I found “BIRTHYR” variable in USA ipumps, but could not find it in 1980 USA samples in international ipumps. How can I find it?
BIRTHYR is IPUMS-USA is only available in 1% samples for 1900 and 1910. For other USA samples, BIRTHYR is a derived variable. In contrast, for IPUMS-International samples, BIRTHYR is a respondent reported variable. Therefore BIRTHYR in IPUMS-USA is not comparable with BIRTHYR in IPUMS-International.
To obtain the equivalent for IPUMS-USA 1980, subtract AGE from 1980–which is what is avialable from IPUMS-USA 1980.
Please see the IPUMS-USA BIRTHYR comparability discussion:
“Self-reported birth year is available only for the 1 percent samples for 1900 and 1910, in which it occasionally conflicts with self-reported AGE. IPUMS retains this original detail; users should exercise caution in these situations.”
Compare with the comparability discussion for IPUMS-International:
"There are no comparability issues across samples, apart from differing bottom-codes (see the codes page), the universe difference for South Africa 2007, and the use of the Hijiri calendar instead of the Gregorian one in the Iran and Morocco samples. "