How is a record uniquely identified?
Three variables constitute a unique identifier for each person record in IHIS: YEARP, SERIALP, and PERNUM (survey year, household identifier, and person number within the household). The combination of YEAR and SERIAL (which have the same values as YEARP and SERIALP on the person record) constitute the unique household identifier on the household record. These are IHIS constructed variables and will not be found in the NHIS public use files. Individual households and persons can also be uniquely identified in a manner consistent with the NHIS public use files. The combination of YEAR and NHISHID will uniquely identify households, while the combination of YEAR and NHISPID will uniquely identify persons. NHISHID and NHISPID are constructed from data elements in the original NHIS public use files to produce the unique identifiers as defined by NHIS. These unique identifiers can be used as linking keys to merge variables from the NHIS public use files to IHIS data. More information about l
