The USDA, Economic Research Service’s (ERS) Commuting Zones (CZs) are intended to represent labor markets where rural people live and work. CZs are one of several delineations that may be used to represent labor markets, each of which has features that make it more appropriate for some applications and less appropriate for others. This User’s Guide compares the features of commuting zones, counties, and metropolitan and micropolitan statistical areas to guide users in choosing the appropriate delineation for their application.
Counties and county-equivalents are commonly used for regional research, policy, and other applications because they are one of the smallest geographic units for which reliable data are readily available from public data sources. They are also recognizable, relatively stable over time, and often reflect functional governmental units. Their combination of granularity and reliability make them particularly useful when users wish to focus on the characteristics of rural residents, businesses, or communities, particularly over time.
However, county boundaries do not necessarily capture the daily movements and activities of rural residents. Their boundaries are largely political in nature and do not prevent people from traveling between counties for work or to access different goods and services. Because it is relatively common—particularly in the Eastern United States—for people to commute between their county of residence and other counties for work and commerce, larger geographic units that reflect labor markets are often desirable to capture what residents and businesses in a labor market may access.
One of the most widely used labor market delineations is the OMB’s Core Based Statistical Areas—metropolitan (metro) and micropolitan (micro) areas. This delineation groups together counties that contain part of a shared urban core (of at least 10,000 people for micro areas and at least 50,000 people for metro areas) and all adjacent counties with high commuting rates to or from the core counties. This results in geographic units that are better at capturing the jobs, goods, and services available within an area of economic activity than individual counties are. Like counties, metro and micro areas are relatively recognizable and data are readily available from public data sources.
Because of how they are created, metro and micro areas exclude counties that do not have a strong commuting connection to an urban core of at least 10,000 people. This means that 61 percent of counties and county equivalents in the United States and Puerto Rico are not represented in the delineation. These excluded counties tend to be the most rural counties that neither have nor are near an urban area of at least moderate size. Therefore, metro and micro areas cannot be used to examine labor market conditions in the most rural areas of the United States.
Commuting zones have features of both counties and metro and micro areas. Like counties, CZs cover the entire area of the United States and Puerto Rico, enabling extensive analysis of rural areas. Like metro and micro areas, CZs are county groupings that are based on commuting patterns and are intended to identify labor markets. CZs allow users to better represent the jobs, goods, and services that rural residents have access to. CZs may also be used to better understand the labor force available to rural employers within the commuting zone.
One limitation of commuting zones is that they are not easily recognizable. That is, it may not be obvious to members of the public which CZ they live in or why a county is in one CZ and not another. Additionally, there is no requirement that there be an urban core within a CZ. As a result, the character of CZs can vary significantly, and users should carefully consider whether comparing CZs is appropriate, given the potential variation in characteristics.
Ultimately, whether commuting zones, counties, or metro and micro areas are the best geographic unit depends on the needs of each project or application. For situations in which a high level of spatial granularity is required, counties are likely the best choice of the three delineations discussed here. Metro and micro areas may be best suited to applications that focus on urban economic activity, particularly ones requiring core-periphery relationships. Finally, CZs are likely the best choice when an application is focusing on labor patterns, particularly in rural parts of the United States.