Suburbanization is one aspect of the more general process of the expansion and spatial reorganization of metropolitan settlements. Settled areas that are beyond the historical boundaries of what have been considered cities but still are clearly functionally linked to the cities or may not be considered suburban. What is suburban is a matter of social definition. For example, when small cities are enveloped by the expansion of larger cities, at what point should they be considered suburbs, if they should be called suburbs at all? As some cities extend their boundaries outward, will the newly settled areas not be considered suburban if they are within the new boundaries?
Many researchers in the United States have chosen to adopt conventions established by the U.S. Bureau of the Census. The term ”suburban” refers to the portion of a metropolitan area that is not in the central city. This definition depends on what is defined as metropolitan and central city, and those definitions change over the years. Such changes are not simply technical adjustments; they respond (among other criteria) to assumptions about what cities and suburbs are. For example, as many U.S. ”suburbs” have become employment centers in the last two decades, altering traditional patterns of commuting to work, Census Bureau scientists have adjusted the definition of ”central city” to include some of those peripheral areas.
For many purposes, it may be preferable to avoid these categories altogether. ”Suburban” may be intended to reflect distance from the city center, recency of development, residential density, or commuting patterns—all of which can be measured directly. The main substantive rationale for accepting definitions tied to the juridical boundaries of cities is to emphasize the differences between cities and suburbs (and among suburbs) that are related to municipal governance. An important class of issues revolves around disparities in public resources: In what parts of the metropolis are taxes higher, where are better schools available, where is police protection greater? What are the effects of these differences on the opportunities available to people who live in different parts of the metropolis? Another dimension concerns local politics: How do localities establish land use and budget policies, and what are the effects of those policies on growth?
Because many suburban residents have worked in central cities while paying taxes in the suburbs, John Kasarda has described the city-suburb relationship in terms of ”exploitation.” Political scientists in particular have studied this issue in terms of arguments for the reform of structures of metropolitan governance. The normative implications of their arguments have explicit ideological underpinnings. Some, such as Dennis Judd, emphasize the value of equality of life chances and interpret differences between cities and suburbs as disparities; others (public choice theorists such as Elinor Ostrom) emphasize freedom of choice and interpret differences as opportunities for the exercise of choice.
Sociologists on the whole have been less willing to be proponents of metropolitan solutions and have shown more interest in the causes than in the consequences of suburbanization. Nevertheless, there are differences in theoretical perspective that closely parallel those in political science, and they hinge in part on the importance of political boundaries and the political process. The main lines of explanation reflect two broader currents in sociological theory: Structural functional-ism is found in the guise of human ecology and neoclassical economics, and variants of Marxian and Weberian theory have been described as the ”new” urban theory.
Ecologists and many urban economists conceptualize suburbanization as a process of decentralization, as is reflected in Burgess’s (1967) concentric-zone model of the metropolis. Burgess accepted the postulate of central place theory that the point of highest interaction and most valued land is naturally at the core of the central business district. The central point is most accessible to all other locations in the metropolis, a feature that is especially valuable for commercial firms. At the fringes of the business district, where land is held for future commercial development, low-income and immigrant households can compete successfully for space, though only at high residential densities. Peripheral areas, by contrast, are most valued by more affluent households, particularly those with children and a preference for more spacious surroundings.
The key to this approach is its acceptance of a competitive land market as the principal mechanism through which locational decisions are reached. More specific hypotheses are drawn from theories about people’s preferences and willingness (and ability) to pay for particular locations or structural changes (e.g., elevators, transportation technology, and the need for space of manufacturers) that affect the value of a central location. Many researchers have focused on gradients linking distance from the center to various compositional characteristics of neighborhoods: population density (Treadway 1969), household composition (Guest 1972), and socioeconomic status (Choldin and Hanson 1982). Comparatively little research has been conducted on the preferences of residents or the factors that lead them to select one location or another.
Other sociologists have argued that growth patterns result from conscious policies and specific institutional interventions in the land and housing markets. Representative of this view is the study done by Checkoway (1980), who emphasizes the role of federal housing programs and institutional support for large-scale residential builders in the suburbanization process of the 1950s. The move to suburbs, he argues, was contingent on the alternatives offered to consumers. The redlining of inner-city neighborhoods by the Federal Housing Administration, its preference for large new subdivisions, and its explicit discrimination against minority home buyers are among the major forces structuring these alternatives.
There have been few studies of the housing market from an institutional perspective, although the restructuring of real estate financing and the emergence of new linkages between large-scale developers and finance capital have begun to attract attention. More consideration has been given to the explicitly political aspects of land development (Logan and Molotch 1987). Following Hunter (1953), who believed that growth questions are the ”big issue” in local politics, later studies found that the most powerful voices in local politics are the proponents of growth and urban redevelopment and, in this sense, that a city is a growth machine.
