Bivariate Chloropleth Map

Unlike a univariate map a bivariate map displays two variable and uses two table to represent data. These maps can use symbols or colors to represent different data values for a variable. The map below uses both as it uses small circles each filled to a certain density to represent voter turn out by age while the color represent the margin of victory for the two candidates.




http://wpcontent.answers.com/wikipedia/commons/thumb/c/ca/2004US_election_map.svg/280px-2004US_election_map.svg.png