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