Proportional Circle Map

Like the map below, choropleth maps, proportional circle maps display specific data of a specific area.  This makes this a thematic map as well. However, in proportional circle maps data is displayed in relation to the size of the circles.  The above proportional circle map is showing the total number of families located in the city of Chicago.  When you look at this map, you can easily see which areas of Chicago have the most families and therefore maybe even which areas of the city are the most family friendly.
The map URL is: http://www.neiu.edu/~tpastaj/391/Assignment%20%232/Assignment_%232.html