In applying this model to suburbs, most observers portray suburban municipalities as ”exclusionary.” Suburban municipalities have long used zoning to influence the location and composition of land development. Since environmentalism emerged as a formidable political movement in the early 1970s, it has become commonplace to hear about localities that exercise their power to preserve open space and historic sites by imposing restraints or even moratoriums on new development. The ”no-growth movement” is a direct extension of earlier exclusionary zoning policies.
SOCIOECONOMIC DIFFERENCES BETWEEN CITIES AND SUBURBS
These two theoretical perspectives can be illustrated through their application to research on socioeconomic differences between cities and suburbs. It is well known that central cities in most metropolitan regions have a less affluent residential population than do the surrounding suburbs. There is much debate, however, whether this class segregation between cities and their suburbs represents a natural sorting out of social classes through the private market or whether its causes are political and institutional. Similar debate surrounds the phenomenon of differentiation within suburbia, where there is great variation in economic function, class and racial composition, and other characteristics of suburbs.
Research from an ecological perspective has stressed a comparison between the older, larger, denser cities of the North and the more recently growing cities of the South and West. The principal consistent findings have been that (1) the pattern of low central city relative to suburban social status is more pronounced in older metropolitan regions but that (2) controlling for metropolitan age, there appears to be a universal generalization of this pattern over time (Guest and Nelson 1978). These sociologists propose that suburbs have natural advantages over central cities. For example, their housing stock is newer, their land is less expensive, and they are more accessible to freeways and airports. The socioeconomic differences between cities and suburbs reflect those advantages.
Others argue that disparities are generated primarily by political structures that allocate zoning control and responsibility for public services to local governments and require those governments to finance services from local sources such as taxes on real property. They propose that the typical fragmentation of metropolitan government creates the incentive and opportunity for suburbs to pursue exclusionary growth policies (Danielson 1976).
Seeking to test these theories, Logan and Schneider (1982) found greater disparities in metropolitan areas where central cities were less able to grow through annexation (thus where suburban municipal governments were more autonomous) and where localities were more reliant on local property taxes (hence had greater incentive to pursue exclusionary policies). They also found a significant racial dimension: Greater disparities were evident in both 1960 and 1970 in metropolitan areas in the North with a larger proportion of black residents. (This did not hold for the South and West, however.) This disparity is due both to the concentration of lower-income blacks in central cities and to a greater propensity of higher-status whites to live in suburbs in those metropolitan areas. This finding is reinforced by Frey (see Frey and Speare 1988; Shihadeh and Ousey 1996), who reported that the central-city proportion of black residents is a significant predictor of white flight, independent of other causes.
If suburbs follow exclusionary growth policies, it seems counterintuitive that suburbs experienced much more rapid growth than did cities in the postwar decades. The findings on city-suburb disparities, of course, indicate that exclusion has selective effects. Nevertheless, it is surprising that in a study of northern California cities, Baldassare and Protash (1982), found that communities with more restrictive planning controls actually had higher rates of population growth in the 1970s. Similarly, Logan and Zhou (1989) found that suburban growth controls had little, if any, impact on development patterns (population growth, socioeconomic status, and racial composition). In their view, the exclusionary policies of suburbs may be more apparent than real. The more visible actions, such as growth moratoriums, often are intended to blunt criticisms by residents concerned with problems arising from rapid development. Unfortunately, few studies have looked in depth at the political process within suburbs; there is as little direct evidence on the role of local politics as there is on the operation of the land market. Most research from both the ecological and the political-institutional perspectives has inferred the processes for controlling growth from evidence about the outcomes.
SUBURBANIZATION OF EMPLOYMENT
A central problem for early studies of suburban communities was to identify the patterns of functional specialization among them. It was recognized that older industrial satellites coexisted with dormitory towns in the fringe areas around central cities. Both were suburban in the sense that they were integrated into a metropolitan economy dominated by the central city. Their own economic role and the nature of the populations they housed were quite distinct, however. The greatest population gains in the 1950s occurred in residential suburbs, communities that were wealthier, younger, newer, and less densely settled than the towns on the fringes of the region that had higher concentrations of employment. Schnore (see Schnore and Winsborough 1972) distinguished ”suburbs” from ”satellites” to acknowledge these different origins.
