To determine the extent of any segregation based on race or national
origin in the eight studied communities, the ICRC calculated community-specific
segregation indices. These indices of dissimilarity show the relative
proportion of a minority group that would have to move to achieve
an even residential distribution within the community. For example,
the 1990 segregation index for Dubuque is .51 for African Americans.
This means that 51% of the African Americans living in Dubuque
would have to move to different neighborhoods or census tracts
to make Dubuque non segregated.
For a community to have an index of 0 (indicating no segregation),
the minority population percentages for the city as a whole and
each census tract would have to be equal. For example, if 15%
of a city population is African American, then each census tract
would have to have a 15% African American population to achieve
a segregation-free, 0 index.
One of the most commonly-used methods or formulas to determine
the level of segregation within a community, and the one used
by the ICRC, is the index of dissimilarity as described by Douglas
Massey, Professor of Sociology at the University of Pennsylvania,
in his 1995 article, "The Changing Structure of Black-White
Segregation in the U.S.," Social Science Quarterly.
The index is calculated as:
n
I = SUM .5 | (bi/B) - (wi/W)|
i=1
bi = # minority group members in census tract I
wi = # whites in census tract I
B = # minority group members in the community
W = # white sin the community
n = # census tracts
The index can vary from 0 to 1. A score of 0 means that no segregation exists in the community and a score of 1 means that the community is totally segregated.
The ICRC calculated segregation indices for each of the eight communities based on 1960, 1970, and 1990 census data. The ICRC also calculated an expanded index for each community based on 1990 data which includes suburban census tracts outside official city limits. For example, West Des Moines was included in the expanded index for Des Moines and Marion was included in the expanded index for Cedar Rapids.
Segregation Indices
1960 1970 1990 1990E~ Cedar Falls African American .51 .47 .16 N/A Asian American .47 * .19 N/A Latino * .41 .21 N/A Cedar Rapids African American * .63 .47 .50 Asian American * * .36 .34 Latino * .55 .20 .21 Council Bluffs African American .55 .65 .47 .75 Asian American .33 * .47 .36 Latino * .52 .39 .45 Davenport African American .70 .75 .46 .58 Asian American .47 * .42 .42 Latino * .44 .30 .32 Des Moines African American .77 .72 .62 .63 Asian American .44 * .44 .38 Latino * .50 .28 .31 Dubuque African American * .57 .51 N/A Asian American * * .56 N/A Latino * .68 .29 N/A Iowa City African American * * .26 .26 Asian American * * .39 .38 Latino * * .26 .25 Sioux City African American .74 .71 .53 .54 Asian American .55 * .49 .47 Latino * .54 .45 .43 Waterloo African American .76 .80 .66 N/A Asian American .60 * .49 N/A Latino * .53 .29 N/A Waterloo/Cedar Falls African American .90 .94 .82 N/A Asian American .74 * .69 N/A Latino * .94 .36 N/A ~The 1990E index includes the census data from the suburbs surrounding the communities in the study. The suburbs added include: Omaha (Council Bluffs); Sergeant Bluff (Sioux City); Windsor Heights, Clive, Urbandale and West Des Moines (Des Moines); Coralville (Iowa City); Marion and Hiawatha (Cedar Rapids); Bettendorf, Moline, South Moline and Rock Island (Davenport).
Note: 1960 data for Iowa City, Cedar Rapids and Dubuque is unavailable. The 1960 census for Iowa did not include the Latino population. The 1970 census did not include the Asian American population. 1970 data for Iowa City is unavailable.
SEGREGATION INDICES MIDWEST CITIES
1990 Wichita, Kansas African American .67 Asian American .51 Latino .37 Omaha, Nebraska African American .71 Asian American .40 Latino .40 St. Louis, Missouri African American .80 Asian American .44 Latino .29
Note: 1990 Index of Dissimilarity for Midwest Cities as reported by USA Today (November 11, 1991). The USA Today author used data provided by Professor Massey.
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