Bivariate Choropleth Maps

http://www.directionsmag.com/articles/sports-illustrated-from-swimsuits-to-maps-the-making-of-the-si-sports-atlas/123556

This map is called a Bivariate Choropleth map of the United States which shows where many of our Olympic Athletes come from. A Bivariate Choropleth map uses two variables and different shading to show concentration of those variables.