ACS Data Users Group

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  • 1.  Missing Block Groups

    Posted 02-09-2022 03:31 PM

    I'm comparing block groups in two publications: TIGER/Line shape files and their ACS 2019 estimates. I'm finding as much as a third difference in the block group keys between the two. Looking just at Florida (FIPS 12) as an example:

    Their block group IDs differ this way:

    • TIGER/Line file has 13,388 block groups in the state. ACS has 11,442 block groups.
    • TIGER shapefiles have 5,255 block groups NOT available in the ACS set. For example:

    '121030255091', '120210003014', '120190312022', '120090651272', '120110703291', '120990019073'

    • ACS has 3,309 block groups NOT available in the TIGER shapefiles

    '120570116071', '120690313112', '120860096001', '121113820034', '120860058025', '121050124032'

    I understand some block groups may be suppressed in the estimates, and of course there are incremental changes in block group definitions over time. But, these do not explain the size of the difference here. Can you help me reconcile these?

    Thanks in advance!

    Michael



  • 2.  RE: Missing Block Groups

    Posted 02-09-2022 04:11 PM

    the 2021 block groups will be different from the ones used in ACS 2019, which are the 2010 block groups.



  • 3.  RE: Missing Block Groups

    Posted 02-09-2022 04:12 PM

    Also, BG definitions are not incremental. They change every 10 years.



  • 4.  RE: Missing Block Groups

    Posted 02-09-2022 04:42 PM

    What Glenn said. The 2019 will be for 2010 geography and the 2021 will be for 2020 geography. The annual changes released each year as "vintages" are usually small geometry corrections.



  • 5.  RE: Missing Block Groups

    Posted 02-10-2022 10:12 AM

    THANKS

    brilliant

    you've cleared a major impediment to my work