How Many Computer Scientists Does It Take to Screw Up a Pie Chart?

You can add  silly 3D effects to a pie chart, you can explode all the slices, you can compare multiple pie charts, you can use a legend instead of labeling the slices directly. This will probably render your graph useless, and make you look kind of dumb, but it is not the end of the world-as-we-know-it. But when making a pie chart there is something that you should never ever do, a capital sin that will make you burn in the hell of information visualization: using more than one variable in a single graph.

Well, since we are witnessing the end of the world-as-we-know-it, computer scientists at the University of Utah decided to give a little push, visualization-wise. They are designing a computer application “they hope eventually will allow news reporters and citizens to easily, interactively and visually

[analyze] election results, political opinion polls or other surveys”. They boldly state that they “have developed new techniques for exposing complex relationships that are not obvious by usual methods of statistical analysis” (press release). And what are those new techniques? A doughnut chart:

The outer ring labels the series and the inner ring displays the data. Apparently you may add as many series as you wish and you can filter the results by socio-demographic characteristics.

This is the kind of joke that I would expect to be related to April Fool’s Day, but they seem to be serious about it. No one told them that showing part-of-a-whole is one of the few strenghts of circular charts, that when people see 52,7% they see a pie cut in half, not a quarter, that “whole” mean 100%, not 200% or 300%.

Regular readers know that I rarely utter such harsh comments on visualization ideas and applications (I even tried to create a dashboard using Crystal Xcelsius), but this is the stupidest idea of the year. They should know better (here are some tips).

By the way, I found this through a post by Sarah Perez at ReadWriteWeb. She writes: “unfortunately, the poll-analysis software isn’t quite ready for prime time. What a tease!” Fortunately, it is not! And judging from other posts, they could use an information visualization consultant.

Well, perhaps I’m missing something. Am I?

8 thoughts on “How Many Computer Scientists Does It Take to Screw Up a Pie Chart?”

  1. I don’t think you’ve missed anything. You’re the charting expert who is most tolerant of attempts to use pie charts, so I know you gave this approach more thought than it deserved.

    As soon as the chart deviated from one pie = 100%, they distanced themselves from any valid (if misguided) use of pie charts.

    BTW, after watching the everpresent graphic of pie charts in the left margin of, I’ve decided that pie charts are an effective way to show two percentages that add to 100%, if they meet at 12:00, or even three percentages if the two larger ones meet at 12:00, the third percentage is small, and it is located between the other meeting place of the two larger percentages.

  2. Great chart – I sent this blog to all my team members so they can learn something new. Maybe I can further improve their idea using at least 3 time-series in one pie chart. Personally, I’m missing some cool 3D effects and default excel colors. We all should join a vote this chart for the best idea of the century.

  3. One item you didn’t touch on is the fact that the data on the inner pie is completely impossible to compare. The red side should have the darker red items start at the top. then it would only be 98% bad instead of 100%! 🙂

    Ate Mais

  4. Jon, one of these days I’ll try to put that “tolerance” towards pie charts in context. Regarding this example, I felt almost insulted by the “exposing complex relationships” thing when all they have to offer is a grossly wrong doughnut.

    Tomas, great ideas, thanks for sharing. I believe they’ll contact you shortly to help them with the SDC 2.0 (Stupid Doughnut Chart).

    Jayson, I believe you mean “196% bad instead of 200%!” 🙂

  5. The Economist newspaper likes the semi-circular graph when looking at different parties in a legislature or election. If they had flipped these so these were two semi-pies perhaps with one above the other and the diameter at the bottom you might be able to make some comparisons, but the current view is unintelligible. The Can’t Rate in Blue should be “Can’t Read” with this background.

  6. It’s like hearing someone from the 1930’s complain that today’s cars are really stupid cause they try to run on something other than steam…

    This isn’t a pie chart, if you were too busy trying to sound smart to notice something as basic.

  7. Perhaps it’s not an “official” pie chart, but that’s beside the point. Jorge was pointing out an example of someone starting with something bad (a pie chart) and making it worse.

  8. Blue: you are right, this isn’t a pie chart. In fact, this isn’t a chart at all. This is a stupid idea, and just because it uses new tools doesn’t make it less stupid. But hey, it’s a free country, and if you think that something that goes against basic human perception laws can help you, feel free to use it!

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