In the 1980s and 1990s, researchers came to understand poor urban neighborhoods as blighted, depopulated areas, based on important ethnographic observations in a handful of cities. This image helped inform influential theories of social isolation and de‐institutionalization. However, few scholars have examined whether those observations were representative of poor neighborhoods nationwide—and whether they are representative today. Based on a descriptive analysis of the largest 100 U.S. metropolitan areas using normalized census tract boundaries, we document an important transformation in the conditions of poor neighborhoods. We find that the depopulation in poor neighborhoods often reported in cities such as Chicago and Baltimore was, in fact, typical across cities in 1990. Today, it is not. Moreover, heterogeneity across cities has increased: The experience of neighborhood poverty is likely to depend more today than in 1990 on the city in question. In fact, the most typically studied cities, such as Chicago, Baltimore, Philadelphia, and Milwaukee, are increasingly atypical in this respect. Addressing today's core questions about neighborhood effects, how and why they matter, requires paying far greater attention to heterogeneity, conducting more ethnographic observation in ostensibly unconventional cities, and addressing the historically extreme conditions in a newly unique subset of cities.


Influential research on the negative effects of living in a disadvantaged neighborhood assumes that its residents are socially isolated from nonpoor or “mainstream” neighborhoods, but the extent and nature of such isolation remain in question. We develop a test of neighborhood isolation that improves on static measures derived from commonly used census reports by leveraging fine-grained dynamic data on the everyday movement of residents in America’s 50 largest cities. We analyze 650 million geocoded Twitter messages to estimate the home locations and travel patterns of almost 400,000 residents over 18 mo. We find surprisingly high consistency across neighborhoods of different race and income characteristics in the average travel distance (radius) and number of neighborhoods traveled to (spread) in the metropolitan region; however, we uncover notable differences in the composition of the neighborhoods visited. Residents of primarily black and Hispanic neighborhoods—whether poor or not—are far less exposed to either nonpoor or white middle-class neighborhoods than residents of primarily white neighborhoods. These large racial differences are notable given recent declines in segregation and the increasing diversity of American cities. We also find that white poor neighborhoods are substantially isolated from nonpoor white neighborhoods. The results suggest that even though residents of disadvantaged neighborhoods travel far and wide, their relative isolation and segregation persist.