The models of urban structure help us understand where people with different social characteristics tend to live within an urban area. They can also help explain why certain types of people tend to live in particular places.

Social Area Analysis

The study of where people of varying living standards, ethnic background, and lifestyle live within an urban area is social area analysis. Social area analysis helps to create an overall picture of where various types of people tend to live, depending on their particular personal characteristics.

Social area analysis depends on the availability of data at the scale of individual neighborhoods. In the United States and many other countries, that information comes from the census. Urban areas in the United States are divided into census tracts that each contain approximately 5,000 residents and correspond, where possible, to neighborhood boundaries. The census also divides the entire United States into blocks, which are typically a collection of several dozen houses; inside urban areas, blocks are typically bounded by four streets. A block group, as the name implies, is a collection of several neighboring blocks.

Every decade the U.S. Bureau of the Census publishes data summarizing the characteristics of the residents and the housing in each tract. Annual estimates are issued through the American Fact Finder service of the census’s American Community Survey program. Examples of information the census provides at the tract level include the number of various ethnicities, the median income of all families, and the percentage of adults who finished high school.

The spatial distribution of any of these social characteristics can be plotted on a map of the community’s census tracts. Computers have become invaluable in this task because they permit rapid creation of maps and storage of voluminous data about each census tract. Relatively little is available at the block level because the number of people is so small that publishing the information could violate the privacy of individuals.

Social Area Analysis: Concentric Zones

Consider two households with the same income and ethnic background. One household lives in a newly constructed home, whereas the other lives in an older one. The concentric zone model suggests that the household in the older house is much more likely to live in an inner ring and the household in the newer house in an outer ring.

Concentric Zones in San Antonio: age of Housing

The outer ring has a higher percentage of recently built housing.

San Antonio Concentric Zone: Older Housing

Older housing is found in an inner ring.

San Antonio Concentric Zone: Newer Housing

New housing is found in an outer ring.

Social Area Analysis: Sectors

Given two households who own their homes, the sector model suggests that the household with a more modest income is unlikely to live in the same sector of the city as the household with the higher income

Sectors in San Antonio: Income

Higher-income people tend to live in the northern sector.

Social Area Analysis: Nuclei

People with the same ethnic or racial background are likely to live near each other (Figures 13-22 and 13-23).

San Antonio Multiple Nuclei

Hispanic node.

Multiple Nuclei in San Antonio: Ethnicities

African Americans, Asian Americans, and Hispanics cluster in different nodes.

Limitations of the Models

None of the three models taken individually completely explains why different types of people live in distinctive parts of a city. If the models are combined rather than considered independently, they help geographers explain where different types of people live in a city. Putting the three models together, we can identify, for example, the neighborhood in which a high-income, Asian American owner-occupant is most likely to live.

Still, critics point out that the models are too simple and fail to consider the variety of reasons that lead people to select particular residential locations. Because the three models are all based on conditions that existed in U.S. cities during the mid-twentieth century, critics also question their relevance to contemporary urban patterns in the United States or in other countries.

Pause & Reflect 13.2.2

Would you expect the distribution of families with children to follow most closely the concentric zone, sector, or multiple nuclei model? Why?