I’m using the BG2020 to BG2010 crosswalk on an extract from 2023 ACS5 for the whole US. I see that most of the 2020 block groups in CT and some in NY do not match between the crosswalk and the table extract. Connecticut in particular has 09001, 09003, etc in the crosswalk, but I think the county boundaries were changed in 2020 and should be 09110, 09120, etc. Does the crosswalk predate that change, or am I misunderstanding something? Thanks in advance!
The Census Bureau began using new county equivalents in Connecticut in the 2022 ACS data, replacing the historical Connecticut counties with new planning regions. Each full block group ID is a concatenation of state, county, census tract, and block group codes. The 2020 block group IDs in NHGIS crosswalks use the older Connecticut county codes. The block group IDs in 2022 and later ACS data use the new county-equivalent codes.
We describe this issue in this section of the NHGIS crosswalks page. There we recommend “using Geocorr 2022 to obtain a relationship file between 2020 census units and the newly identified Connecticut planning regions.” With that, you could determine how the 2023 block group IDs correspond to the 2020 IDs in NHGIS crosswalks.
We are also working on extending our crosswalks to address these changes.
The mismatches in New York are a separate issue. As explained in the Census Bureau’s Errata Notes 147 and 148, the Bureau stopped publishing data for several block groups in New York due to geocoding and data collection errors. They plan to resume publishing data for those block groups in future releases.
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We have now extended our crosswalks to address changes that occur in non-census years, including the new Connecticut county equivalents. You can read more about the scope of this release in our news item about it, and you can download the files through the Geographic Crosswalks page.