Choropleth maps are a widely used form of thematic mapping in which geographic areas are shaded using graduated colors to represent numeric values. Each area—typically a census unit or administrative ...

John Gerth, of the computer science department at Stanford, sent a link to a powerful illustration, by Latoya Egwuekwe, of the spreading effects of unemployment across the country during this ...

- a map that uses graded differences in shading or color or the placing of symbols inside defined areas on the map in order to indicate the average values of some property or quantity in those areas ...