There is always a debate about how good or evil pie charts are. While visualization purists believe pie charts should be avoided at all costs, newbies find creating and using pies very easy and often over do it. I have blogged few techniques involving pie chart visualizations like in-cell pie charts, speedometer charts, donut clocks and the response from readers has been mixed.
My opinion with respect to pie charts is that, when used in moderation they are OK. I say this because of the overwhelming awareness of pie charts. You can go and show it a school kid with the same comfort level as you can to your CEO and both will interpret the message in the same way (that is provided your pie chart is interpretable). Also, pies with 2 or 3 slices tend to be easier to understand.
Yesterday, I saw this very good example of using pie-charts in moderation at CNN’s Where tax burden falls chart (see it on the right)
The chart shows, how tax payers and tax burden is broken up across each of the income ranges. It enables quick analysis of disparities between income, representation % and contribution % in simple, understandable pie chart form.
Also, see how they avoided the trap of making two big pie charts.
despite having the choice putting 2 giant pies (one for tax payer % breakup by bracket, another for how much taxes each bracket paid) these folks avoided that trap and chose to stick to multiple pie charts. If you had combined them in to two pie charts, I am sure it would have been a disaster. (corrected to make it simple to understand :D)
What is your stance on pie charts?