WEIGHT is a 3-digit-numeric variable. The upper and lower weight thresholds for public data suppression vary over time. User should carefully review the codes below before making cross-year comparisons or interpreting results.
2019-forward codes
000: Not in Universe
100-299: 100-299 pounds
996: Exceptionally low or high weight or sex is missing
997: Unknown-refused
998: Unknown-not ascertained
999: Unknown-don't know
1997-2018 codes
000: Not in Universe
99: 99 pounds or less (FEMALES only, 1997-2005)
100: 100 pounds or less (FEMALES only, 2006-2018)
126: 126 pounds or less (MALES only, 1997-2018)
259: 259 pounds or more (FEMALES only, 1997-2005)
274: 274 pounds or more (FEMALES only, 2006-2018)
285: 285 pounds or more (MALES only, 1997-2005)
299: 299 pounds or more (MALES only, 2006-2018)
996: Exceptionally low or high weight
997: Unknown-refused
998: Unknown-not ascertained
999: Unknown-don't know
In 1997-2018, data are NOT top and bottom coded, but instead cases outside of these upper and lower bounds are assigned to a code of "996: Exceptionally low or high weight". Additionally, these thresholds differ by sex.
Pre-1997 codes:
000: Not in Universe (includes 2 reported "0" values in 1974, which has no bottom-code)
50: 50 pounds or less (1976-1995)
97: 97 pounds or less (1996)
290: 290 pounds or more (1996)
300: 300 pounds or more (1976 and 1978)
400: 400 pounds or more (1977, 1979-1981)
500: 500 pounds or more (1982-1995)
997: 997 pounds or more (1974)
995: Unknown - all causes
Description
WEIGHT reports the approximate weight of sample adults and sample children ages 10-17, in pounds. Prior to 2020, WEIGHT is only asked of adults. The values for this variable are based on self-reports or proxy reports/estimates by respondents for other household members, supplied in response to the question, "About how much does [person] weigh without shoes?" In 1974 only, the question does not specify "without shoes" and in 1976 and 1977 the question specifies "without clothes or shoes."
Such verbally reported data are less accurate than, and thus not fully comparable to, data on weight gleaned via direct measurement in other surveys, such as NHANES (the National Health and Nutrition Examination Survey fielded by the National Center for Health Statistics). Indeed, the Field Representative's Manual for 1991 specified that one rationale for collecting height and weight data in the NHIS was to compare respondents' answers to the distribution of actual body measurements obtained in the Health and Nutrition Examination Survey, "to determine the reliability of self-reported or proxy-reported heights and weights."
Comparability
Please review the universe tab for information on changes to the age and sub-sample status of persons included in the universe of this variable over time. Along with changes in the variable universe and major questionnaire changes introduced in 2019, changes in top- and bottom-codes limit the comparability of this variable over time.
In 1974, persons could report weighing between 0 and 997 pounds; outlier cases should be treated cautiously. For 1976, the recognized range was 50 to 300 pounds; for 1977-1981, 50 to 400 pounds; for 1982-1995, 50 to 500 pounds; for 1996, 97 to 290 pounds. In 1997-2018, the recognized range for weight differed between men and women. For 1997-2005, the range for men was 126 to 285 pounds; for women, 99 to 259 pounds. For 2006-2018, the range for men was 126 to 299 pounds; for women, 100 to 274 pounds. According to the 2006 Survey Description Document, the upper threshold for weight was raised for both men and women and the lower threshold was raised for women beginning in 2006 "due to the increasing numbers of overweight and obese adults." Beginning in 2020, weight is reported for sample children ages 10-17 with a recognized range of 50 to 280 pounds for boys and 46 to 230 pounds for girls.
The question for WEIGHT in 1977 was asked for a sub-sample of randomly selected persons age 20 and over; NHIS automatically classifies persons who were selected but did not complete the questions as responding "unknown-all causes" for this variable. Users may choose to use this variable in combination with SUBSRESP77, which reports the person's sub-sample status in 1977.
For years prior to 1997, persons who weighed more than the top-coded value or less than the bottom-coded value were included in the highest and lowest categories, respectively. Thus, for example, in 1996, category 290 includes people who weighed 290 pounds or more. By contrast, for 1997-2018, persons who whose weight was exceptionally low or high were grouped together in a separate "Exceptionally low or high weight" category (code 996). As the Survey Description Document for 1997 explained, "Beginning in 1997, when a very large or very small value was reported for either height or weight, the data in both variables were changed to '96' or '996' ('Not available') on the public use data files. This was done to protect the confidentiality of NHIS respondents who might be identifiable by their unusual physical characteristics."
Beginning in 2019, respondents whose sex was unknown also had their weight values coded as 996. The 2019 Codebook for Sample Adult File states that this change was made, "due to the sex-specific height and weight limits for public data release."
Because of changes in the recognized ranges and in the treatment of outlying values, analysts should exercise caution in comparing results across periods.
For example, average weight calculated using 1976 data would necessarily be less than average weight calculated using 1977 data, because the topcodes for the two years differ (300 pounds versus 400 pounds). For comparisons across periods, the best approach would be to limit the sample to persons whose weight falls within the smallest recognized range for the period under study and exclude persons assigned the top or bottom codes.
To achieve comparability across all years, researchers should restrict their analysis to persons whose weight fell within the smallest recognized range across all years, namely, from 100 to 285 pounds.
Questionnaire design changes introduced in 2019 limit comparability with earlier years. The NHIS questionnaire was substantially redesigned in 2019 to introduce a different data collection structure and new content. For more information on changes in terminology, universes, and data collection methods beginning in 2019, please see the user note.
Universe
- 1974: Sample persons age 17+.
- 1976: Persons age 17+.
- 1977: Subsampled persons age 20+.
- 1978-1981: Persons age 17+.
- 1982-1996: Persons age 18+.
- 1997-2018: Sample adults age 18+.
- 2019: Sample adults age 18+.
- 2020 2022: Sample children ages 10-17 and sample adults age 18+.
- 2021; 2023: Sample adults age 18+.
Availability
- 1974, 1976-2023
Weights
- 1976, 1978-1996 : PERWEIGHT
- 1974, 1997-2023 : SAMPWEIGHT
- 1977 : SUB77WT
