Bivaraite Choropleth map

http://proceedings.esri.com/library/userconf/proc99/proceed/papers/pap171/p171.htm

Bivarate choropleth maps are very complex graphing method of comparing two variables of a geographical relationship. Bivarate maps are commonly used in government statistical maps, and like other choropleth maps are very easy to interpret, but the process to create these maps are very complex. The map above is just showing the population densities of Ohio.