People talk a lot about segregation.  Every week it seems that news reports or some new academic finding shows that segregation is related to some salient outcome.  The traditional story of how America became segregated is that blacks moved to Northern cities in the early twentieth century and whites, aided by government mortgage programs and the development of the interstate highway, fled to suburban areas, creating cities with black and poor urban cores and wealthier and whiter suburbs.  With the flight of wealthier white residents to the suburbs, the resources available to the urban core declined, leaving minorities fewer resources and effectively creating a poverty trap. However, several aspects of this story are incomplete. First, we know very little about what (if anything) was occurring in rural areas.  Second, traditional segregation measures tell us how sorting was occurring across political units (such as wards) but does not tell us what was happening in the small communities that form neighborhoods.

While people live in political districts, it is more accurate to say that people live in neighborhoods.  We may not know the boundaries of our census tract or city ward, but we do know the people who live closest to us.  We ask a question motivated by this most basic building block of neighborhoods: how likely are black households to have white next-door neighbors? With the recent digitization of historical census manuscripts of 1880 and 1940, we developed a new measure of residential segregation that answers that question. Since federal census enumerators would go door-to-door when enumerating the residents of a community, next-door neighbors appear next to one another on the census manuscript pages. With this information, we can calculate the number of black households with white neighbors in a community. In a completely integrated community, this number should just depend on the racial proportions of the community: if thee quarters of the residents are white we would expect a black household’s neighbor to be white 75 percent of the time. If the community is completely segregated, all of the black households would be concentrated in one neighborhood: only the black households on the ends of the all-black neighborhood would have white neighbors. Our segregation index compares the actual number of black households with white neighbors to these two extremes of complete integration and segregation (Logan and Parman 2017). The resulting segregation index tells us the extent to which households tend to sort themselves within a community given the overall racial composition of the community. This new measure does not depend on boundaries like wards or census tracts, can be calculated at any geographic level, and serves as a much stronger proxy for social interaction between races than traditional segregation measures.

When we apply this new measure to the entire United States in 1880 and 1940, a period encompassing the Great Migration of black Americans from the South to the North, several striking features of American residential segregation emerge. Consistent with the story told by traditional segregation indices, residential segregation in urban areas rose dramatically throughout the US over the first half of the 20th century.

However, when estimating segregation in rural areas, we find that segregation increased there just as dramatically as it did in urban areas. This finding forces reevaluation of the traditional segregation story—it is not simply due to urbanization or the growth of suburbs, since rural areas featured neither. Rural areas that experienced inflows of black residents experienced rising segregation levels, but so did counties that lost black residents, and counties whose racial compositions remained relatively unchanged. White flight to the suburbs may account for the growth of black urban cores, but it cannot account for similar levels of sorting in rural areas.

How did this happen?  The sweeping rise in both urban and rural segregation across communities in every region implies a significant drop in social interactions between black and white residents. Essentially, black and white people were much less likely to live close to one another by 1940.  Consider a city like Chicago that moved from a moderate level of segregation in 1880 to a high level of segregation in 1940. During this period, the black residents rose from 1.2% to 7.7% of the total city population. Unsurprisingly, only 1% of white households had a black neighbor in 1880. However, despite the nearly seven-fold increase in the black population share, the percentage of white households with a black neighbor declined to only 0.4% in 1940, hence the enormous rise in neighbor-based segregation. The percentage of black residents with a white neighbor declined from 66% in 1880 to only 5% in 1940.

This dramatic decline in opposite-race neighbors could have profound impacts on the evolution of racial biases. Social scientists have theorized that interpersonal contact provides a critical avenue for reducing prejudice between groups. Changing racial attitudes requires interactions between the races. In this respect, the sweeping rise of residential segregation patterns over the 20th century may very well have created an environment that has allowed racial prejudices to harden in the nation overall and lead to the stubbornly persistent racial inequalities we see today.

The article ‘The National Rise in Residential Segregation’ published in The Journal of Economic History won the recent IPUMS USA Published Research Award. Read the full article here.


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