Family income

Respondents to the National Health Interview Survey and the National Health and Nutrition Examination Survey are classified according to the total income of the family. Broadly, a family is defined as people living together who are related by birth, marriage, or adoption. The surveys differ in how they handle unrelated household members, unrelated children, and unmarried partners living together. Respondents are asked about possible sources of income for their family members, including wages, salaries, interest and dividends, federal programs, child support, rents, royalties, and other possible sources. Unrelated household members are classified according to their own income. More information about how the surveys define families and collect income data follows.

National Health and Nutrition Examination Survey (NHANES)

In the continuous NHANES, 1999 and onward, respondents are asked about possible sources of income for their family members and combined family income (in dollars) from all sources before taxes for the calendar year before the interview. If respondents do not know or refuse to give a dollar amount in response to this question, they are asked if the total family income was less than $20,000 or $20,000 or more. A follow-up question asks them to select an income range from a list on a printed flash card (a range of less than $1,000 to $19,999 if reported family income is less than $20,000, and a range of $20,000 to $100,000 and over if reported family income is $20,000 or more). The midpoint of the income range is used as the total family income value.

NHANES III (1988–1994) asked respondents to identify their income based on a set of ranges provided on a flash card but did not ask detailed sources-of-income questions. Family income has not been imputed for individuals or families with no reported income information in any of the NHANES survey years. Family income values are used to calculate percentage of federal poverty level. (Also see Sources and Definitions, Poverty.) For the most recent information on the NHANES family income questions, see: NHANES 2019–2020 family questionnaire: Income.

NHANES defines a family as a group of two or more people living together who are related by birth, marriage, or adoption. A family includes unmarried partners if they have a biological or adoptive child in common; however, it does not include unmarried partners who do not have a child in common, foster parents, or foster children.

National Health Interview Survey (NHIS)

Since 1997, NHIS asks respondents about family income from the calendar year before the interview (for example, a respondent interviewed in 2021 is asked about income for 2020). Before 1997, family income was the total income received by members of a family in the 12 months before the interview. Respondents are asked about possible sources of income for their family members and asked to report their “best estimate” of their family’s total income (in dollars) from all sources for all family members living in the household before taxes. Beginning with the 2007 NHIS, if respondents do not know or refuse to provide an answer in response to the exact-income amount question, they are asked a series of closed-ended income range questions (for example, “Is it less than $75,000, or $75,000 or more?”). The closed-ended income range questions are constructed so that each successive question establishes a smaller range for the family’s income. These questions were further refined starting with NHIS 2011. In the 1997–2006 NHIS, respondents who did not know or refused to provide an answer in response to the exact-income amount question were asked if their total family income for the previous year was $20,000 or more, or less than $20,000. A follow-up question asked them to select an income range from a list on a printed flash card to indicate the income group that best represented their family’s income during the previous calendar year.

NHIS defines a family as an individual or a group of two or more people living together who are related by birth, marriage, or adoption. A family includes any unrelated children who are cared for by the family (such as foster children) and any unmarried cohabiting partners and their children. Unmarried couples are considered as belonging to the same family.

For the most recent information on the family income questions in NHIS, see: “Characteristics About the Family and Household of the Sample Adult and Sample Child in “National Health Interview Survey: 2019 Survey Description” and “Impact of Income Bracketing on Poverty Measures Used in the National Health Interview Survey’s Early Release Program: Preliminary Data From the 2007 NHIS.”

Family income data are used to calculate the percentage of federal poverty level. For data years 1997–2021, about 20%–34% of people had missing data on family income (FamIncome-Table). Multiple imputation was performed to impute missing data on family income for NHIS survey years 1997 and beyond. Imputed income values have been used in Health, United States trend tables starting with Health, United States, 2004. Five sets of imputed values were created for the 1997–2018 NHIS to assess the variability caused by imputation. Starting with the 2019 NHIS, 10 sets of imputed values are created to assess the variability more precisely. A detailed description of the multiple-imputation procedure and data files, with imputed family income for 1997 and beyond, is available from NHIS Data, Questionnaires and Related Documentation through the Data Release page for each survey year.

For data years 1990–1996, about 16%–18% of people had missing data on family income (FamIncome-Table). In those years, missing values were imputed for family income using a sequential hot-deck imputation approach, imputing missing values from another record with similar characteristics. A detailed description of the imputation procedure and data files, with imputed annual family income for 1990–1996, is available from the NHIS 1990–1996 Family Income data set. (Also see Sources and Definitions, Poverty.)

National Immunization Surveys (NIS) (last updated June 2023)

Before 1998, family income was the total income received by all family members in the 12 months before the interview. Starting in 1998, NIS collects family income data for the calendar year before the interview year for households with age-eligible children. Family income is the combined total income (in dollars) received by all members of a family before taxes in the last calendar year. Respondents who do not know or refuse to give a dollar amount for the total family income are asked a cascading sequence of income questions—a total of 15 questions—that attempt to place the family income into 1 of 15 income intervals ranging from $7,500 or less to $75,000 or more. The initial question asks if the family income for the previous calendar year was more or less than $20,000. Subsequent sets of income range questions are asked so that each successive question establishes a narrower income range.

A family income variable is constructed from the total family income question and the cascading income questions. If an exact income is given, family income is set to this amount; otherwise, it is set to the midpoint of the tightest bounds established by the cascading income questions. The values of total family income are used to calculate an income-to-poverty ratio. For NIS, this ratio is calculated only for households with age-eligible children, using either the actual family income value or the midpoint of the interval from the series of cascading questions in the numerator and the U.S. Census Bureau’s poverty threshold for family size and number of related children in the household in the denominator. Details of the income questions and computation of the income-to-poverty ratio for each data collection year can be found in the NIS data documentation (“Data User’s Guide” and “Household Interview Questionnaire” for NIS–Child and NIS–Teen).

For more information, see: “Improving Income Imputation by Using Partial Income Information and Ecological Variables.”

FamIncome-Table. Imputed family income percentages in National Health Interview Survey, by age (years) and sex: United States, 1990–2022

NOTE: Data shown are weighted percentages.

SOURCE: National Center for Health Statistics, National Health Interview Survey. See Sources and Definitions, National Health Interview Survey (NHIS).