Range Graded Proportional Circle Map

In reference to Range Graded Proportional Circle Maps, the data is divided into groups and the cartographer chooses circle sizes for adjacent classes so that the map reader can easily distinguish between circle sizes, and therefore, categories. So, each circle size represents a specific range of data on the determined scale. An example of this type of map is shown below:

In the map above, the cartographer chose a series of different sized cirlces to represent specific amounts of data.

http://www.neiu.edu/~jrthomas/377/circle.jpg