Dot distribution map

Dot distribution maps are maps that are used to record the occurrence of a particular phenomenon. They mark the spot of the occurrence by using a varying distribution of dots depending on the frequency of the event. They can be used to determine the relative frequency of unique phenomenon in a particular area, or can be used for tasks as simple as recording the income distribution of a city or state. This map uses dot distribution to show the frequency of AIDS cases in the U.S.

Link: http://cdepart.blogspot.com/2011/02/dot-distribution-map.html