Since he wanted to do this using ArcGIS (something I'm pretty comfortable with), I replied to the list with my suggested method. I suspect crime analysts who lurk on the IACA list are somewhat shocked when a person in executive management responds with a solution to a technical GIS issue. I'm probably older than most of their fathers, too, but from time to time I like to remind myself that I can still do things like create pivot tables, hammer out a little html code, and wrangle a GIS project to make it do what I want it to do.
At any rate, this is similar to what he was trying to accomplish. It is a map of robberies in Lincoln from 2009 through 2013, depicted as five pies, one for each of the Lincoln Police Department's command areas. The differing size of the pies reflects the relative number of robberies within each Team, while two slices of each pie are business robberies and non-business robberies.
It's a simple graphic that at a glance conveys information about both volume and proportion. As you can see, the Southwest Team has a much larger volume of robberies, and the non-business slice is way bigger than most of the other teams. Basically, street robberies are the issue in the Southwest and Center Teams, while business robberies (though still fewer than non-business) are more prevalent in the Northwest, Northeast, and Southeast teams.
|Click image to enlarge|