“Rural” and “urban” are fuzzy concepts – there is no consensus among researchers and policy makers about how to define and classify the two. Research shows that there are over two dozen definitions that are currently in use by various federal agencies, let alone those employed by researchers, organizations, and local governments. The use of various definitions reflects the multidimensionality of these concepts – the defining criteria can be population size, population density, administrative boundaries, proximity to urban settings, and economic activities. In addition, researchers and policy makers face several challenges when defining/classifying rural and urban, such as defining thresholds and building blocks (geographic unit), and data availability.

The most commonly used federal definitions are those by the Census Bureau, the Office of Management and Budget (OMB), and the Economic Research Service (ERS) of the United States Department of Agriculture (USDA). The Census Bureau defines an urban area as a continuously built up territory with a total population of 2,500 or more, that is comprised of census block groups and blocks with a population density of at least 1,000 persons per square mile and surrounding blocks with an overall density of at least 500 people per square mile. All territory outside urban areas is defined as rural. This scheme is close to popular perceptions of rural and urban, or what we see from the airplane.

The OMB groups counties into metropolitan and non-metropolitan (a new micropolitian system was added in 2003) based on population size in an urbanized area and outlying counties, and commuting patterns between them. Even though the OMB explicitly states that this classification does not equate to a rural-urban classification, many researchers and policy makers use metro/non-metro interchangeably with urban/rural because county is the smallest geographic unit for which annual socioeconomic statistics are available.

The ERS of the USDA probably has the most extensive definitions of rural. Some of the popular classification schemes are the Rural-Urban Continuum Code (RUCC), the Urban Influence Code (UI), and the Rural Urban Commuting Areas (RUCA). The RUCC and UI define rural and urban along county lines, while the RUCA uses the census tract as the building block for more precise information at a finer geographical scale. These classifications define counties/census tracts by size and their degree of urbanization or proximity to metro areas.

Depending on the definition, the shares of U.S. rural population and its socioeconomic characteristics vary substantially. The need for a clear definition to produce accurate research conclusions and efficient and well-targeted government programs has encouraged researchers to create more detailed and precise definitions that go beyond the metro/non-metro dichotomy and overcome the “county trap.” Isserman’s (2005) rural-urban density typology and Waldorf’s (2006) index of relative rurality are two illustrative examples.

With so many definitions out there, which one is the “best”? The key might be a multidimensional approach, taking into account both economic activities and geographic dimensions along with population density/size that clearly delineates the boundaries between rural and urban areas, but at the same time recognizes the continuum and integration between rural and urban. Urban and rural poverty have distinct characteristics and require different policies, but they are also interlinked.

View other definitions.