Board of Governors of the Federal Reserve System

Figure 1: Neighborhood income and distance from CBD

Figure 1 is a composite of 4 two-way line graphs overlaid with scatterplots, showing the relationship between tract income and distance to CBD. The lines are estimated by kernel-weighted locally smoothed regression, the scatterplot shows location of individual tracts, colored by income quartile within the MSA. Each of the 4 graphs represents a different metropolitan area: the top left quadrant is Atlanta, top right quadrant is Detroit, bottom left quadrant is Los Angeles, and bottom right quadrant is Washington DC. For all graphs, the vertical axis is census tract median income in thousands of dollars (0 to 250), the horizontal axis is miles to the CBD (0 to 40).

The shape of the regression lines differs across the 4 graphs: Atlanta's estimated relationship is relatively flat, Detroit and Los Angeles have upward sloping functions, and Washington's graph is non-monotonic, with a downward slope from zero to five miles, then inverting and sloping upward to about 20 miles before flattening out. Additionally, the lines show that the four MSAs differ considerably in income levels (DC has the highest average); and steepness of slope (LA's is the steepest, Atlanta's is the flattest). The scatterplots showing the extent of spatial overlap between tracts in the four quartiles; this can be interpreted as the amount of income dispersion within given distance bands. Looking at tracts within 10 miles of the CBD, Atlanta and Washington have tracts from all four income quartiles represented. In Los Angeles, tracts within five miles of the CBD are almost exclusively the lowest two income quartiles, with the top two quartiles first appearing in the 5-10 mile range. Detroit shows the greatest spatial income segregation: most of the poorest tracts are within 10 miles of the CBD, the next two income quartiles span roughly 10-20 miles, and most of the highest income tracts are beyond 20 miles of the CBD. The dispersion of tracts around the estimated regressions indicate the widest range of tract income in Los Angeles, with the lowest dispersion in Detroit.

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Figure 2: Neighborhood racial composition and distance from CBD: Black population

Figure 2 is a composite of 4 two-way line graphs overlaid with scatterplots, showing the relationship between tract black population share and distance to CBD. The lines are estimated by kernel-weighted locally smoothed regression, the scatterplot shows location of individual tracts, colored by income quartile within the MSA. Each of the 4 graphs represents a different metropolitan area: the top left quadrant is Atlanta, top right quadrant is Detroit, bottom left quadrant is Los Angeles, and bottom right quadrant is Washington DC. For all graphs, the vertical axis is census tract percent black (0 to 100%), the horizontal axis is miles to the CBD (0 to 40).

Regression lines show that black population shares decline with distance from the CBD for all four MSAs, but with notably different shapes and slopes. Atlanta has the smoothest downward slope and the most uniform dispersion of tracts along the line; although many of the tracts nearest to the CBD have very high black concentrations, there are majority black tracts at farther distances in the MSA, and there are close-in tracts with very small black populations. The pattern in Washington, DC is somewhat similar to Atlanta, although the curve is shifted downward and to the right, with a lower average black share and the highest concentration tracts located between 5-10 miles from the CBD. Detroit shows an almost bimodal pattern among tracts within 10 miles of the CBD: centrally located tracts have black populations above 70 percent or below 30 percent, with very few tracts in between. Detroit also has the sharpest drop in black population moving away from the CBD. Los Angeles has by far the lowest average black population share (6.5 percent for the MSA), and only two percent of tracts are more than 40 percent black, producing a nearly flat race-distance gradient. In all four MSAs, the lowest income tracts have an above average black population share, and this is most pronounced in Atlanta and Detroit. However, all four MSAs also have low-income tracts with very low black population shares.

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Figure 3: Neighborhood racial composition and distance from CBD: Hispanic population

Figure 3 is a composite of 4 two-way line graphs overlaid with scatterplots, showing the relationship between tract Hispanic population share and distance to CBD. The lines are estimated by kernel-weighted locally smoothed regression, the scatterplot shows location of individual tracts, colored by income quartile within the MSA. Each of the 4 graphs represents a different metropolitan area: the top left quadrant is Atlanta, top right quadrant is Detroit, bottom left quadrant is Los Angeles, and bottom right quadrant is Washington DC. For all graphs, the vertical axis is census tract percent Hispanic (0 to 100%), the horizontal axis is miles to the CBD (0 to 40).

The regression lines show widely differing relationships between Hispanic population shares and distance to CBD across the four MSAs. In Los Angeles, nearly 20 percent of tracts are more than 80 percent Hispanic, while among the other three MSAs, fewer than 10 percent of tracts are above 40 percent Hispanic. Los Angeles has a clearly downward sloping relationship between Hispanic population and distance to CBD. Los Angeles also has the greatest dispersion among tracts at all distances from the CBD: distance is strongly predictive of Hispanic population share, but with high variance. Atlanta and Washington have slightly parabolic graphs, with the greatest concentration Hispanic neighborhoods located between 5 and 15 miles from the CBD. In Detroit the relationship is nearly flat with a small cluster of heavily Hispanic tracts around four miles from the city center. The scatterplot of tracts by income quartile shows that most of the poorest tracts in Los Angeles are heavily Hispanic. In the other three MSAs, some of the poorest tracts are highly Hispanic, but most poor tracts are largely non-Hispanic. Los Angeles also has the greatest economic diversity among highly Hispanic tracts; of the tracts with at least 50 percent Hispanic population, 17 percent are in the top two income quartiles.

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Figure 4: Neighborhood racial composition and distance from CBD: Asian population

Figure 4 is a composite of 4 two-way line graphs overlaid with scatterplots, showing the relationship between tract Asian population share and distance to CBD. The lines are estimated by kernel-weighted locally smoothed regression, the scatterplot shows location of individual tracts, colored by income quartile within the MSA. Each of the 4 graphs represents a different metropolitan area: the top left quadrant is Atlanta, top right quadrant is Detroit, bottom left quadrant is Los Angeles, and bottom right quadrant is Washington DC. For all graphs, the vertical axis is census tract percent Asian (0 to 80%), the horizontal axis is miles to the CBD (0 to 40).

The regression lines show mostly flat relationships between Asian population shares and distance to the CBD. Tracts in Atlanta and Detroit are, on average, less than 10 percent Asian, with very few tracts above 15 percent. Most of these tracts are in the highest two income quartiles and located 20-30 miles from the CBD. Washington has more tracts that are at least 15 percent Asian, and they are also mostly affluent and suburban, but there are some poor tracts with relatively high Asian concentrations. In Los Angeles, Asian-dominated tracts are drawn from all four income quartiles and appear at varying distances from the CBD.

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Figure 5: Racial/ethnic concentration by distance to CBD

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