ACS Data Users Group

Hello,

I'm merging census block group data in 2010 decennial census with 2019 ACS. I find that the block group 060371370001 in 2019 ACS corresponds to 060379304011 in the 2010 decennial census. And block group 060371370002 in 2019 ACS corresponds to 060378002043 in the 2010 decennial census. And there is a slight boundary change in the border that divides these two blocks. I was wondering what leads to this inconsistency in block group ids in these two products, and what should I do with this if I want to merge census block group data in 2010 decennial census with 2019 ACS.

Thank you.

This is one of a handful of cases where tract and block group definitions were adjusted in 2011 and 2012. In this case, see the ACS 2012 Geography Changes:

Los Angeles County, California

The deletion of Census 2000 Tract 1370.00 is now corrected, and the tract is reinstated with its former boundaries. This change incorporates all of former (2010) Census Tract 9304.01 and part of (2010) Census Tract 8002.04 into the reinstated (2012) tract 1370.00.

For additional details on these tract and related changes, please see 2010 Census Geography Notes [PDF - <1.0 MB].

The Geography Notes doc lists the exact blocks involved in the definition change. If the 2010 data you need are reported at the block level, you could generate 2010 data for the 2019 block groups by aggregating data from the corresponding 2010 blocks.

Thank you so much. That helps a lot.