Why We Despise the Pie Chart: 6 Take-Aways

If you had a dollar for every pie chart you have ever seen in a PowerPoint presentation, how rich would you be? Could you spend a weekend in Paris? Purchase a ski lodge in Telluride? Afford to drink Starbucks coffee?

Right. That rich.

Well, it turns out that the pie chart is the least effective of all the graphs. A canard. A bust. Right at the bottom of the graphical food chain.

The white zinfandel of visual information.

In Save the Pies for Dessert, Stephen Few of Perceptual Edge makes the case that there is almost always a better way to express information than with a pie chart. Despite the “part-to-whole relationship” being immediately obvious, there are far too many drawbacks to overlook.

My 6 take-aways from Few's excellent article include:

1. Unless the information being presented is exactly 25%, 50% and 75%, which rarely happens, people have an almost impossible time comparing the magnitudes of each segment. (In fact, even if the information is in perfect quarters, it has to be set at 3, 6 and 9 on the clock or folks misread it.) And, also like clockwork, we tend to underestimate acute angles and overestimate obtuse angles.

2. To repair these deficiencies, we decorate the pie chart with all of the numerical data we are trying to show graphically. Once this is done—and I dare you to compare—the pie chart is busy and cluttered enough that a simple table tends to be much more powerful. In effect, we end up compensating for the deficiencies of the pie chart and lessen its impact even further. Few reminds us that graphs are useful when a picture of the data makes meaningful relationships visible that could not be easily discerned from a table of the same data.

3. By the way, comparing the size of different circles is almost impossible for most of us. So, if one pie chart represents $100M, and there is one larger and one smaller, most of us cannot estimate the relative value of the two unmarked circles. The author shows an example where his students are asked to judge the relationship between two circles (one is 16X the other) and guess everything from 6X to 50X.

4. The better alternative to a pie chart is almost always a bar chart, with data displayed as a percentage. Try it. Graph a “market” with four competitors having 40%, 30%, 20% and 10% share in a pie chart, and with a bar chart showing four bars arrayed against a horizontal axis of “Market Share.” The relationship among the companies is immediately obvious on the bar chart. And, the more complex the data being presented, the stronger the contrast.

5. Thanks to the ease of PowerPoint, after most of us make difficult-to-read pie charts, we then tip them back for depth, throw in soft lights and bevel the edges. They’re beautiful—and almost impossible to interpret.

6. Edward Tufte, the dean of visual information, said, The only worse design than a pie chart is several of them, for then the viewer is asked to compare quantities located in spatial disarray both within and between pies.

So, as Monty Python might say, we blow our nose at you, lowly pie chart. May we, as Stephen Few suggests, save all of our pies for dessert.

Posted by Entrepreneur Generations

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