Add Notes About How Census Boundaries Change Over Time

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For example, core boundaries of core types like tracts can change with every decennial census (e.g., if population grows too large, a tract may be split into multiple tracts). Other boundaries may change more frequently.

Important to note because this means that you have to ensure that any data pulled from the census matches the boundary dataset used (e.g., you can't associate tract-level census data from the 2022 ACS with pre-2020 tract boundaries; the data will be describing different boundaries). It also means that you can't always directly compare data for the same census unit across years (e.g., a tract's boundaries may have changed between the 2019 ACS and the 2022 ACS, so you can't directly compare data for that tract across those years).