MORTWT is a variable with eight columns and no implied decimal places.
For persons aged 18 and older included in the 1986 to 2014 NHIS samples, MORTWT reports the sampling weight that adjusts for ineligible respondents in analyses of data linking NHIS participants during survey years 1986 to 2014 to the National Death Index (NDI) with mortality follow up through December 31, 2019. Because of changes in the universe of NHIS participants linked to the NDI, that is, included in the Linked Mortality File (LMF) data, mortality analyses including participants in the 2015 and later NHIS samples should instead use MORTWTSA.
Because adult survey participants who provided insufficient data for linking may differ from those who provided enough data for linking, ignoring the ineligible adult respondents could lead to biased mortality analysis. To correct this bias, the National Center for Health Statistics (NCHS) developed the eligibility-adjusted weights for use with variables in the 2019 LMF update: MORTWT and MORTWTSA.
NCHS cautions that the MORTWT, rather than the standard person weight (PERWEIGHT), should be used when analyzing mortality variables in conjunction with variables from the person files for all years other than 1986. Similarly, MORTWTSA should be used when analyzing mortality variables in conjunction with variables from the sample adult files. In 1986, NCHS did not produce an eligibility-adjusted weight for use with the mortality data and instead recommends that analysts use values for PERWEIGHT; the IPUMS variable MORTWT in 1986 reports values of PERWEIGHT for persons eligible for mortality follow-up (MORTELIG values of 1). In the 2015 and later samples, only sample adults are eligible for linkage to the NDI and all analyses of the mortality data from the 2015 and later samples should employ MORTWTSA.
MORTWT is one of a set of mortality variables released by NCHS as part of the 2019 LMF update. The 2019 LMF includes mortality information for participants in the 1986-2018 NHIS samples with mortality follow up in the NDI through December 31, 2019. For more information on the LMF, including which variables it offers and the appropriate sampling weights to use when analyzing the mortality data, see the description tab of MORTELIG.
For a list of all mortality variables from the LMF included in the IPUMS NHIS, please refer to the MORTELIG variable description.
With the exceptions of 1986 and 1992, MORTWT is completely comparable over time. In 1986, the NCHS did not adjust the original NHIS person weight to control for selection bias, so in analyses using the 1986 mortality data, MORTWT reports the same value as PERWEIGHT for persons eligible for mortality follow up. In 1992, MORTWT values include the Hispanic oversample. For more information about how the Hispanic oversample may affect analyses that pool 1991 and 1992, please refer to this IPUMS NHIS user note.
For an overview of the LMF data, NHIS-NDI linkage activities, and more information about the public-use LMF offered through IPUMS NHIS, please refer to our user note on the Linked Mortality File.
- 1986-2014: All persons age 18+ eligible for mortality follow-up (MORTELIG).