The NHANES program suspended field operations in March 2020 due to the coronavirus disease 2019 (COVID-19) pandemic. As a result, data collection for the NHANES 2019-2020 cycle was not completed and the collected data are not nationally representative. Therefore, data collected from 2019 to March 2020 were combined with data from the NHANES 2017-2018 cycle to form a nationally representative sample of NHANES 2017-March 2020 pre-pandemic data. These data are available to the public. Please refer to the Analytic Notes section for more details on the use of the data.
The income section (variable name prefix INQ) provides family level information on monthly income. Information on family’s annual income was also collected in this section and was released as part of the Demographics file (P_DEMO).
All participants in the NHANES 2017-March 2020 pre-pandemic sample were eligible.
These questions were asked as part of the NHANES Family Questionnaire, in the home, using the Computer-Assisted Personal Interview (CAPI) system. Hand cards showing response categories were also used for some questions. One respondent in each family answered these questions.
The NHANES 2017-2018 and 2019-2020 income questionnaires are available on the NHANES website.
The CAPI system is programmed with built-in consistency checks to reduce data entry errors. CAPI also uses online help screens to assist interviewers in defining key terms used in the questionnaire. All of the data was reviewed by the NHANES field office staff for accuracy and completeness.
Frequency counts were checked, “skip” patterns were verified, and the reasonableness of question responses was reviewed. Edits were made to some variables to ensure the completeness, consistency, and analytic usefulness of the data. Edits were also made, when necessary, to address data disclosure concerns.
INDFMMPI (Family monthly poverty level index)
The respondent was asked to report total family income, received last month in dollars, for themselves and the other members of their family. This variable is an index for the ratio of reported monthly income to poverty. The Department of Health and Human Services’ (HHS) poverty guidelines were used as the poverty measure to calculate this index. These guidelines are issued each year, in the Federal Register, for determining financial eligibility for certain federal programs, such as Head Start, Supplemental Nutrition Assistance Program (SNAP) (formerly Food Stamp Program), Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), and the National School Lunch Program. The variable INDFMMPI was calculated by dividing family income by the poverty guidelines, specific to family size, as well as the appropriate year and state. Values at or above 5.00 were coded as 5.00 or more because of disclosure concerns. The values were not computed if the family income data was missing.
INDFMMPC (Family monthly poverty level index category)
For respondents who reported their family monthly income in dollar amounts, we calculated their family monthly poverty level index (INDFMMPI) as described above. The index was then grouped into three categories (i.e., INDFMMPI ≤ 1.30, 1.30 < INDFMMPI ≤ 1.85, INDFMMPI >1.85) and reported in this variable. These categories were chosen because they represented commonly used percentages of the poverty guidelines (i.e., 130 percent and 185 percent of the guidelines), by federal programs, in determining eligibility.
When the respondent refused to answer the family monthly income question or did not know the total combined family income, a monthly income screener question was asked (question INQ238) to query whether the monthly family income was below 185% of the HHS poverty guidelines. If the response was positive, a follow-up question (INQ241) was asked to see whether the family’s monthly income was more or less than 130% of the HHS poverty guidelines. For these respondents, answers to INQ238 and INQ241 were used to derive variable INDFMMPC.
The COVID-19 pandemic required suspension of NHANES 2019-2020 field operations in March 2020 after data were collected in 18 of the 30 survey locations in the 2019-2020 sample. Data collection was cancelled for the remaining 12 locations. Because the collected data from 18 locations were not nationally representative, these data were combined with data from the previous cycle (2017-2018) to create a 2017-March 2020 pre-pandemic data file. A special weighting process was applied to the 2017-March 2020 pre-pandemic data file. The resulting sample weights in the present file should be used to calculate estimates from the combined cycles. These sample weights are not appropriate for independent analyses of the 2019-2020 data and will not yield nationally representative results for either the 2017-2018 data alone or the 2019-March 2020 data alone. Please refer to the NHANES website for additional information for the NHANES 2017-March 2020 pre-pandemic data, and for the previous 2017-2018 public use data file with specific weights for that 2-year cycle.
The income questions were asked as part of household interview, therefore, the interview sample weights may be used in the analysis for data in this section. However, if the data is joined with other data from the Mobile Examination Center (MEC), the MEC exam weights should be used for analyses.
Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues. Both of these are available on the NHANES website.
Disclosure risks and issues pertaining to confidentiality protection prevent NCHS from releasing all of the NHANES demographic or income variables publicly. Additional information and instructions for requesting use of these data are available through the NCHS RDC.
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0 to 4.99 | Range of Values | 10827 | 10827 | |
| 5 | Value greater than or equal to 5.00 | 1497 | 12324 | |
| . | Missing | 3236 | 15560 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 1 | Monthly poverty level index =1.30 | 5142 | 5142 | |
| 2 | 1.30 < Monthly poverty level index = 1.85 | 2028 | 7170 | |
| 3 | Monthly poverty level index >1.85 | 6495 | 13665 | |
| 7 | Refused | 111 | 13776 | |
| 9 | Don't know | 482 | 14258 | |
| . | Missing | 1302 | 15560 |