ACS Data Users Group

I'm wondering if anyone can nudge me in the right direction. I'm trying to divvy up ACS congressional district data (116th session) into 118th session districts (since 118th isn't available yet). Is there something like a crosswalk file that accomplishes this already? I've done some searching but haven't come across one yet and am hoping I'm just overlooking it. I've currently created a union of the spatial files of the two sessions, but still need to apportion some 116th district polygons because they overlap 118th boundaries.

One option is to access the 116 and 118 block equivalency files (available here and here), and access a 2010-2020 block crosswalk from IPUMS NHGIS (available here) -> you could re-apportion the data by going down to the block level and using block-level population weights before re-summing. Another easier option that uses a similar method (if you code in R) would be to use the interpolate_pw() function from tidycensus() that allows you to use 116 and 118 spatial files, plus a third spatial file containing blocks (you'd need to choose 2010 or 2020) and a population weight of interest.

We have some ACS data available for the 118th Congress on the Congressional District Health Dashboard. We use a third method that you might also consider, which is going from tracts->118th Congress using a similar block population weighting method. Feel free to email us if you'd like to discuss further.

I do code in R and will definitely try this!!

You could use Geocorr:

https://mcdc.missouri.edu/applications/geocorr2022.html

That's great - I didn't realize that Geocorr could go across DCS geographies! Very useful.

Here's a Geocorr query that will get you a crosswalk between 118th and 116th CDs for all states:

mcdc.missouri.edu/.../broker

I agree Geocorr is a great resource for this, but I'd strongly recommend against a simple 116th to 118th crosswalk if you can avoid that. Instead, I'd crosswalk from smaller units to 118th CDs... blocks, block groups, tracts, county subdivisions... whatever the smallest areas are for which you can get the data you need. Any of these areas nest much better within 118th boundaries, and therefore allow you to aggregate up confidently, rather than disaggregate from 116th areas--resulting in needless estimation error--anywhere they're split by 118th boundaries.

We discuss this general principle on the IPUMS NHGIS crosswalks page here, but NHGIS crosswalks don't directly support bridging to 118th CDs. The Geocorr relationship files do.

Then again, if the data you're working with are available *only* for 116th CDs, then yes, a direct crosswalk is reasonable. You could still try some more advanced allocation approaches, but weighting by the population counts that Geocorr provides should work well enough in most cases.

Good points Jonathan Schroeder -- I was mostly going to the crosswalk question

Thank you for sharing this! I didn't realize it existed and will definitely add to my bookmarks.

FYI--The Census Bureau released 2021 ACS 1-year Data Profiles for the 118th Congressional Districts at www.census.gov/.../.

I did see these, but I'm in a bit of a time crunch and the reformatting/recoding to use them requires more time that I have at the moment. I should've said it's not available in the format I need, and that's why I asked for something like a crosswalk solution for the time being.