Wednesday, 4 May 2016

Locating neighborhood diversity in the American metropolis

In recent years, the growing racial and ethnic diversity of American suburbs relative to their central cities has attracted significant attention in the popular media.  This is perhaps best exemplified by writer Alan Ehrenhalt’s suggestion that a “demographic inversion” characterizes many large American cities, in which old models of central city diversity in contrast to suburban homogeneity no longer hold. 
The purpose of my article is to explore this shifting geography of metropolitan diversity in US metropolitan areas, and suggest some methods of exploratory data analysis and visualization to accomplish this.  One such proposed method is a diversity gradient, which I define as a smoothed curve fit through a scatterplot that displays neighborhood-level racial and ethnic diversity scores against neighborhoods’ distances from their respective urban cores.  Diversity scores are represented with a metric called the scaled entropy index, in which a score of 1 represents perfect evenness between non-Hispanic whites, non-Hispanic blacks, Asians, and Hispanics.  An example diversity gradient from the article for Dallas-Fort Worth, Texas is below. 

The visualization suggests greater homogeneity in urban neighborhoods around 5 miles from central Dallas and Fort Worth when compared with neighborhoods 15-20 miles from the downtowns, where the most diverse neighborhoods in the entire metropolitan area tend to be located. 

Additionally, I explore geographic shifts in diversity over time through exploratory spatial data analysis.  I accomplish this through identification of spatial “clusters” of high and low diversity neighborhoods in the Chicago and Dallas-Fort Worth metropolitan areas, and compare the locations of these clusters between 1990 and 2010.  An example for Dallas-Fort Worth is found below. 

As the figures illustrate, high-diversity clusters (represented in red) within 10 miles of either core city hall in 1990 in some cases have given way to low-diversity clustering by 2010, especially on the Dallas side of the metropolitan area.  High-diversity clusters in 2010 tend to be located between 10 and 20 miles from the urban cores, suggesting that neighborhoods of high racial and ethnic diversity are increasingly more commonly found in the suburbs rather than closer-in areas. 

While the article focuses on Chicago and Dallas-Fort Worth, I have developed an interactive application at that allows users to explore aspects of the analysis in the article for themselves for many of the largest metropolitan areas in the United States.   Future research will expand upon the exploratory spatial data analysis component of the article to identify where within metropolitan areas neighborhoods tend to shift from high to low-diversity clusters and vice versa, comparing these shifts among the US’s largest metros. 

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