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. When a variable was modified globally, as part of the editing process, the third letter in the variable name was changed from a Q (i.e. INQ) to a D (i.e. IND). For example, some data were collected using two variables (a number variable and a unit of measure variable), but combined into a single variable for data release purposes.
IND235 (Family monthly income)
The respondent was asked to report total family income, received last month in dollars, for themselves and the other members of their family. Family monthly income is released as a range of values, in dollars, to minimize disclosure risks. The response categories are: $0 - $399, $400 - $799, $800 - $1249, $1250 - $1649, $1650 - $2099, $2100 - $2899, $2900 - $3749, $3750 - $4599, $4600 - $5399, $5400 - $6249, $6250 - $8399, $8400 and over. These response categories were chosen to mirror the categories used for reporting annual income.
INDFMMPI (Family monthly poverty level index)
This variable is an index for the ratio of 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 2006 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 2006 HHS poverty guidelines. For these respondents, answers to INQ238 and INQ241 were used to derive variable INDFMMPC.
INQ244, IND247 (Total savings/cash assets)
Total savings/cash assets questions for the family were only asked if the family’s annual income was equal or less than 200 percent of the 2006 HHS poverty guidelines. The respodent was first asked whether the family has savings or cash assets more than $5,000 (INQ244). If the family did not have savings or cash assets more than $5,000, the repondent would then be asked a follow-up question (IND247) to select a dollar range from a list printed on a hand card for the family’s total savings and cash assets amount.
The income questions were asked as part of household interview, 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 sample weights should be used.
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.