This interactive visual tool explores how racial homogeneity changes with distance from large U.S. city centers.

After 2040 hits, people of color will overtake whites as the majority population in the U.S. That dramatic demographic shift is taking place in and around metro regions, and to varying degrees. Which neighborhoods are diversifying? And where are they located within each metro? A new paper published online in Urban Studies introduces a fresh, visual framework for answering these questions.  

In it, author Kyle Walker, an assistant professor of geography and director of the Center for Urban Studies at Texas Christian University, suggests tracking changes in neighborhood-level entropy (a measure of how evenly distributed the four major ethnic and racial groups—whites, Hispanics, blacks, and Asians—are within a Census tract) in relation to distance from the urban core. Walker calls the resulting graph a “diversity gradient.” Here’s how he describes the concept in his paper:    

I define the diversity gradient, which is a graphical representation of the localised relationship between distance and neighbourhood racial diversity in a given metropolitan area. The term ‘diversity gradient’ is used in the ecology literature in reference to latitudinal variation in species biodiversity, in which higher diversity is found in the tropics relative to the poles. In regards to urban demographics, this formulation borrows from the idea of the density gradient, which traces how population density within a metropolitan region varies with distance from the urban core.

Walker’s framework lives on the internet as this interactive app. For over 30 large metro areas in the country, this tool charts neighborhood-level demographic data per Walker’s methodology. Here’s the gradient for the Dallas Fort-Worth metro area, which is an emerging immigrant hub, for example:

(Kyle Walker)

Each dot on this graph represents a Census tract. On the vertical axis is its “diversity score,” or entropy index. A “1” on this scale means that the neighborhood has roughly equal shares of the four main racial and ethnic groups mentioned above; a “0” means that that Census tract is homogenous. The graph above shows that the super-diverse areas in the Dallas-Fort Worth metro are around 15 miles from the city center.

What’s really neat about Walker’s app is that selecting dots on the gradient highlights them (in yellow) on the Census tract map on the bottom left side of the browser. Selecting one tract from that map (in blue) pulls up details about it in the window on the bottom right side:

(Kyle Walker)

The tool also lets users compare the change in diversity gradients over time. In Dallas-Fort Worth, suburban diversity leapt up dramatically between 1990 and 2010:

(Kyle Walker)

On the other hand, this is what the diversity gradient for Chicago, a traditional immigrant hub, looks like in the app:

(Kyle Walker)

Notice the incredibly homogenous dots within the first five miles: those are the incredibly racially segregated neighborhoods on the South and West Sides. Pilsen and Evanston, on the other hand, are pretty diverse.

(Kyle Walker)

Of course, every city has a unique history and pattern of demographic change. But here’s Walker’s broad conclusion, from the paper:

These analyses reveal how growing diversity in the suburbs has been accompanied by persistent homogeneity of neighbourhoods in urban cores, and present a framework for future detailed analysis and exploration of neighbourhood diversity in metropolitan areas.

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