Proportional circle map

http://geographyfieldwork.com/DataPresentationMappingTechniques.htm
A proportional circle map displays its data by solely using circles as symbols. The bigger the circle, the more of that variable; inversely, the smaller the circle, the less of that variable/factor. Basically, the amount of data being studied depends on the sizes of the circles on the map.
The proportional circle map shown above represents the voting registry for the Czech Republic.