What's wrong with the Pie?

If there is anything worse than Pie Chart, it would be Pie Chart in 3D. There is no other chart that is so overused and misunderstood at the same time. They are often used to visualize data that would be much better served with different types of charts. But yet, there is no dashboard without a pie chart - unfortunately. They are easy to produce, look friendly, and smart. But don't be fooled and think twice before reaching for a pie!

See this short example? Can you say quickly what the relation between regions is? Can you point out (without looking at numbers in legend) which one has the largest cut? In fact, all three largest slices represent the same value and total share. However, due to perspective and human difficulties in comparing nonlinear shapes, it is hard to spot that at a glance. This can lead to misinterpretation and loss of confidence in your argument. 

only thing worse than a 3D pie chart is more than one of them

So, if you really have to use a pie chart follow simple rules:

1. Sort and organize your data - people tend to read pie charts clockwise, put the largest slices in the beginning - from 12 o’clock.
2. Use with nominal variables.
3. Always make sure that numbers add to 100%.
4. Avoid comparing the Pie Chart to another.
5. Use six categories or fewer.
6. Keep it simple - do not use 3D or exploded pie charts.

So, do you still want to have a pie?

The purpose of the chart is to enable easy comparison of all data and draw conclusions. While Pie Charts hardly meet those criteria I would recommend using an alternative chart type to depict the date, the rule of thumb with Pie Charts is simpler they appear, the more meaningful they become.