NHISHID is a 14-character string variable.
NHISHID is an IPUMS NHIS-constructed value that is an identifying number unique to each household in a given survey year. Using NHISHID, analysts can link IPUMS NHIS data with additional household-level data elements, from the NHIS source public use data files, that are not currently available in IPUMS. NHISHID is a single variable constructed by concatenating multiple data elements from the NHIS source data files. Analysts wishing to link person-level NHIS data should use the person-level linking key NHISPID.
See the user note on LINKING for instructions on how to create links between IPUMS NHIS and NHIS source data.
The variables concatenated to construct NHISHID differ by periods. There are four discrete periods, namely: 1) 1968-1991 and 1993-1994; 2) 1992; 3) 1995-1996; and 4) 1997-forward. While the particular combination of variables used to construct NHISHID differs between these periods, the substantive meaning of the variable is consistent across years. In the discussion that follows, the elements of NHISHID are identified via the variable names used in the original NHIS public use data source files.
The sequential elements in NHISHID before 1994 (except for 1992) are processing quarter (QUARTER), PSU number (PSUNUMR), census week (WEEKCEN), segment number (SEGNUM), and household number (HHNUM).
The sequential elements of NHISHID for 1992 are processing year (YEAR), processing quarter (QUARTER), PSU number (PSUNUMR), census week (WEEKCEN), segment number (SEGNUM), and household number (HHNUM).
The only element of NHISHID for 1995 and 1996 is household ID (HHID).
For 1997 forward, the sequential elements of NHISHID are processing year (YEAR) and household serial number (HHX).
- 1963-2018: All households (NHIS samples).
- 1963, 1966-1967, 1969-2018 : HHWEIGHT