Ronald E. Wilson, U.S. Department of Housing and Urban Development

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Geographic Information Systems organize and clarify the patterns of human activities on Earth’s surface and their interaction with each other. GIS data, in the form of maps, can quickly and powerfully convey relationships to policymakers and the public. This department of Cityscape includes maps that convey important housing or community development policy issues or solutions. If you have made such a map and are willing to share it in a future issue of Cityscape, please contact david.e.chase@hud.gov.

It has long been observed that minorities are often concentrated in impoverished areas and lack access to resources such as jobs, educational opportunities, good-quality food, life services, and face other disadvantages. As such, racial and ethnic segregation is an important factor to consider when crafting public policy. A first step in many analyses of segregation is the production of single racial or ethnic group percentage maps that show geographic patterns where one group is predominant and the other is not. At lower levels of geography, such as census block groups or tracts, these percentage maps are less problematic because the size of the unit is small enough and can reveal a concentration of single racial or ethnic groups within a small area. When examining trends across the United States at the city and county level, however, the percentage mapping approach becomes disadvantageous for two primary reasons.