Life of Pie
This is not a story about Richard Parker. This post won’t make you believe in God. In fact, it’s not about that Pi at all.* Nor is about the other kind of pie — Apple, Pumpkin or Shepherd. It’s about showing data, and the venerable pie chart.
Naomi Robbins issued a challenge on her blog Effective Graphs. Can this chart be improved upon?
I assume what’s behind this question is a general distaste among the Data Visualization community (yes, there is one) for Pie Charts. Their inventor, William Playfair has a lot to answer for. Tufte doesn’t like them, saying, “A table is nearly always better than a dumb pie chart.” Stephen Few thinks you should, “save the pies for dessert.” Naomi has an angular argument against pies, “We make angle judgments when we read a pie chart, but we don’t judge angles very well. These judgments are biased.”
Jorge Camoes has a different, more schizophrenic relationship with pie charts, “if you love pie charts and use them all the time you have a serious problem and you should take a data visualization crash course immediately.” But he does feature them a lot in his blog, and has some great examples of how to use them. Jon Peltier doesn’t like them, and lists a set of alternatives and how-to’s to avoid going down a pie route. Cole Nussbaumer is a hater too. Alberto Cairo is more phlegmatic. He doesn’t hate them, he thinks that circular graphics have their place.
Back to this chart. What’s wrong with it? Jess3 generally does great work, and I really don’t think this is that bad. Yes it uses pie charts**, which have perceptual problems, but there are only 3 slices to each pie, and it’s pretty readable.
The biggest problem, for me, is that it shows both data and insight, in that order. Insight is buried here, and that’s the biggest fault. Insight, (the point of what you are trying to say) should never be buried, it must always be highlighted. If you are showing data and insight, insight comes first.
I’m not a pie chart hater. Like everything in life, it’s about moderation. Sometimes there is a place for circular graphics. But, I do like square pie charts. According to Robert Kosara, “the square pie (or waffle) chart strikes a good balance between engaging the reader and not distorting the data.”
The last, most minor change is removing the legend and putting it directly next to the chart. This removes the need to glance back and forth to figure out what the chart is saying. So here it is, my version:
*If you don’t understand the reference, you’ll have to see the movie, or read the book. It’s a great movie, and (I’m told) a great book.
**Strictly speaking, Donut Charts.
- I give up, I am embracing pie charts
- Who Made That Pie Chart?
(The NY Times)
- Excel Charts: Pie Charts
- Our Irresistible Fascination With All Things Circular
- Engaging Readers With Square Pie/ Waffle Charts
- A Fun Pie Chart About Pie Charts
- Death to Pie Charts
Gavin is a founding partner at fassforward consulting group. He blogs about PowerPoint, Presenting, Communication and Message Discipline at makeapowerfulpoint.com. You can follow him on twitter @powerfulpoint.