Why are IPUMS International data available at a lower admin unit as IPUMS Terra data for the same countries/years?

In some instances, for the same countries/years, data is available at a lower administrative unit (i.e., 2nd level) in IPUMS International than in IPUMS Terra (i.e., 1st level). To my knowledge, IPUMS Terra aggregates microdata from IPUMS International. So, I am confused as to why there is this discrepancy in the level of administrative units for the data. This presents an issue for me as I intend on using IPUMS Terra to extract aggregate population/household measures at the lowest administrative unit available in IPUMS International. Are these aggregate, lower administrative level data available elsewhere in the IPUMS ecosystem or should I proceed with aggregating IPUMS International microdata instead? Thank you in advance for your responses.

IPUMS Terra does utilize IPUMS International data, however Terra does not draw directly from the International database (yet). After International releases data, Terra must ingest the data into its own system. Terra also has stricter requirements for linkages between data and geographic boundaries than International does. Sometimes the Terra ingest process catches boundary-data issues that were not problematic for International. These issues must be addressed before Terra can complete the ingest process. We are currently in the final stages of fixing those issues and completing the ingest of the most recent International data release. Terra should soon be “caught up” with International and offering the same set of administrative levels that are currently available in International.

Thank you for your patience!