Visualizing cases of Chlamydia, Gonorrhoea and Acquired Immune Deficiency Syndrome in the US using Data From Project Tycho

Here I have produced a hierarchical treemap using data obtained from the Project Tycho database:

My question is whether or not people believe the re-use of count value for both colour and size mapping is redundant, and if so, why and, what other relevant information could be conveyed using either mapping without confusing the aim of the visualization? Any other constructive criticism is very welcome.

Some more information on my visualization:

Name of Tool: Tableau
Country: United States of America.
Disease: Chlamydia, Gonorrhoea, Acquired Immune Deficiency Syndrome (AIDS).
Year: 1996
Colour Mapping: Count Value (Pale blue - Low count, Dark blue - High count)
(Count Value I refers to the number of people with the disease in question in a particular time period. Due to the way in which the data is reported, it is possible that people will have been counted multiple times if they remain with the condition for an extended period.)
Size Mapping: Count Value
Position: Count value goes from maximum in the top left to minimum in the bottom right
Data Preparation: The 3 disease datasets were compiled into a single .csv file

Hi Joe.

In answer to your first question, I believe it is subjective. Each mapping has its strengths and weaknesses, by mapping the same variable to both size and colour you are benefiting from the advantages of each and minimizing their weakness. That said, it is perhaps a wasted opportunity to show a more complex relationship and you must question why you chose a treemap when a simpler style would work. Perhaps you could find a variable that you think relates and see if it correlates (big squares have similar colouring), perhaps look at count per capita.

It is hard to tell as the monitor I’m using is old but I’m having trouble with your colour scheme, you might want to look into gamma correction or a different scheme