Rural-Urban Commuting Area Codes - Users’ Guide

The Users’ Guide of the Rural-Urban Commuting Area (RUCA) Codes data product has two sections. The first section compares the 2010 and 2020 vintages of the RUCA code data. The second section discusses how the RUCA codes can be used to create a variety of rural-urban definitions.

Comparison of the 2010 and 2020 vintages

The vintage 2020 RUCA codes data product has some new features:

• All U.S. territories have been assigned a RUCA code. Puerto Rico’s RUCA codes were available in the vintage 2010 data, but the vintage 2020 data include American Samoa, Guam, the Marshall Islands, and the U.S. Virgin Islands in addition to Puerto Rico.
• If a census tract is part of an urban core, the associated urban area and its size category is included in the vintage 2020 data. The urban area names were not included in the vintage 2010 data. Knowing the urban area name and identifier for each census tract is similar to knowing the Core-Based Statistical Area (CBSA) name and identifier for central metropolitan or micropolitan counties.
• The destinations of the primary and secondary commuting flows are included in the vintage 2020 data but were not included in the vintage 2010 data. Knowing the destination name and identifier for each census tract is similar to knowing the outlying counties for each CBSA.

A couple of changes were also made to the coding scheme:

• Census tracts with no residents in the vintage 2020 RUCA code data are coded based on their location: metropolitan core, micropolitan core, small town core, or rural. In the vintage 2010 data, these zero population census tracts were considered “99–Not coded.” The one exception to this is tracts that have no land area (and no population). These tracts are coded as “99–Water” in the vintage 2020 data.
• The criteria used to determine whether a census tract is part of an urban core changed slightly between the vintage 2010 and 2020 data. In the vintage 2010 data, a census tract was considered part of an urban core if at least 30 percent of residents lived in a single urban area or if at least half of residents lived in any urban area. For the vintage 2020 data, a census tract is considered part of an urban core if at least 50 percent of residents lived in a single urban area. The new threshold made it more difficult for a census tract to be considered part of an urban core. See the Methods section of the Documentation page for more information on this change.

The table below shows the distribution of census tracts by vintage 2010 and vintage 2020 RUCA codes for the 50 U.S. States and Washington, DC. The differences between the two data vintages across the RUCA codes come from a couple different places. The first is natural changes to the rural-urban hierarchy through population change and subsequent changes to commuting behavior. This type of change is what would bump an urban core up (toward a metropolitan core) or down (toward a small town core) the rural-urban hierarchy. And if an urban core’s classification changes, so do the classifications of the census tracts that are economically tied to it through commuting.

The second difference is data changes. The new population threshold for 2020 urban areas results in fewer small town cores and more rural tracts in the vintage 2020 RUCA codes than in the vintage 2010 RUCA codes. Additionally, missing workplace destinations and changes in routine due to the COVID-19 pandemic may lead to smaller commuting flows between locations in the vintage 2020 data than in the vintage 2010 data. This change has the potential to affect the strength of the connections between residences and workplaces. 

Finally, the methodology changes also affected the distribution of census tracts across RUCA codes. The modified methodology resulted in the census tracts that were closest to the threshold being considered commuting tracts instead of part of the urban core. Not all of these changes can be seen in the table above. For example, the creation of new census tracts in urban cores, especially metropolitan cores, due to population growth masks the loss of census tracts due to the threshold change. However, these changes do not drastically impact the data, as about 87 percent of locations had the same RUCA codes in both the vintage 2010 and vintage 2020 data.

Flexibility in rural-urban definitions

The 2020 RUCA classification contains 10 primary and 21 secondary codes. Few, if any, research or policy applications need the full set of codes. Rather, the system allows for the selective combination of codes to meet varying definitional needs. The following combinations are not a definitive list but are meant to offer suggestions to users.

There are several aspects of the RUCA codes that can be used to modify the codes for varying definitional needs. These aspects include the size of the urban location, whether the tract is part of a central urban core or an outlying commuting tract, whether the low (10 percent) or high (30 percent) commuting threshold is used, and whether primary or secondary commuting are considered. Through different combinations of these aspects, users can create their own definitions or mirror the definitions used by government agencies.

“Central” and “outlying” are terms used to describe whether a county within a core-based statistical area (CBSA) is part of the area’s central urban core or is an outlying location economically connected to the urban core through commuting. The RUCA codes allow a similar differentiation between central urban core tracts and outlying commuting tracts. Some definitions may focus on the built urban environment by only including the central urban core tracts, while others may want to capture broader economic connections by including the outlying commuting tracts.

The outlying commuting tracts can be further distinguished by the perceived strength (share) of their economic connection to the urban core. If the stronger high commuting threshold of 30 percent is used, only high commuting tracts are considered outlying, resulting in fewer outlying tracts in the definition. Whereas, if the weaker low commuting threshold of 10 percent is used, both low and high commuting tracts are considered outlying, resulting in more outlying tracts and a broader definition of economic connectedness and urban influence. And while the primary RUCA codes only consider the strength of the largest commuting flow, the secondary RUCA codes allow users to consider all tracts that have a strong economic connection to an urban core.

The following examples illustrate the varying rural-urban definitions that can be created using the 2020 RUCA codes. Our first example is the U.S. Department of Health and Human Services, Federal Office of Rural Health Policy, which uses a 2-level scheme based on the primary commuting flow (i.e., primary RUCA codes). The scheme classifies tracts as “urban” or “rural” based on whether they are connected to (or part of) a metropolitan core.

• Urban/Metropolitan: RUCA 1–3
• Rural/Nonmetropolitan: RUCA 4–10

Another example is the closest approximation to the CBSA definition, which uses a 5-level scheme based on both the primary and secondary commuting flows. This classification only considers urban cores the same size as those in metropolitan and micropolitan statistical areas and includes all census tracts with at least 30 percent of commuters traveling an urban core.

• Metropolitan central: RUCA 1.0
• Metropolitan outlying: RUCA 1.1, 2.0, 2.1, 4.1, 5.1, 7.1, 8.1, 10.1
• Micropolitan central: RUCA 4.0
• Micropolitan outlying: RUCA 5.0, 7.2, 8.2, 10.2
• Rural/Noncore: RUCA 3.0, 6.0, 7.0, 8.0, 9.0, 10.0, 10.3

For more examples of rural-urban definitions that can be created from the RUCA codes, check the “Rural-Urban Classification Examples” document on the Overview page.