (Children's Health Insurance Program), CHAMPUS or CHAMPVA, or any private insurance?" If the answer was "no," then the respondent was asked the question associated with HILAST. However, for 2000 forward, this verification question was not asked.
As noted in the description of this variable, the NCHS warns that HILAST "cannot be used to estimate the rate of uninsurance."
The variable is largely comparable for 1997 forward with four exceptions:
- Questionnaire changes introduced in 2019 may limit comparability with earlier years. 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.
- Response categories have changed over time with response categories remaining the same from 1997-2015, 2016-2018, and 2019 forward, with differences between each of those time periods. Because the intervals used to record respondents' answers varies over time, IPUMS NHIS uses a composite coding system for HILAST to maximize comparability. The first digit identifies time periods which can be identified in all years: 1 year or less (code 1), 1 to 3 years (code 2), 3+ years (code 3), Never (code 4), and unknown (code 9). The second and third digits identify periods specified for only a subgroup of years. However, users should be aware of how changes in the exclusive and inclusive nature of response categories impacts the comparability of the composite coding scheme. For example, for 2019 forward, all response categories are inclusive of the smaller year and exclusive of the larger year (i.e., "1 year or more, less than 2 years"). However, for 1997-2015, all response categories are exclusive of the smaller year and inclusive of the larger year (i.e., "More than 1 year, 3 years or less"). Therefore, someone who last had insurance exactly one year ago could be coded to "23 - 1 year or more, less than 2 years" in 2019, but could be coded to "13 - More than 6 months, 1 year or less" in 1997-2015. This is important if users choose to use only the first digit of the code, since someone who indicates it has been one year since they last had health insurance could be collapsed into the "2" category in 2019, but the "1" category in 1997-2015. Users concerned about this level of detail may consider retaining all of the detailed codes instead of only looking at the first digit. Please see the codes tab for the availability of each response category.
- 2000-2018: In contrast to 1997-1999, there is no verification question asked, and the NHIS instrument explicitly instructs that the question associated with HILAST be asked of people reporting only single service plan coverage.
- 1997-1999: As noted above, in this period the NHIS instrument reconfirms that a person has no health insurance of any kind by asking the respondent, "Just to verify, does [person] have Medicare, Medicaid, CHIP (Children's Health Insurance Program), CHAMPUS or CHAMPVA, or any private insurance?" If the answer is "no," then the respondent is asked the question associated with HILAST.
Throughout the period 1997 forward, the question associated with HILAST is not asked of persons who report having health insurance coverage via any of the following: private health insurance, including Medi-Gap; Medicare; Medicaid; Children's Health Insurance Program; Military health insurance (including Military Health Care/VA and TRICARE/CHAMPUS/CHAMP-VA); Indian Health Service; State-sponsored public health care coverage plans; and other government programs.
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.
- 1997-1999: Persons without health insurance coverage.
- 2000-2018: Persons without health insurance coverage or whose only health insurance is a single service plan.
- 2019: Sample adults age 18+ and sample children age 0-17 without health insurance coverage.