I downloaded IPUMS CPS 70s and 80s samples. I selected Earner Studies variables (Outgoing Rotation Group). Those variables are not available for 1979 to 1981 IPUMS CPS samples while the NBER provides MORG files for those years (http://www.nber.org/morg/sources/arch…). Furthermore, some academic studies such as Balleer and Rens (2013) use the earner study variables starting from 1979.
Thus, are those variables absent from 1979 to 1981 IPUMS CPS samples due to inconsistencies in the raw data or work in progress or else?