Based on what I’ve read on IPUMS tech documetation and this forum, I understand that when a user selects an IPUMS CPS sample, IPUMS CPS automatically generates a unique ID for each household, SERIAL. So, for example, if I select a 5-year March CPS sample with variables that draw from both the basic and the ASEC questionnaire, then all households within this sample will have a unique IPUMS-generated SERIAL number.The SERIAL variable disregards the rotating nature of the CPS in the sense that it does not have the same value for a household showing up in two consecutive March surveys (which happens about half of the time I believe). So, if this is correct, then all households within this 5-year sample will have unique SERIAL numbers, and it will not be possible to tell if two household records are actually the same household in two different years.
Question 1: Is the above is true? If so, why does IPUMS CPS also suggest using both YEAR and SERIALto uniquely identify households?
Question 2: If I download 10 variables for a 5-year March CPS sample, and then realize that I actually need another 2 variables, will the SERIAL values match between the original download (of 10 vars) and the additional download (of 2 variables)? In other words, within a given sample, are the SERIAL values generated are constant for each download? I understand that if I only wanted the additional two variables for 3 years of March data, this I would not be able to merge into my original 5 year dataset because SERIAL numbers are not comparable across samples.
Thanks for any insights