bivariate choropleth map

A bivariate Choropleth map shows two different sets of variables on the same choropleth map. In this map each color represents two different sets of numbers. For each color there is a smaller set of numbers which is the population of 1997 and a larger set of numbers which is the median value.

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