
General consensus by data visualization experts is that pie charts are not very useful at all. In the majority of cases they are misleading, for a number of reasons. We are much better at seeing differences in lengths as opposed to areas. 3D pies, different angles, borders and shadows make the situation worse. More slices to the pie make it even more difficult to understand.
Long live Bars.
http://www.perceptualedge.com/articles/08-21-07.pdf
http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=00018S&topic_id=1
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