Chandoo says we can Group Smaller Slices in Pie Charts to Improve Readability. Such a pie has too many labels to fit into a tight space, so you need to move the labels around and use leader lines to link the labels to their data points.
An extreme example? Judging from what I see around the web, this is not at all unusual. In fact, 12 points isn’t all that many for a lot of pie charts. They could use a readability improvement.
Chandoo’s technique is to convert the chart to a Pie-of-Pie type, which lets you move some slices to a second pie, leaving a bland “Other” wedge in their place. This can be a deceptive chart. Not only don’t two wrongs make a right, the secondary pie is 75% of the diameter and 56% of the area of the main pie, while having an actual value of only 5% of the main pie.
Chandoo cleans up the chart by moving most of the slices to the secondary pie, then shrinking and hiding the secondary pie by formatting its borders and fills to None.
True, this chart has improved readability. But it has left out a lot of data simply because (a) it didn’t fit nicely into the chosen chart type, and (b) the data made the chosen chart type too cluttered.
For those of us with data loss aversion, the above chart is even worse than a pie chart.
At the risk of becoming a caricature of myself, I’m going to answer Chandoo’s question “Can I use an alternative to a pie chart?” My answer, if you couldn’t guess, or couldn’t at least see below this paragraph, is a bar chart.
This chart takes up about the same space as either pie chart. Readability has been improved compared to both of Chandoo’s pie charts. The text in the labels is large enough for my eyes, which are twice as old as Chandoo’s, to see clearly. Also, there’s no risk of the color scheme troubling a colorblind viewer.
The bar chart improves on the original pie chart by clearly showing all of the data. No points are hidden by their small size, and the labels are next to the data points, not hanging by a thread.
The bar chart is better than the “improved” pie chart because it keeps all of the data in view, not bundled into a mysterious “Other” category.