BIRTHYR is a 4-digit-numeric variable.
9998: Not in Universe or Not Ascertained
9999: Unknown-Don't know
BIRTHYR is bottom coded to 84 years before the survey year (e.g. for 1997, bottom code is 1913: birth year 1913 and before; for 1998, bottom code is 1914: birth year 1914 and before).
For all persons, BIRTHYR reports the person's year of birth.
Beginning in 2017, NHIS has suppressed birth year; this variable is no longer available on public use files.
- 1997-2016: All persons.
- 1997-2016 : PERWEIGHT