I know, I know, no one likes pie charts, but I can’t ignore them. A pie chart compares proportions but it is of limited use: either the data is too complex and a pie chart can’t handle it, or it is too simple and you should just use a table. So, the first tip should be:
- Do you really need a pie chart?
- Pie charts shouldn’t be compared (comparing market shares in two regions, for example);
- Don’t use the “exploded” option;
- Five is in general the maximum number of slices you can use in a pie chart, but two is better…;
- If there is no other meaningful order, order the slices from maximum to minimum;
- Put “other” in a gray slice;
- Don’t use a legend, just label the slices;
- Use a very small pie chart in a supporting role for a more complex chart;
- Use the appropriate color codes to identify groups of slices;
- Start the first slice at 0º (noon);
I am sure you can come up with some ideas to make a better pie. Please share your receipt in the comments.
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My faovrite pie is actually a 3D pie, with colored regions stacked vertically. It uses a chocolate cookie crust, with a chocolate pudding layer, then a layer of eggnog pudding, and is topped with an unhealthy amount of whipped cream and garnished with bittersweet chocolate shavings. (”Mmmm, pie…” – Homer Simpson)
Pies do not, however, make a good vehicle for information displays. They are ubiquitous, and we are fooled by their familiarity into thinking that they really show something. A pareto (i.e., sorted column chart) is much more effective at showing comparitive proportions of a whole, particularly if the value axis is scaled to 100% of the whole.
Sounds delicious…
Once a product manager told me he thought a 3D pie chart looked more precise (I can prove he told me that!). This just shows how far we are from removing pie charts out of sight.