urban v rural

A definitive answer from the Census Bureau Geography Division would be useful, but my understanding is that urbanized areas ("urban") are independent of census tract (and census block group) geographies. This means that any given census tract might be split into an urbanized area portion and a rural (non-urban) portion.

A GIS approach could be to overlay urbanized areas over census tracts, and assign a tract as either urban or rural based on the land area (maybe population) within each tract portion.

Another approach, which I've favored, is to calculate the tract-level (or block group-level) gross population density (total population divided by land area in square miles).

Population densities of 1,000 ppsm or greater are considered urban; less than 1,000 persons per square mile, rural.

In my previous career, we used a six category system:

0 - 500 ppsm = Rural

500 - 1000 = Rural-Suburban

1000 - 6000 = Dispersed Suburb

6000 - 10000 = Dense Suburb

10000 - 20000 = Urban

20000 + = Urban Core

Here, suburban tracts would still be considered "urban" if the dichotomy is merely "urban" vs "rural".... The key value is the 1,0000 persons per square mile density. This value comes up again and again in Census Bureau documentation on urban and urbanized area.

We also used workers at tract-of-work to augment population density. Some census tracts are suburban in nature by their population density (e.g., financial district in San Francisco) but are urban core to the extreme when examining both population and job density. On the other hand, the Golden Gate Park (in SF) census tract is rural as could be, though it's smack dab in the middle of a large urbanized area.

In my analysis of San Francisco Bay Area density from the 2010 Census, I showed 83.9 percent of the land area and 7.8 percent of the population in block groups of less than 1,000 ppsm. Suburban was 10.5 percent of land area; 54.1 percent of total population; and Urban was 2.4 percent of the land area and 37.9 percent of the total population. (I haven't yet updated my analysis for 2020. Retirement means no deadlines.)

My recommendation would be to assign a census tract an urban or rural code based on 1,000 persons per square mile (ppsm) density, and then compare the coverage of those census tracts to available urbanized area boundaries.

Chuck

Dear Chuck,

Thanks for the thoughtful and thorough reply. Tougher than I thought !  For those of you who are following this thread here are some references for the 2020 census definitions:  Federal Register Notice (3/24/2022):  https://www.govinfo.gov/content/pkg/FR-2022-03-24/pdf/2022-06180.pdf  History of Urban designation: https://www2.census.gov/geo/pdfs/reference/ua/Century_of_Defining_Urban.pdf  Urban and Rural release dates  https://www.census.gov/programs-surveys/geography/guidance/geo-areas/urban-rural.html  FAQ https://www2.census.gov/geo/pdfs/reference/ua/2020_Urban_Areas_FAQs.pdf

Most of the release dates are in the Dec 2022 to Jan 2023 time frame. shapefiles: Dec 2022 

As far as geography goes (from FAQ) Urban areas are defined primarily based on housing unit density measured at the census block level. The basic criteria is 425 housing units per square mile but there are additional criteria used to minimizes the number of noncontiguous pieces of an area.  The census leaves it up to you to decide if their criteria is suitable for your intended use.

Hope this helps those who are interested in the urban/rural designation.

Just as an FYI.  I'm doing some work on CDC data. The CDC urban/rural scheme documentation is here https://www.cdc.gov/nchs/data/series/sr_02/sr02_166.pdf  It seems to be based on a Metropolitan Statistical Area / Urban Cluster scheme.  The reference is based on the 2010 areas and the documentation was released in April 2014 so there should be an update for the 2020 census areas coming along at some point.

You've got a useful list of resource links above. In addition, for those who like a good video, here's a new one describing how urban areas are defined: https://www.youtube.com/watch?v=elZu3L3xahg&feature=youtu.be 

When replying, they appeared below. Once posted the links are *above!* Have corrected my comment accordingly.

Beth Jarosz where are the links "below"?

Ten years ago - and again, coming soon, December - there was (will be) a new set of Census blocks files that add the Urban/Rural determination for each block. If Urban, blocks will also have a UA ID for the Urban Area in which they belong. So Census Bureau's determination happens at block level, not tract level. (I think that's your question David)

There's a short slidedeck (9 slides) here https://docs.google.com/presentation/d/1nSuDMXaVSva7vBEeZUfiS40apWHOqr4J/edit?usp=sharing&ouid=100562141110200427638&rtpof=true&sd=true  to explain the whole process for Urban designation. It's probably a quicker, clearer read than the FR Notice.  [PS: oh... you'll have to download that file to get the slide animation on slide 6 to show up.]

Enjoy

--Todd Graham

Todd, can you provide any insight as to the differences between this slide deck and the 2020 urban/rural definition at https://www.census.gov/programs-surveys/geography/about/glossary.html#par_textimage_29 ?

For the 2020 Census, the Census Bureau classified as urban all territory, population, and housing units located within densely developed Urban Areas of at least 2,500 people. The Census Bureau delineates Urban Area boundaries that represent densely developed territory, encompassing residential, commercial, and other nonresidential urban land uses. In general, this territory consists of areas of high population density and urban land use resulting in a representation of the “urban footprint.” Rural consists of all territory, population, and housing units located outside Urban Areas. For the 2010 Census and American Community Survey (ACS) data tabulations during the decade leading up to 2020, the Census Bureau identified two types of Urban Areas: urbanized areas of at least 50,000 people and urban clusters of at least 2,500 and less than 50,000 people. 

