Hello!
I would like to know if individuals can be traced between censuses. In other words, is individual 1 always the same in all censuses (of the same country)?
Most IPUMS data collections are cross-sectional and do not follow the same individuals over time. Variables like SERIAL and PERNUM are sample-specific and should not be used as linking keys. IPUMS does offer some survey data with a panel component (IPUMS CPS, IPUMS MEPS, IPUMS PMA) as well as linking keys for historical US census microdata via IPUMS USA.