I am checking to see if there are differences in PWPUMAs starting in 2022, since these are now based on the 2020 PWPUMAs. Looking at Los Angeles specifically, the map on the PWPUMA00 documentation page appears to show that PWPUMA 3700 is the same for 2010 and 2020. However, when looking at the crosswalk, it lists multiple 2020 codes as corresponding to the 2010 3700 code. Is this an error in the crosswalk? Here is a screenshot of the crosswalk filtered to California and PWPUMA10 3700.
The crosswalk is consistent with the Census Bureau’s official delineations of 2010 and 2020 boundaries, which means that the 2010 and 2020 versions of PWPUMA 03700 are not a perfect match. But they’re extremely close to being a perfect match.
Both the 2010 and 2020 version of this PWPUMA correspond exactly to the Census Bureau’s delineation of Los Angeles County, but the Bureau occasionally makes improvements to its spatial boundary data for reporting areas, including states & counties. These improvements do occasionally impact where some residences are counted in census data, such that a particular residence may occur on one side of a 2010 boundary representation and on the other side of a 2020 boundary representation, thus “moving” in or out of a county in the census data even without any physical or legal change.
But in this case, we expect that the affected residences involve only a very small population (if any). As you can see in the “Part_Pop10” column in the screenshot, nearly all of the 2010 population of the 2010 PWPUMA 03700 lives in a part corresponding to the 2020 PWPUMA 03700. These numbers, which are estimates based on IPUMS NHGIS geographic crosswalks, indicate that only about 15 people out of 9.8 million lived in an area that became part of a different 2020 PWPUMA. Fortunately, I expect there are few research applications where it would be important to take account of this 0.00015% discrepancy, so I’d suggest you could safely ignore it.
Farther to the right in the PWPUMA crosswalk, you can also find a “Part_Land” column, which reports the area of each intersection between a 2010 and 2020 PWPUMA in square meters. You’ll see that the areas involved in the boundary changes between the 2010 & 2020 versions of PWPUMA 3700 are also very small (several thousand square meters each), which could make them difficult to find in the web map.
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