Range graded proportional circle map

http://www.google.com.pe/imgres?imgurl=http://www.nature.com/nature/journal/v451/n7181/images/nature06536-f2.2.jpg&imgrefurl=http://mikehaleysmaps.blogspot.com/&usg=__FIxmTJwSe8At6D8dSTQU6bQ8R8s=&h=428&w=800&sz=254&hl=es&start=4&zoom=1&um=1&itbs=1&tbnid=FNwhs12ezNClIM:&tbnh=77&tbnw=143&prev=/images%3Fq%3DRange%2Bgraded%2Bproportional%2Bcircle%2Bmap%26um%3D1%26hl%3Des%26ndsp%3D20%26tbs%3Disch:1

This is a range graded proportional circle map that illustrates the number of EID events in the world. We can see that most events occur in Europe and in the United States.