Why Tufte is Flat-Out Wrong about Pie Charts

Some critics have come crashing down hard on pie charts. Edward Tufte says “the only thing worse than a pie chart is several of them.” Stephen Few says “save the pies for dessert“. Cole Nussbaumer says “Death to pie charts.”

Well, they are all wrong. Pie charts deserve your respect. And I’ll tell you why.

First, let’s consider the critics’ valid criticisms:

1. A bar chart allows more accurate comparison than slices in a pie chart

This is true. But not every chart is about making precise comparisons. Sometimes you only need approximate values so you can engage in a discussion. It’s not necessary to see that one slice is 1% larger than another slice to have that discussion.

For instance, take this pie chart from Stephen Few’s article. Clearly, a bar chart gives more precise comparisons.

But what if, instead, the only point you want to make is that the 2 largest distributors control 65% of the market. Which graph demonstrates that more clearly?

 

Few admits there is research (Spence and Stephan Lewandowky, 1991) demonstrating pie charts are superior in this case, but he assumes this is a very “rare in the real world”. On the contrary – this is extremely common in business presentations where the goal is to tee up issues for discussion, not just lay out the data for detailed study and comparison.

In fact, if you sort your pie slices from largest to smallest, you don’t need to depend on visual comparisons. The ordering tells you which is larger, right?

 

2. A line chart shows trends more clearly than side by side pie charts

Again, this is often true. But it depends on the data you have, as well as the impact you want on the audience. Certainly a pie chart with 10 slices is difficult to compare over time. But what about a pie with just 2 slices?

Tufte’s dogma often unravels when you press on it just a little. He argues you cannot accurately see trends when you compare pie charts side by side. In fact, pie charts CAN be a better way to visualize side by side data when the data is simple. And when you’re comparing percentages, bars are NOT more accurate than pie charts. Look at these two displays. Which one communicates more quickly?

 

In this case, a pie chart is not hard to compare. But what about a line graph? Certainly, it does the job. But there’s also a bit of confusion. Because we are referring to 3 separate events and how they differ. A line graph communicates a smooth continuation of changes throughout the day. That isn’t quite what we are saying and so it takes a bit of mental gymnastics for the reader to adjust the line graph to its intended meaning. The criss-crossing lines also introduce a bix of complexity.

 

In fact, despite some of the valid reasons to avoid pie charts, there are also valid reasons pie charts can be SUPERIOR to line charts and bar charts:

 

1. Puts the audience in a positive frame of mind

Perhaps most importantly, the visual system LIKES round things more than sharp angles. Research finds our emotions are more positive to rounded corners than sharp corners. No matter how accurate your data, you cannot deny bar charts are just BORING to look at. Or, at least, more boring than pie charts.

 

Some in the hard-core scientific community do not recognize emotion as a valid reason to use pie charts. That’s understandable given their mission of presenting data truthfully and accurately.

But great presenters have a different mission: to simplify ideas and motivate audiences. And they know that precise logic and measurements are not enough; you also have to appeal to them emotionally. Pie charts help put the audience in a positive frame of mind.

 

2. Communicates part-to-whole relationship better

At a glance, you know a pie chart is splitting a population into parts.

Bar charts do not have the same meaning. You can signal to the reader the bars add up to 100%, by adding a column or an annotation. But this requires some extra mental gymnastics by the reader to understand the bar chart represents 100%. Nothing beats a pie chart for instantly communicating 100%.

 

3. Easier to estimate percentages

Research shows that it’s easier to estimate the percentage value of a pie chart compared to a bar chart. That’s because pies have an invisible scale with 25%, 50%, 75% and 100% built in at four points of the circle. And the angle of the pie’s interior corner provides an additional cue not available in unlabeled bar charts.

Especially as pie charts become smaller, and you need to use a lot of them, pie charts can communicate percentages much more quickly than bar graphs. See for yourself. (here’s another example)

Tufte is wrong to make an assertion about pie charts based on his own context (the analysis and presentation of complex data) and use broad strokes to apply that to domains where he has no expertise (presenting and selling ideas in the boardroom). Pie charts have earned their place in your business presentations.

So, take some advice from someone who presents data to executives. Use pie charts

  1. When you want to affect your audience emotionally
  2. When you want to quickly communicate a part-to-whole relationship
  3. When approximate values are enough to have a productive discussion

And my advice to Tufte? Pick up a copy of my new book, tentatively titled “Storytelling with Graphs” for a more balanced and practical view of the role of graphs in visual communication. I’m hoping to have it released this summer.

About the author: Bruce Gabrielle is author of Speaking PowerPoint: the New Language of Business, showing a 12-step method for creating clearer and more persuasive PowerPoint slides for boardroom presentations. Subscribe to this blog or join my LinkedIn group to get new posts sent to your inbox.

 

The Greatest Storyteller of All Time Is ________

I’m blessed to live in Kirkland, Washington where I attend church where the minister is Judah Smith, author of Jesus Is ___, one of the top-selling Christian books on Amazon.

And I was reminded this week by Judah’s sermon that the greatest storyteller of our time is not Steve Jobs, not Martin Luther King, not any TED talker. It is Jesus Christ. And the story told in Luke 15 is a great example of the power of storytelling.

The story goes that the High Priests were bothered that Jesus was hanging out with the worst kinds of people; having lunch with drug dealers, pimps, prostitutes, murderers, rapists, thieves. The priests demanded that Jesus explain why he was spending time with these worthless people.

Jesus does not respond with a logical explanation. Instead, he responds with three stories.

 

“A shepherd had a flock of 100 sheep and he counted them everyday. One day he counted only 99. So he left his flock in search of the lost sheep. And when he finally found it, he celebrated.”

“A woman had 10 silver coins. One day, she only counted nine. She tore her house apart, throwing couch cushions and emptying out dresser drawers in search of it. And when she finally found it, she celebrated.”

“A man had two sons. The youngest son said ‘father, give me my college money and all my inheritance.’ Then he moved to Amsterdam and spent all the money partying. One day, all the money was gone. The friends were gone too. The boy had no home, nothing to eat. He ended up working for a farmer, feeding the pigs.

Eventually, the boy decided to swallow his pride and return home, to beg for forgiveness. He knew he had disgraced his family, but perhaps his father would give him a job as a hired hand. When he returned home, his father saw him across the yard. He flung open the door and ran to his son, his robes flapping in the wind. He reached the boy and embraced him and the boy began sobbing and begging for forgiveness. But the father just ignored him, kissed his dirty face and ordered his hired hands to bring the boy a clean robe, sandals and to prepare a feast to celebrate his return.

The oldest son was naturally miffed. ‘You’ve never thrown a party for me. But my brother, who has blown all your money, who has disgraced us, gets a feast! Why would you do that?’

The father replied ‘Try to understand. You have always been with me and everything I have is yours. But your brother was dead, and he’s alive again. He was lost, and now is found.'”

 

So why does Jesus spend extra time talking to sinners? His answer can be found in these three stories. I will not interpret them for you. The power of storytelling is that you, the listener, arrives at the answer on your own.

About the author: Bruce Gabrielle is author of Speaking PowerPoint: the New Language of Business, showing a 12-step method for creating clearer and more persuasive PowerPoint slides for boardroom presentations. Subscribe to this blog or join my LinkedIn group to get new posts sent to your inbox.