I’m currently using IPUMS data for some analysis, accounting for stratification and clustering in the samples to correctly estimate standard errors. I notice that the variable CLUSTER is “an integrated variable which uniquely identifies each household record in a given sample” (https://usa.ipums.org/usa/complex_sur…) and in turn is recommended for analysis. However, my understanding is that SERIAL also uniquely identifies each household in the sample. Are these variables functionally equivalent, or do they differ? Thanks for your guidance on this.