Chart Crimes: Multiple Pie Charts Edition

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When it comes to displaying data in an informative way, there are good ways and bad ways to do it. Bad ways obscure our ability to understand what happened. Good ways showcase the most important points. Today’s Chart Crime is the multiple pie chart crime.

Recall that the purpose of a pie chart is to showcase the percentage of a whole. How do individual data points relate to each other? Pie charts are not good at showing relationships over time.

When I saw this chart of Lego colors, the tattered remains of my soul almost left my body.

To quote Anakin Skywalker, “Nooooooooooooooooooo!”

Again, pie charts don’t work well over time. As little circles, your eyes perceive them as discrete units. You can’t mentally carry data from one chart to the next beyond one or two pies.

Here’s a simplified version. Try to keep all three series in your head as you read these four pie charts:

Above, you can see the orange slice of the pie gets bigger and smaller, but the way the chart is laid out, it’s difficult to glean any usable analysis.

What should I have done instead? This:

A stacked bar chart accomplishes the same purpose as a pie chart in that it shows pieces of a whole and how they relate to each other, but it also does this well over time. In the earlier version of this chart, the orange slice grabbed your attention, but you probably didn’t notice as much the blue slice steadily growing. In the stacked bar chart above, that relationship is much more clear.

Any time you are tempted to make more than two pie charts, opt for a stacked bar chart instead. You will make life easier on yourself and make understandings easier on your audience.

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