National Health Interview Survey
The National Health Interview Survey (NHIS) is an ongoing survey conducted throughout the year by the National Center for Health Statistics to monitor the health of the nation. It has been conducted since 1957. The NHIS data are collected through an in-person survey using computer-assisted personal interviewing (CAPI) in households. The target universe is defined as all dwelling units in the civilian non-institutionalized population in the U.S.
The NHIS consists of a Basic Module, including the Family Core, the Sample Adult Core, and the Sample Child Core, as well as several supplements that vary from year to year. In recent years slightly less than 35,000 households were interviewed. The NHIS uses an area probability sample frame, based on the preceding decennial Census, with independent address lists obtained explicitly for the NHIS.
The sample for the NHIS represents the 50 states and the District of Columbia. However, the lowest level of geography available in the public-use data files is Census region. The household response rate is about 90 percent (Centers for Disease Control and Prevention 2009).
The NHIS asks the respondent about insurance status and coverage type at the time of the survey. This survey also asks if the respondent has been uninsured for at least part of the year prior to the interview, and if the respondent has been uninsured for more than a year at the time of the interview. The question includes a comprehensive roll of insurance options that include public program names specific to the state in which the interview is conducted, as well as open-ended response options. A verification question is included to confirm that respondents who did not respond that they were enrolled in any insurance programs are, in fact, uninsured.