Geography Reference
In-Depth Information
release. Once again, whatever part of the area that had census tracts
defined was used.
The original analysis of segregation relied upon the dissimilarity in-
dex. Technically, this index is the proportion of a minority (or majority)
group that would need to move to make the distribution of that group
the same over all geographic units. It can vary from 0.0, representing no
segregation at all, to 1.0, representing total segregation. A second mea-
sure of segregation is the isolation index, which is also a useful standard
measure. It describes the average proportion of a group (e.g., African
American or white) living in the neighborhood (e.g., census tract) that is
inhabited by that group. A related measure is the exposure index, which
gives the average proportion of another group (e.g., African American or
white) that lives in the neighborhood (e.g., census tract) that is inhabited
by a member of one or more other groups.
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Thus, the two sets of measures describe different dimensions of seg-
regation. Dissimilarity looks at how evenly spread a group is within a
particular areal unit. It is not at all dependent upon the size or actual
proportion of the group. The isolation and exposure measures are related
to the actual proportion of a group in a set of neighborhoods. Thus, one
would well expect that the actual experience of either isolation or ex-
posure would be highly dependent upon how concentrated the various
groups were in a given city or metropolitan area as well as how many
members of each group lived in the city or metropolitan area.
Growth and Segregation in Chicago and
Fifteen Other U.S. Cities, 1880-1960
Population growth in Chicago during this period - both overall and in
the African American community - is well known. In 1880 Chicago had a
total population of about 503,000, of which 6,395 were African American,
or about 1.3 percent. This number of African Americans represents what
the 1880 census classiied as Negro and mulato, the later term meaning
“of mixed blood.” Through most of the twentieth century until 2000,
the census used a single race classiication that combined mulato with
Negro. In short, just a tiny fraction of Chicago residents were African
American. Figure 2.2 presents a chloropleth map (now sometimes called
