There appears to have been a change in EMPSTAT (A-LFSR in CPS) implementation in 2001.
From 2000 to 2001 (for age >= 18), the percentage of “NILF, retired” increased by ~3.3%, while “At work” and “NILF, other” decreased by 2.6% and 0.9%.
Note that this change is not specific to IPUMS - it can be seen in the underlying CPS file.
Does anyone know anything about this? I haven’t found anything from the CPS that describes a change in how ‘retired’ is determined.