Doughnuts vs Pie — A Visual Primer
Why a handful of doughnuts are nearly always better than a pie
This is not an opinion piece. My opinion on pie charts and doughnut charts shouldn’t matter to anyone. Too many reports and visualizations are built on opinion and subsequently quite flawed. That is not to say that your opinion or that of your audience is not important. Visualization is an art.
Great visualization is achieved when we enable our audience to gain the maximum amount of insight with the least amount of effort. It is a tool for engagement but also comprehension efficiency. — this author
With that in mind, this short primer lays out several components necessary to achieve great visualization. Against all of these criteria, doughnut charts outperform pie charts.
Clarity
One of the first major differences between a pie chart and a doughnut chart is in how you read them. Pie charts actually offer three separate options. You compare the ratio of the angles, the ratio of the areas of each wedge or slice, or last you can use the length of the outer circumference. The doughnut chart only offers the latter, though it gives you both an inner and outer edge to work with.
As I noted in a prior article, charts are often distorted. Because of this, the complexity of the pie chart is rarely a benefit. A typical audience will contain individuals who prefer each of the three methods. This makes distortion of a pie chart far more common than people realize.
People who prefer the pie over the doughnut often do so because the pie offers more stylization. You can make a pie 3D. You can tilt it. You can explode it. You can fill it with interesting patterns or skins. You can even make it different shapes. But, ALL of these options will distort your graph for at least a portion of your audience.
A doughnut can get distorted, too. It is just much easier to avoid. So long as the edge lengths remain a fixed ratio (no tilted view), the graph should remain true to the data.
Spatial Efficiency
For fans of Edward Tufte, this is a major theme of his writing. Tufte rails more against ‘wasted ink’ then too much white space, but both can be issues. Filling a page with meaningless color creates clutter and slows comprehension. White space that is not purposely used to create focus (think Google/Apple) is equally troubling.
The pie chart suffers from the former. By definition, there is nothing you can do about it. Any effort to limit that extra ink will only leave you with a doughnut chart instead. But the doughnut chart suffers from the latter, so why trade too much ink for too little?
The answer is focus. The white space of a doughnut chart draws the eyes of your audience. So use it! That space is perfect for a total, a lift comparison, or a trend arrow. Honestly, you should be able to cleanly fit all three!
Comparison & Benchmarks
One limitation of both of these chart styles is their ability to show comparisons or benchmarks. Standard bar charts are better for this purpose but have limitations of their own. One note — the doughnut chart IS actually a form of bar chart.
To compensate for this deficiency, I prefer to use these charts in sets. A single pie or doughnut may be all you need when your audience is only looking for a quick visual distribution. But that lone chart will not be able to convey a depth of information that is very actionable or satisfying.
A set or cluster of charts allows the audience to compare and contrast changes. It effectively adds an additional dimension to your graphic. This could be across time, populations, etc. It also allows you to better leverage the legend (needing only one), the color pallet (which will now serve as a connector as well), and (for the doughnut) exploit multiple central focus points to convey a message or call out important information.
Don’t limit your creativity
This article was designed to introduce some components of great visualization and call out some important considerations when deciding between chart types. But returning to our initial call out, visualization is an art. Considerations are not fixed rules. Balance, style, and creativity should also be part of your arsenal. Graph on!
If you liked this article, please recommend it by click on the heart icon ♥ and be sure to subscribe to Charting Ahead and other Corsair’s publications.
For more on this subject consider-
