Range Graded Proportional Circle Map

http://www.google.com/imgres?imgurl=http://www.geog.ucsb.edu/~jeff/gis/proportional_symbols_files/map1.jpg&imgrefurl=http://www.geog.ucsb.edu/~jeff/gis/proportional_symbols.html&h=509&w=396&sz=84&tbnid=hRwwhBLHD16pAM:&tbnh=131&tbnw=102&prev=/images%3Fq%3Dproportional%2Bcircle%2Bmaps&zoom=1&q=proportional+circle+maps&usg=__3p4c22ApAUilEk6Q_6lGqqw9kqE=&sa=X&ei=6YXvTIydKMWqlAfWmdGgDQ&ved=0CCAQ9QEwAw
This is an example of range graded proportional circle map of internet usage in Europe in 2004.  It is a proportional circle map because the circle sizes are proportional to the the data being showing; it is range graded because only a certain number of circle sizes are used.