Federal agencies use several definitions to describe what constitutes urban and rural areas, but the Census Bureau’s upcoming 2020 Census Urban and Rural Classification is arguably the most important.

On December 29^th, the agency will release its decennial list of urban areas, boundary maps and other related materials. The long-anticipated products comes after final delineation criteria were published on March 24, 2022.

Under the new rules, the boundaries released this decade may reflect urban areas that are smaller in size, and in some cases could have lower population.

That could come as the result of technical changes to the delineation procedures to reel in what the Census Bureau considered to be an overextension of urban territory in prior decades. The agency also increased population thresholds for inclusion in the list. That means that some number of smaller urban areas with a population of between 2,500 and 5,000 people, that had been previously designated as urban clusters, won’t be included in this go-around.

Overview of Changes for the 2020 Release

The U.S. Census Bureau has overseen the process of defining urban areas for more than a century. Since 1950 it has used an ever-evolving concept of densely-settled territory to include not just the urban-core, but suburban intensity developments as well.

Those changes limit decade-to-decade comparisons, but they also allow the process to incorporate new technology and data. Here’s more information on the 2020 definition and release.

Definition of urban and rural

Urban areas are densely developed territory that includes both residential and non-residential land uses, and contains at least 5,000 people or 2,000 dwellings. They are delineated using criteria based on housing unit density; the presence of large group quarters, airports and large employment centers; and the level of impervious surface from satellite imagery. To maintain consistency, data used for the delineations are publicly available and have coverage for the entire nation.

Urban areas contain a core with at least 425 housing units per square mile and peripheral area containing at least 200 housing units per square mile. They must also contain a densely settled nuclei built at 1,275 housing units per square mile.

Figure 1:  Examples of housing unit density used in the urban area delineation

Rural areas include any territory that is not classified as urban.

What data will be released?

The December 29^th release will include three products.

1. Lists of urban areas with 2020 Census population, housing units and land area
2. Urban areas maps
3. Shapefiles

Key changes from 2010 delineation

The procedure for delineating urbanized areas is revised each decade as new data, technology and other considerations are weighed through a series of federal register notices. Several important changes were made this decade:

• Minimum size increased to 5,000 people or 2,000 housing units; this is up from 2,500 people in 2010
• Remove distinction between urban areas (>50,000 population) and discontinue use of the the term urban cluster (<50,000 population)
• Areas are delineated housing unit density, not population density, to account for vacancy and seasonal units
• Discontinue practice of connecting of low-density corridors to discontiguous outlying blocks along the urban area boundary
• Incorporate areas containing employment-centers with at least 1,000 jobs

How are urban area and rural data used?

The characterization of urban and rural territory is complex, but the results are used to guide a variety of planning programs, determine program eligibility and used for statistical research:

• Distribution of federal transportation funds to Metropolitan Planning Organizations where population exceed 50,000
• Designation of core-based statistical areas, including Metropolitan/Micropolitan Statistical Areas by the U.S. Office of Management and Budget
• US Department of Agriculture uses the data as inputs in several “rural” definitions