Range-graded proportional circle map - cartography courses in the U.S.

http://go.owu.edu/~jbkrygie/krygier_html/geog_353/geog_353_lo/geog_353_lo11.html

 

A range-graded proportional circle map is one of two types of proportional circle maps.  The other type uses continuously variable symbols.  This type, as opposed to using a limited amount of symbols, is graded and each symbol represents a certain range.  The latter type is used in this map:  We can see course offerings in cartography, sorted by state (in the U.S.), using six different sizes of circles for the number of courses offered and different levels of shading for relative importance of these courses.  From the map, it is evident that there are more course offerings with a higher level of relative importance in the Northeast than in the rest of the country, although there is a rather high amount of courses with high relative importance in Kansas.  Although there is no date on this map, I would venture to guess that it is a little dated – I wonder if the course offerings have changed much since this map was developed.