This is the same as the 2010 UR classification.

However, the slide deck you linked uses different criteria (slide 3):

>= 425 dwelling units/sq. mi. (equivalent to > 0.66 units/acre)
Or substantial impervious surface: >= 20%
Or group quarters facility and >= 500 pop/square mile

Moreover, the process for defining urban areas is substantially different (slide 4):

1. Aggregating Urban blocks into Urban Areas:
An initial contiguous core area with >= 500 dwelling units
Contiguous Urban blocks
2. Add-on nearby Urban blocks:
Any number of “hops” <= 0.5 mile over land area
And up to one “jump” of 0.51 – 1.5 miles over land area
3. Check population: Urban Area must have >= 5,000 population

It looks as though: A. the minimum population for an Urban Area has dropped from 50,000 in 2010 to only 5,000 in 2020; and B. Urban Clusters (2,500 to 50,000 population in 2010) are no longer a statistical entity for 2020. Can you confirm this? Who should I believe -- the Bureau's web page, or the slideshow you posted?

Glenn

"Who should you believe?" GREAT question. 

You should believe the Federal Register Notice published March 2022  https://www.federalregister.gov/documents/2022/03/24/2022-06180/urban-area-criteria-for-the-2020-census-final-criteria 

It is remarkable that the census.gov page you pointed to has not been updated with current definitions. But the FRN has the force of a regulatory decision.

Oh... your other question was about "urban clusters."  Census Bureau proposed and then decided that there was no meaningful distinction between an urban area and an urban cluster -- other than size -- so why call them different things? The two concepts were collapsed into the unified concept: urban areas. And the minimum qualifying population was set at (min.) 5,000. 

PS:  I discuss, toward the end of my slideshow, there are some nuanced distinctions between Census UA's and FHWA UZA's. One big point: An urban area still must have 50,000+ population to qualify as the service area for a transportation-planning UZA.  (But that's a FHWA criterion, not Census criteria.) 

--Todd Graham
  Metropolitan Council

More PS: In my opinion... Census Bureau should be more like IPUMS = send you a "thanks" and a coffee mug when you find errors on the census.gov website.

Adding some clarification...

This is not accurate:

"A. the minimum population for an Urban Area has dropped from 50,000 in 2010 to only 5,000 in 2020"

Nor is this:

"there was no meaningful distinction between an urban area and an urban cluster"

In both cases, it'd be more accurate if you replace "urban area" with "urbanized area." They're not the same thing. (I'd say that the ease which these terms can be confused is yet another good reason for doing away with one of them!)

In the 2000 and 2010 definitions, urbanized areas and urban clusters are both types of urban areas. Urbanized areas have more than 50,000 residents and urban clusters have 2,500 to 49,999. As I understand, there will no longer be any such distinction. They'll all just be "urban areas".

The previous minimum threshold for urban areas was 2,500. It's going up to 5,000 residents or 2,000 housing units.

Jonathan Schroeder said:

This is not accurate:

"A. the minimum population for an Urban Area has dropped from 50,000 in 2010 to only 5,000 in 2020"

So, you are saying that the slide deck also contains inaccurate info? Great.

Yes, this bit in the slide deck:

"Urban Area must have >= 5,000 population"

Is contradicted by this in the FRN:

"An area will qualify as urban if it contains at least 2,000 housing units or has a population of at least 5,000."

As Todd said in his last message, the FRN is the official source, and there's a good summary of the criteria there.

And now I realize I confused things further by saying that using the term "urbanized area" in this statement would make it accurate:

A. the minimum population for an Urban Area has dropped from 50,000 in 2010 to only 5,000 in 2020

The 2010 minimum population threshold for urbanized areas had been 50,000. But that concept is going away entirely with 2020 definitions. The corrected statement is:

A. the minimum threshold for an Urban Area has increased from 2,500 population in 2010 to either 5,000 population or 2,000 housing units in 2020

Hooo boy. Drama.

The slideshow I shared -- this https://docs.google.com/presentation/d/1nSuDMXaVSva7vBEeZUfiS40apWHOqr4J/edit?usp=sharing&ouid=100562141110200427638&rtpof=true&sd=true  -- is my attempt to summarize a 9,000 words FR Notice into 6 slides. It's a communication vehicle for explaining the whole thing to planners who do not want (or need) to read 9,000 words. 

At this time I'm not aware of anything egregiously "wrong" in the slideshow. I did -- I confess -- take some liberties in turning the 9,000 words into 6 slides. Like Jonathan says: the new minimum for an Urban Area is >= 5,000 population OR >= 2,000 housing units. I left out that part to keep things simple for my audience.

I also glossed over or totally skipped nuances like... the crucial difference between a "Core Eligible Block Aggregation" and "Other [non-Core] EBAs."  Certainly the geographers at USCB need to understand these differences; Transpo planners? not so much.

If there are true errors in the slideshow, let me know here, or with an email, I'm happy to hear from you.

And again, the FR Notice is available https://www.federalregister.gov/documents/2022/03/24/2022-06180/urban-area-criteria-for-the-2020-census-final-criteria for anyone wanting the long read.

cheers,

Todd Graham