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Suburban development


Economist Leah Platt Boustan examines
'white flight' in postwar suburbanization

In 1968, the Kerner Commission, charged with investigating the riots sweeping through the nation’s cities, came to the stark conclusion that America was “moving toward two societies, one black, one white—separate and unequal.” To this list, the Commission might have added: “urban and suburban.” Metropolitan areas were more racially segregated in 1970 than at any point in the century (Glaeser and Vigdor, 2001 [pdf]), and, increasingly, segregation coincided with jurisdictional lines, with blacks remaining in the center city while whites moved to independent towns in the suburban ring (Fischer, et al., 2004 [pdf]).[1]

Leah Platt Boustan

Leah Platt Boustan

Inter-jurisdictional segregation not only curtails day-to-day interactions between blacks and whites, but also contributes to racial disparities in access to public resources, of which education is perhaps the most important. But, while racial segregation remains a real and potentially deleterious feature of American urban space, understanding its development requires traveling back to the end of World War II, an analytic journey undertaken by Leah Platt Boustan, then a graduate student in Harvard’s economics department and a doctoral fellow in the Multidisciplinary Program in Inequality and Social Policy (now Assistant Professor of Economics, UCLA). At this moment in history, a pent-up demand for new housing, put on hold by war mobilization, and strengthened by the subsequent baby boom, was busily being filled on the suburban periphery. New road construction, first by states and later by federal interstate highways, was enabling longer commutes to the center city. Against this backdrop came a steady stream of rural blacks—over four million arrivals from 1940 to 1970—abandoning agricultural labor for the industrial promise of the North and West.

Boustan wondered whether this influx of poor, black migrants, and the resulting increase in urban racial diversity, were important motivations for white suburbanization. Is there historical evidence of “white flight,” or can the postwar suburbanization be adequately explained by economic and demographic factors, such as rising real incomes, larger families and lower commuting costs? And, why would white households want to leave diverse cities in the first place, given that segregated central cities offered a large array of predominately white neighborhoods in which to live?[2]

Figure 1 plots the relationship between changes in the black population share of the central city, driven primarily by black in-migration, and the share of whites who live in the suburban ring for one postwar decade (1950-1960). The data represent 68 large metropolitan areas in the North and West. While the correlation is quite strong, Boustan reasoned that this pattern could be driven either by the desire of whites to escape urban diversity or by the location choices of black migrants. Migrants might be attracted to lower housing prices in the wake of white departures, or to some of the same economic factors that underlie the demand for suburbanization (for example, rising wages).

Figure 1: Click to view larger image (opens new window)

Figure 1: Click to view larger image.

One way to disentangle these two alternatives is to watch how white households respond to black migrants who end up in their city for reasons unrelated to local economic conditions. Like other immigrant groups, black migrants followed family chains and well-established transportation networks out of the South. Boustan uses settlement patterns from earlier black migration (1915-34) to assign flows of postwar migrants from southern states to northern cities. Even after making this adjustment, Boustan finds that white suburbanization was sensitive to black arrivals. She estimates that, if not for new black migration, the growth in white suburbanization from 1940-1970 would have been 20 percent lower than it in fact was. These finding are described in more detail in Boustan's paper Was Postwar Suburbanization ‘White Flight?'.

After documenting the quantitative importance of “white flight,” Boustan turned to understanding why white households chose to leave diverse, but racially segregated, cities. One possibility is that, by remaining within the city limits, urban residents had to compromise with black newcomers on local policy, including the property tax rate and the composition of city spending. In addition, their children had to attend integrated public schools—particularly at the high school level—or be sent to expensive private alternatives.

Could the desire to limit these civic forms of interactions with black migrants have driven the flight to the suburbs? Boustan’s paper "Inside the Black Box of White Flight" addresses this question by asking: how much are white families willing to pay to avoid voting with or educating their children among black migrants? The desire for separation is reflected in higher prices for housing units located in predominately white jurisdictions. However, by virtue of their location, such houses also tend to have fewer black neighbors, to be located farther from the city center, and to be drawn from a newer housing stock—factors that each have an independent effect on housing prices.

To isolate the role of suburban autonomy, Boustan exploits a natural experiment that arises from the often-arbitrary division of urban space into separate jurisdictions. While the local electorate and school system change sharply at the city border, it is reasonable to assume that housing quality and neighborhood composition shift more continuously. Differences in prices for these neighboring houses can thus be attributed to a demand for suburban residence.

For this exercise, Boustan collected housing price data at the block level along 57 jurisdictional borders in 1960 and 1970. She found that housing prices fall discretely on the diverse side of these borders (Figure 2). In crossing the average border in 1970, one leaves a town that is 4.4 percent black and enters a city that is 17.6 percent black. This difference is associated with a 3.0 percent decline in housing values.

Figure 2: Click to view larger image (opens new window).

To what can we attribute this demand for homogeneity? Black migrants were poorer than existing urban residents. Some of the price gap may simply be capitalizing differences in property tax rates between rich and poor jurisdictions? (In a system of local public finance, a property-poor town has to set a higher tax rate to collect the same amount of revenue per resident). Beyond tax rates, did white residents clash with new black arrivals over the allocation of public funds, and, if so, was this disagreement a matter of race or, again, one of class? Finally, where do public schools fit in?

At the mean border, a larger black population is associated with higher property tax rates—via its effect on average income. In net present value terms, this negative annuity can account for around half of the estimated decline in housing values.

Block-level age patterns provide suggestive evidence that the racial composition of local public schools also mattered. Before the implementation of court-ordered desegregation plans in the 1970s, elementary schools were neighborhood-based, while public high schools drew from larger, and thus more diverse, areas. Correspondingly, there are fewer-than-average elementary aged children in neighborhoods with a high black share, while the presence of high school aged children is sensitive to the racial composition of the jurisdiction as a whole.

Boustan concluded that while postwar suburbanization was, in part, a response to southern black migration, white urbanites were reacting as much to the migrant’s income levels as to their race. She is currently matching the blocks in her sample to school-level racial composition data from the Office of Civil Rights to confirm the distaste for integrated public schools[3].

(November 2005)


[1] By the late 1960s, nearly 70 percent of white households in the average metropolitan area lived in the suburban ring, an increase from only 45 percent in 1940. Over the same period, the fraction of blacks living in the city center remained steady at 80 percent.

[2] Conservative estimates indicate that, in 1940, 79 percent of Census tracts in central cities were at least 90 percent white and 52 percent were 99 percent white.

[3] Sarah Reber generously shared her electronic school-level files for this project.



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