The metaphors of suburbs and satellites reflected the reality of early postwar suburbanization, a period when established towns and small cities were surrounded by successive waves of new subdivisions. Those metaphors are no longer appropriate. Since the late 1950s, the bulk of new manufacturing and trade employment in the metropolis has been located in small and middle-sized cities in the suburban ring (Berry and Kasarda 1977, chap. 13). Downtown department stores compete with new suburban shopping malls. The highly developed expressway network around central cities frees manufacturing plants to take advantage of the lower land prices and taxes and the superior access to the skilled workforce offered by the suburbs. For the period 1963-1977, in the largest twenty-five metropolitan areas, total manufacturing employment in central cities declined by about 700,000 (19 percent), while their suburbs gained 1.1 million jobs (36 percent). At the same time, total central-city retail and wholesale employment was stagnant (dropping by 100,000). Trade employment in the suburbs increased 1.8 million (or 110 percent) in that period. Thus, total employment growth in the suburbs outpaced the growth of population (Logan and Golden 1986). This is the heart of the phenomenon popularized by Garreau (1991) as the creation of ”Edge City.”
How has suburbanization of employment affected suburban communities? According to microeconomic and ecological models, locational choices by employers reflect the balance of costs and benefits of competing sites. New employment maintains old patterns because the cost-benefit equation is typically stable, including important considerations such as location relative to workforce, suppliers, markets, and the local infrastructure. In the terms commonly used by urban sociologists, this means that communities find their ”ecological niche.” Stahura’s (1982) finding of marked persistence in manufacturing and trade employment in suburbs from 1960 to 1972 supports this expectation. Once it has ”crystallized,” the functional specialization of communities changes only under conditions of major shifts in the needs of firms.
In this view, to the extent that changes occur, they follow a natural life cycle (Hoover and Vernon 1962). Residential suburbs in the inner ring, near the central city, tend over time to undergo two related transformations: to higher population density and a conversion to nonresidential development and to a lower socioeconomic status. Thus, inner suburbs that gain employment are—like older satellites—less affluent than residential suburbs.
By contrast, those who emphasize the politics of land development suggest very different conclusions. A growing number of suburbs perceive business and industry as a significant local resource. Once shunned by the higher-status suburbs, they now contribute to property values and the local tax base. Prestigious communities such as Greenwich, Connecticut, and Palo Alto, California, house industrial parks and corporate headquarters. The ”good climate for business” they offer includes public financing of new investments, extensive infrastructure (roads, utilities, parking, police and fire protection), and moderate taxes (Logan and Molotch 1987).
Competition among suburbs introduces a new factor that has the potential to reshape suburban regions. Schneider (1989) reports that location of manufacturing firms is affected by the strength of the local tax base, suggesting that wealthy suburbs are advantaged in this competition. Logan and Golden (1986) find that newly developing suburban employment centers have higher socioeconomic status, as well as stronger fiscal resources, than other suburbs; this is a reversal of the pattern of the 1950s.
The suburbanization process also increasingly involves minorities and immigrants, and the incorporation of those groups into suburban areas has become an important topic for research on racial and ethnic relations. As Massey and Denton (1987) document, the rate of growth of nonwhites and Hispanics in metropolitan areas is far outstripping the rate of growth of non-Hispanic whites. Much of this growth is occurring in suburbs. During the 1970s, for example, the number of blacks in the non-central-city parts of metropolitan areas increased 70 percent compared with just 16 percent in central cities, and the number of other nonwhites in those locations shot up 150 percent compared with approximately 70 percent in central cities. One reason for the rapidly increasing racial and ethnic diversity of suburbs may be that some new immigrant groups are bypassing central cities and settling directly in suburbs. Equally important is the increasing suburbanization of older racial and ethnic minorities, such as blacks (Frey and Speare 1988).
This phenomenon has encouraged researchers to study suburbanization as a mirror on the social mobility of minorities. Consistent with classical ecological theory, suburbanization often has been portrayed broadly as a step toward assimilation into the mainstream society and a sign of the erosion of social boundaries. For European immigrant groups after the turn of the century, residential decentralization appears to have been part of the general process of assimilation (Guest 1980).
Past studies have found that suburbanization of Hispanics and Asians in a metropolitan area is strongly associated with each group’s average income level (Massey and Denton 1987, pp. 819820; see also Frey and Speare 1988, pp. 311-315). Further, again for Hispanics and Asians, Massey and Denton (1987) demonstrate that suburban residence typically is associated with lower levels of segregation and, accordingly, higher probabilities of contact with the Anglo majority. However, these and other authors report very different results for blacks. Black suburbanization is unrelated to the average income level of blacks in the metropolitan area and does not result in higher inter-group contact for blacks. The suburbanization process for blacks appears largely to be one of continued ghettoization (Farley 1970), as is indicated by high and in some regions increasing levels of segregation and by the concentration of suburban blacks in communities with a high incidence of social problems (e.g., high crime rates), high taxes, and underfunded social services (Logan and Schneider 1984; Reardon 1997).
