Standardized choropleth map - Gini index in U.S. counties

http://www.incontext.indiana.edu/2014/mar-apr/article1.asp

 

This map is standardized or areally averaged.  It uses the Gini index, a measure of statistical dispersion, to sort counties in the U.S. by income.  From this map, you can see that over this five-year estimate, the South and coastal areas in the U.S. seem to have the highest Gini indices, meaning that there is high equality in income in these areas.