Imperfect melting pot – analysis of changes in diversity and segregation of US urban census tracts in the period of 1990-2010

Analyzing racial distribution and its temporal change in American urban areas is an active area of research. Most attention focused on assessing levels of racial segregation at the spatial scale of a metropolitan area. In this paper, we present an analysis of 1990-2010 changes to racial diversity and segregation on a much smaller spatial scale of an urban census tract. To access time-standardized racial information at the tract and at the census block scales we use multiyear compatible high-resolution population grids. Indices of racial diversity and segregation are calculated for over 30,000 tracts pooled from 41 metropolitan areas. Statistical analysis of this dataset reveals that during the 1990-2010 period urban tracts increased their diversity in line with diversity increases of entire metro areas, but unlike metros, they also increased their levels of segregation. We hypothesize that an increased tendency for the residences of people of the same race to spatially aggregate on the tract scale is the result of individuals exercising preferences regarding their neighbors in reaction to the nationwide increase in diversity of the American population. The study also re-derives diversity and segregation indices from the first principles of the information theory, highlights the need to think about the issue of racial diversity/segregation in terms of spatial patterns, and uses one-person-per-dot maps to connect diversity/segregation indices to actual racial patterns.