Proportional Circle Maps

This is a type of point pattern map. Circles get larger as the density of the variable increases. One can see the actual counties shown in the map on the near right, with the darkest counties being the densest, and the lighter counties being less dense. On the far right, the circles show that the larger the circle, the denser the variable, and vice versa.

http://makingmaps.files.wordpress.com/2007/08/circle-choro1.jpg