Are there archives of old versions of the database I can access? For instance, I might want to get data as they were coded in January 2010.
I see that this has been asked at least five times before, but none of the responses to those posts actually answered the question.
Yes, we do keep archived versions of the IPUMS databases. There is a new snapshot taken about once per year. You can find the dates a particular snapshot was taken by visiting ipums.org and choosing a project from the “Projects” drop-down menu (click on a particular version and look at the last paragraph of the version’s page). That said, we encourage data users to use the current version of the database, and use the revision history page (here is the one for IPUMS CPS) to identify differences between the current version and previous versions. We only share an archived version if there is a legitimate research need for which the revisions history does not contain enough information. Please email firstname.lastname@example.org if you have a need for an archived version.
Is there any chance of accessing CPS microdata from before the 1990s in the original form IPUMS received them from the Census? I need to replicate an old paper that used Unicon files, but applying the author’s sample selection rules to IPUMS files does not recover the same sample size.
Can you give more details about the mismatch? We should be able to figure this out without sharing source files. It may be easier to switch to email. Please send a message to email@example.com.
One thing to note is that households without interviews in the original data do not have person records in IPUMS data. You may want to make a hierarchical extract to compare the number of households including non-interviews. You can select this as an option when submitting your extract. Hierarchical extracts have one record for each household, followed by person records for each household members.