When the IPUMS-created identifier CPSIDP is used to match individuals in adjasent years of the ASEC, do those individuals still match after they have been replaced by the swap values in the years that those exist?
Do you know if this match implies that the same individual’s records have been swapped in in both years, i.e. that the original matched individuals are replaced by swap values from individuals that also match accross these years?
If you don’t know, do you have any idea who at Census would be a good person to ask?
Since CPSIDP is simply an id that notes when an individual entered the sample, even if an individual’s income has been swapped in both, they will still have matching CPSIDP values. Said differently, CPSIDP is completely independent of income values. Swapping across both surveys only has to do with the income reported in that particular year. The Census does not go to an individual’s previous response to check whether they swapped that person’s value. That said, you can (and probably should) perform match validation exercises to ensure that no incorrect matches persist.