Range Graded Proportional Circle Map

http://www.e-cartouche.ch/content_reg/cartouche/cartdesign/en/html/ThemMaps_ThemData.html

Range graded proportional circle map are very similar to Continuously variable proportional circle map except that these types of maps use a set number of circles and have a range of values for each circle size within the legend. For example, if the number of Irish Catholics were being measured in an area of Boston, MA, there would be a specific number range used within the legend (i.e. 5,000-4,000, 500-400, 50-40, etc). The map above measures the inhabitants of the Communes in Zurich, Switzerland. The legend includes four different sized circles each representing a different number range.