STATEFIP and CPSIDP across months

#1

Is it right that the construction of CPSIDP does not allow values for STATEFIP to vary across months for the same individual?

This question comes from the following exercise. For unique individuals, identified with the individual’s CPSIDP, I am looking at the the values for STATEFIP across months that are a year apart (e.g. December 2011 vs. December 2012). For each individual present in the samples from both months, with nonmissing STATEFIP values in both months, I am finding STATEFIP values to be the same across months. I thought the values might be different over time for at least some individuals, indicating inter-state migration. But I am finding values of STATEFIP to be the same across months for each and every individual, indicating no inter-state migration.

#2

Yes, that would be correct.

Since the CPS does not follow households when they move from their current address, by construction, if the same invidual is present in multiple instances of the CPS, then he/she should have the same STATE of residence value. Otherwise it would be a coding error.