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NHIS unique identifier for previous year, person


NHISPIDPRVYR is a 16-character string variable.

-999999999999998: NIU


NHISPIDPRVYR is an IPUMS NHIS-constructed variable available for sample adults in the 2020 longitudinal sample that contains the unique identifier for a person from the previous survey year. Users may link an individual in the 2020 longitudinal sample to their record in the 2019 file by linking on the person's 2020 value of NHISPIDPRVYR and the person's 2019 value of NHISPID. For example, for a sample adult in the 2020 longitudinal file, renaming NHISPIDPRVYR to NHISPID allows a user to perform a one-to-one merge between the sample adult's 2019 record and their 2020 record.

Due to the coronavirus pandemic in 2020, about half of the original NHIS sample allocated for the last five months of 2020 was replaced with persons that had completed a Sample Adult interview in the 2019 NHIS. This group of sample adults that completed interviews in the 2019 and 2020 NHIS are referred to as the "longitudinal" sample. No sample children were included in the longitudinal sample due to methodological concerns. Persons in the longitudinal sample were interviewed for the 2020 NHIS at least 12 months after their initial 2019 interview. According to the 2020 Survey Description, the longitudinal sample was introduced "due to concerns about possible loss of coverage and lower response rates typically associated with telephone interviewing" and to provide "an opportunity to assess changes over time in health outcomes measured in both survey years and assess measures during the pandemic." Please see the user note on COVID-related changes to the NHIS for more information.

LONGWEIGHT should be used in analyses evaluating individual-level changes between 2019 and 2020 among the same adults.


This variable is comparable over time.


  • 2020: Sample adults age 18+ included in the longitudinal sample.


  • 2020