This week I came across two examples of how not to use pie charts. Both came from very smart people. Here are the examples and some simple rules you can remember to avoid similar mistakes.
You want to communicate clearly and powerfully. You know graphics can help. We have multiple options to easily make interesting graphics. But like any powerful tool, used incorrectly, they can do more harm than good.
The fact that each segment is the same shade is the least of its problems.
Is the percentage of respondents in the $75K-$100K segment greater or lesser in 2014?
See how hard you have to work to make the comparisons?
- To compare relative share, you should use bar charts, like this:
- Totango is an Israeli company, and Hebrew is read right to left. But for a US audience, 2014 should be on the right, not left as in the original.
- The data doesn’t support the original conclusion: “There is an increase in compensation in the top ranges.” We don’t know if the top people got big raises in 2014 or if more people who are highly paid participated in 2014.
It is more correct to say “There is greater concentration in the top salaries in 2014 than. 2013”
Here’s another misuse of pie charts.
The designer wanted to show both the split between returning vs. new visitors as well as the split between single and multiple interactions. They cleverly made the Returning pie (lower right hand side) much bigger than the New pie (upper right hand side) to keep the relative proportion consistent with the original pie chart.
What share of visitors were new and interacted multiple times?
Using the same colors to represent very different concepts will tax your mind.
A simpler, more intuitive way to present this information is a Marimeko chart.
Marketing and sales professionals need to be sophisticated communication experts. But you don’t need to slog through Tufte’s book on graphics to convey information more clearly.
Keep in mind the type of graphic to use for different circumstances to avoid the traps that two smart people fell into this week.
An easy rule to remember is only use a single pie chart to compare relative proportion of segments within the pie chart. If you’re tempted to use 2 pie charts, switch to a different graphic type. Bar charts work for most cases. Marimeko charts are good for comparing across 2 dimensions in the same time period.
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