The great Pi Day pie chart debate

GX founders Abe Gong and James Campbell go head to head on whether pie charts are useful

Erin Kapp
March 13, 2023
Erin Kapp
March 13, 2023
Two people hold pieces of a pie chart

Great Expectations is a company full of data practitioners, so naturally, we have some strong feelings about our chosen tools, methodologies, and visualization approaches. So on Pi Day, an annual opportunity to celebrate nerd culture, we asked our leaders to join us for a debate: Are pie charts good?

In the affirmative was James Campbell, cofounder and CTO. He brought statistics, the nostalgic tale of giving directions in a more analog age, and a surprisingly effusive dismissal of DataViz luminary Edward Tufte. In the negative was Abe Gong, cofounder and CEO, who pointed out how pie charts enable data crimes, an argument bolstered by the Twitterverse.

The affirmative: pie charts are simple and that’s a good thing

Right off the bat, James conceded that pie charts have their flaws. However, his central argument was that pie charts are so intuitively easy to read that they have become part of our visual language. He argued:

  • Pie charts appeal to our natural sense of wholeness and are great at telling “the story of the whole,” provided that story doesn’t comprise more than 4 or 5 parts.

  • Everyone knows how to read a pie chart, so they’re easy to consume, unintimidating, and don’t require a legend.

  • Known problems with pie charts, in particular the wont for interpreters to misestimate relative proportions, can easily be fixed with easy-to-interpret markers.

James said pie charts’ simplicity is a feature, not a bug. He used the analogy of giving someone directions in an age before GPS. You would only give the information you thought they needed: Go down this road for three miles and turn right here. If you come to this landmark, you’ve gone too far. Compare that with modern phone maps, which have layers of information about every street and everything on them.

“Pie charts are for giving directions. Imagine the simple map that only has the roads you need; it's just the distilled information that's relevant for you,” he said.

The negative: there is always a better way

Abe said anyone using pie charts shows a lack of imagination.

“There's basically never a time where you can't make your case better with something else. So every time I see a pie chart, I see settling.”

He echoed pie chart haters the world over, saying:

  • Viewers are famously bad at interpreting pie charts, so they often mislead—sometimes mistakenly, sometimes deliberately.

  • Bar charts convey the same information without the risk of misinterpretation and in less screen real estate.

It turns out Twitter agrees—even if the question was a little less than scientific.

On this, we agree: Pi Day is awesome

Despite their differences, our founders were in 100% agreement (which would be depicted as a space-hugging circle if it was illustrated as a pie chart) that Pi Day is a wonderful celebration of nerd culture.

Abe said: “It celebrates math! I think (we could use) more of that rationality in our society; I think it's a good thing and I have lots of good memories of Pi Day parties with friends.”

James answered by reciting Pi to 10 decimal places.

“Pi Day is fun because it is a celebration of nerdiness and the geek subculture that likes to learn more about the world. Also, because you get to eat a lot of pie, and who doesn't love pie?” James said.

What do you think? Join the discussion on Twitter.

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