Hi Chuck—

Thanks for the heads-up.  Yes, that is the way to think of PUMAs = as “super-districts” or sub-state regions. 

Here are my “pro-tips” learned in PUMA drawing 10 years ago:

1. Do not group together fractional pieces of counties when you could keep a county whole, or when you could group multiple whole counties together in a PUMA.
2. When splitting counties into multiple PUMAs, try to arrange for the split lines to be stable city/town boundaries.  This means you’re looking to create PUMAs where city/town boundaries are aligned with Tract boundaries. (Because Census Geog Dept will require that tracts be the basic units of PUMA assembly.)

The reason I emphasize parsimony with counties in point #1 is: The PUMAs you draw will enable or limit the detail of MIGPUMAs as well. (MIGPUMA= Migration origination geographic units)  Census Bureau will create MIGPUMAs as the least common denominator grouping of counties that is entirely coincident with a group of PUMAs.  So don’t split counties unnecessarily.

The reason I emphasize city/town boundaries in point #2 -- even though Census Geog discusses tracts as the basic units – is this: The PUMAs you draw will enable or limit the detail of POWPUMAs. (POWPUMAs = Place of Work geographic units)  Census Bureau will create POWPUMAs as the least common denominator grouping of counties + places that is entirely coincident with a group of PUMAs.

Stated differently: Census looks for combinations of county + place to uniquely nest within a POWPUMA.

Why is this the standard for POWPUMAs? It’s because of the questions asked on ACS: ACS asks specifically for the county + place of one’s work location.  The PUMA final criteria document  https://www.census.gov/programs-surveys/geography/guidance/geo-areas/pumas/2020pumas.html  does say all this, but you’d have to read all the way to the last 3 pages of that document to find it.

That’s all my advice. Good luck!

--Todd Graham

Todd Graham Principal Forecaster  |  Research Metropolitan Council 390 North Roberrt Street, St. Paul, MN 55101 Ph. 651-602-1322  metrocouncil.org | facebook | twitter

From: Charles Purvis <clpurvis@att.net>
Sent: Monday, August 23, 2021 12:32 PM
To: ctpp@listserv.transportation.org
Subject: [CTPP News] Defining PUMAs for Census 2020

The Census Bureau is ramping up efforts for Census 2020 PUMA delineation. PUMAs are “Public Use Microdata Areas.” They are large, contiguous areas of 100,000+ population, built up from census tracts and counties.

Here’s the main Census Bureau page on PUMA 2020:

https://www.census.gov/programs-surveys/geography/guidance/geo-areas/pumas/2020pumas.html

The Census Bureau will be kicking off the program in September 2021 (next month!). This will be an announcement to each State Data Center points of contact.

If you’re an MPO, you might be part of your state’s State Data Center Network (as an affiliate data center, regional data center, etc.) Get in touch with your state’s SDC. It will be each SDC that provides proposed PUMAs to the Census Bureau.

The actual work on defining the new Census 2020 based PUMAs will be November 2021 through January 2022, with the “final” 2020 PUMAs published by summer 2022.

My key point: the PUMAs are NOT just for use in the Public Use Microdata Sample, but are used as STANDARD tabulations for the American Community Survey, both the 1-year and 5-year products. As such, the PUMAs can be thought of as “Regional Analysis Districts” or “Superdistricts” or “Regional Districts.” They can be SUPER useful in MPO transportation planning analyses.

Here is the Census Bureau’s statement on the usefulness of PUMAs, from the “Final Criteria” document:

"In addition to PUMS data publication, as the ACS was developed and implemented after the 2000
Census, standard PUMAs were adopted as a basic tabulation geographic entity to present summary
data. This was in response to concerns raised by SDCs and other stakeholders that the minimum
population thresholds for tabulation and dissemination of 1-year and 3-year ACS data (65,000 and
20,000 persons, respectively) would limit the availability of data for the predominantly rural portions of
states as well as for many counties. PUMAs met these population size requirements for all ACS data
tabulations and their adoption resulted in a substantially larger community of PUMA data users, many
of whom do not use PUMS files. This sustained interest in PUMA geography and associated data is
expected to continue, therefore the PUMA criteria and guidelines for the 2020 Census are intended to
help maintain a stable and comparable dataset.”

[from: Final Criteria for Public Use Microdata Area for the 2020 Census and the American Community Survey]

Note that the current set of Census 2020 PL 94-171 data files do NOT have PUMAs as a standard summary level. This is because the Census 2020 includes the 2020 Census Tracts, and the current PUMAs are based on the 2010 Census Tracts.

My recommendation for MPO staffs. To me this is a GIS-heavy process:

1. Map the Census 2010 Census Tracts and PUMAs.

2. Map the Census 2020 Census Tracts. Ideally the 2020 tracts nest within the 2010 tracts, but boundaries do indeed change.

3. Develop an equivalency between 2020 Census Tracts and 2010 PUMAs.

4. Use PL 94-171 data to get Census 2020 census tracts, and aggregated to approximate the 2010 PUMAs.

5. If the county is > 200,000 population, consider how to best re-draw PUMA boundaries.

6. It’s a jigsaw puzzle, where none of the potential PUMAs can be less than 100,000. Consider this as “redistricting for MPOs"

7. Involve local actors who are interested: counties, cities, academics, nonprofits, etc.

8. Consider the Bureau’s advice on “stable and comparable dataset”… Sometimes you may just keep the old PUMAs!

Hope this is of interest:

Chuck Purvis, Hayward, California

Caution! This email was sent from an external source. Do not click any links or open attachments unless you trust the sender and know the content is safe.