These findings regarding black suburbanization have been interpreted in terms of processes that impede the free mobility of racial minorities: steering by realtors, unequal access to mortgage credit, exclusionary zoning, and neighbor hostility (Foley 1973). Home ownership indeed may be one of the gatekeepers for suburban living. Stearns and Logan (1986) report that blacks were less likely to live in suburban areas where higher proportions of the housing stock were owner-occupied.
Further evidence is offered by Alba et al (1999), who based their conclusions on an analysis of individual-level data from the 1980 and 1990 censuses. They find that suburban residence is more likely among homeowners and persons of higher socioeconomic status. There are strong effects of family status (marriage and the presence of children in the household), but for many immigrant groups, measures of cultural assimilation (English language use, nativity, and period of immigration) have declining relevance for suburban location. Assimilation traditionally has been a major part of the suburbanization process for most groups, especially those arising out of immigration, but large pockets of relatively new immigrants have now appeared in the suburban ring.
Parallel results are found for the racial and ethnic sorting process within a suburban region (the New York-New Jersey suburban region, as reported by Logan and Alba 1993; Alba and Logan 1993). Two sorts of analyses were conducted. First, members of different racial and ethnic groups were compared on the average characteristics of the suburbs in which they resided. Second, regression models were estimated for members of each major racial or ethnic group to predict several of these indicators of place advantages or community resources.
There are important differences between whites, blacks, Hispanics, and Asians in regard to the kinds of suburbs in which they live. As some researchers have suspected, suburban Asians have achieved access to relatively advantaged communities that are similar in most respects to those of suburban non-Hispanic whites. Hispanics in the New York region have not. Suburban Hispanic by and large live in communities that are about the same as black suburbs: communities with low average income levels and low rates of home ownership and, perhaps more important, high crime rates (Alba et al. 1994).
Is the disadvantage of blacks and Hispanics attributable to individual qualities of group members, or do these groups face collective disadvantages? Analysis of individual characteristics that may predict the quality of the suburb in which one resides shows that the same location process does not apply equally to all minorities. The pattern for whites, who are relatively advantaged in terms of access to community resources, lends clear support to assimilation theory. Human capital and indicators of cultural assimilation are strongly associated with access to higher-status suburbs. The same can be said of Asians (who are relatively advantaged overall), with the exception that cultural assimilation variables seem not to be important for Asians.
The results for blacks call attention to processes of racial stratification. Even controlling for many other individual characteristics, blacks live in suburbs with lower ownership and income levels than do non-Hispanic whites. Further, most human capital and assimilation variables have a smaller payoff for blacks than they do for whites. The findings for Hispanics are supportive of the assimilation model in several respects. Hispanics gain more strongly than whites do from most human capital characteristics; therefore, at higher levels of socioeconomic achievement and cultural assimilation, Hispanics come progressively closer to matching the community resources of whites. It should be noted, however, that Hispanics begin from a lower starting point and that black Hispan-ics face a double disadvantage that is inconsistent with an assimilation perspective.
LOOKING TO THE FUTURE
Suburbanization continues to be a key aspect of metropolitan growth and is perhaps of growing importance in the global era (Muller 1997). The political boundaries between cities and suburbs accentuate interest in substantive issues of metropolitan inequality. They also create special opportunities for theories of urbanization to go beyond economic models and incorporate an understanding of the political process. Research on suburbanization has been most successful in describing patterns of decentralization and spatial differentiation. The movements of people and employment and the segregation among suburbs by social class, race, ethnicity, and family composition have been well documented. However, these patterns are broadly consistent with a variety of interpretations, ranging from those which assume a competitive land market (human ecology) to those which stress the institutional and political structuring of that market.
The principal gaps in knowledge concern the processes that are central to these alternative interpretations. Few sociologists have directly studied the housing market from the perspective of either demand (how do people learn about the alternatives, and how do they select among them?) or supply (how does the real estate sector operate, how is racial and ethnic segmentation of the market achieved, how is the complex of construction industries, developers, and financial institutions tied to the rest of the economy?). Rarely have sociologists investigated government decisions (at any level) that impinge on development from the point of view either of their effects or of the political process that led to them. Of course, these observations are not specific to research on suburbanization. It is important to bear in mind that neither the theoretical issues nor the research strategies in this field distinguish suburbanization from other aspects of the urban process.