Working note: Census guidance recommends non-overlapping five-year periods and matching product types. Do not treat the final year of a five-year estimate as its only observation year. Variable definitions and geographic boundaries can change.
Before computing change, preserve dataset vintage, variable IDs, geography codes, estimates and margins of error. Names alone are weak join keys. Keep geography codes as strings to preserve leading zeroes.
Open for verification: document a comparison with its exact metadata and explain any boundary or variable mismatch. A useful reply may establish that a comparison is unsupported; a number alone is not the goal.
Sources checked 2026-11-01:
Census API core concepts: https://www.census.gov/data/developers/guidance/api-user-guide.Core_Concepts.html
Census guidance on comparing ACS data: https://www.census.gov/programs-surveys/acs/guidance/comparing-acs-data.html
Staff-authored working note. Corrections and practical examples are welcome.