My love hate relationship with pie charts. And pie.

I’ve talked a bit before about how I think data visualization is an important tool in the promotion of data use (for example, see this post illustrating my limited knowledge but vast appreciation of infographics). My view is that those who might make use of data must first understand it, and that many are more likely to understand data if it is not in huge tables or buried in paragraphs.

But oh the pie chart. Pie charts are so easily done so poorly. And so rarely done well. I feel like I still regularly see horrible (often 3D or greatly cluttered) pie charts. Most program evaluators, like all humans, fall into two camps — those who use and love the pie chart (sometimes naively — I hope I don’t fall into this camp, but fear at times that I do) and those who loath the pie chart. In the blogosphere, Flowing Data provides a good example of pie chart use here, while John Gargani asks whether the pie chart should be retired.

I’m not entirely ready to abandon using pie charts in my own practice, and here’s why. People understand what a pie chart is supposed to be at a glance (particularly when they’re simply) — that the slices are parts of a whole. This is not so immediately obvious with a column chart or the like. While it’s hard to compare the slices in one chart to the slices in another, it is possible to see the relatives size of the slices (especially if organized from largest to smallest and simply labeled. Certainly it is quickly obvious if there are very large or small slices, which is often the heart of the data being conveyed to begin with.

My answer, then, to John Gargani’s question is that we should definitely retire the bad piechart, and get better about making good pie charts. Frankly, the same can be said for almost every other kind of chart as well, in my opinion. And pie, frankly — some is do very good, some not so much (I prefer those with less traditional crusts though, so perhaps I am not the best authority on pie or pie charts).

Here is a pie chart from a recent report (on the 2012 Marylhurst University Alumni Survey):

Setting aside the awkward title language, I hope the message is clear — that responses are quite mixed, with the largest proportion of respondents reporting a weak connection to Marylhurst. It should be easy too, to add the various slices together as desired (i.e. 35% of respondents who are connected or strongly connected). That said, I’d LOVE to find another way to represent this information, given the challenges inherent (not the least of which is exhaustion) with the pie chart. What do you think? Suggestions welcome!

The bottom line for using pie charts as far as I’m concerned: never over-complicate. In other words, keep it simple smarty. Include only the information, text, and color, necessary to illustrate the data involved. The fewer colors, textures, etc., the better. The simpler the message the better. I’m not sure I’ve followed this rule perfectly with the above example of my own — I will likely try working with shades of one color for future pie charts — when pie charts are necessary at all.

What camp do you fall in — do you love or hate them? If you do see value in the pie chart, in what scenarios do you use or appreciate them? Why or how do you think they can be helpful, if at all? Do you know of other resources that might help those of us still attached to the pie chart? What is your favorite pie recipe?

Oh, and as a bonus for making it through this post — here’s another great somewhat related example of the power of simple data visualizations from Flowing Data that I can’t help but include — How simple charts tell a story.

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9 thoughts on “My love hate relationship with pie charts. And pie.

  1. karen anderson

    Pie charts are interesting…..I have my ‘take’ on them, but I try to keep it around 2-5 variables. It just annoys me to no end when there’s like 15 different categories…..

    -Karen

    Reply
  2. Anjie Raber

    Hi Kim,
    I think you bring up a great debate here-should we be using pie charts to visually represent our data?
    I know when I first heard Stephanie Evergreen say no to pie charts I was a bit devastated, but after reading the work of Stephen Few (and Stephanie’s dissertation) I better understood our inability to estimate and compare size within a pie chart.But, like you-I’m not ready to throw the pie chart out either.
    You make an important point “People understand what a pie chart is supposed to be at a glance (particularly when they’re simply) — that the slices are parts of a whole” but I think we need to challenge what simple means.
    I agree-pie charts do help readers see this is one part of the larger picture but I find we often think we are being simple when in fact we aren’t. . Like Karen said (who posted a comment) when you start adding categories it makes it hard to read and takes away that simplicity. But what I liked about the Nathan Yau’s example of good use of pie charts is-all those pie charts show one part of the whole making it really simple instead of posting all the pieces of the pie.
    In your own pie chart example you provide us with 4 different categories. Honestly I didn’t make the connection that you wanted until I read the text. So what if you did what Nathan did in his example and instead compared the two parts: those who felt connected against those who felt the connection was weak, disconnected, or felt no connection (all clumped together). Then you have two comparisons making it simply easier to digest.
    So I guess what I’m saying is- I agree, I don’t think we should throw out the pie chart just yet. But maybe we should use it to compare just two categories. What do you think?
    -Anjie

    Reply
    1. Kim Post author

      I think this — “what if you did what Nathan did in his example and instead compared the two parts: those who felt connected against those who felt the connection was weak, disconnected, or felt no connection (all clumped together). Then you have two comparisons making it simply easier to digest.” — is a great idea!

      I can also see this/these issues applying just as often to column charts and line graphs, yes? Do Stephen and Stephanie speak to those? (I really need to read their full work! Do you know where to find it?).

      I also worry sometimes about the fine line between simple and overly simple (losing important detail, or dumbing things down excessively).

      Reply
      1. Anjie Raber

        Hi Kim-
        Stephen Few speaks to pie charts directly in both of his books-“Now you see it: Simple visualization techniques for quantitative analysis” and Show me the Numbers: Designing Tables and Graphs to Enlighten.” In the latter source he actually says:
        “I don’t use pie charts, and I strongly recommend that you abandon them as well. My reason is simple: Pie charts communicate poorly”-Stephen Few page 60 2004.
        In Stephanie’s Dissertation-Death by Boredom: The role of Visual Processing Theory in Written Evaluation Communication: she says “skip pie charts because they do not support comparisons, and emphasize the most important thing with changes in font size and color,”

        I think you make a great point -oversimplification. When is simple overdone? I think simplicity is a part of it but really it comes down to the message. What are you trying to tell the reader. If your take away point is connection what’s the best way to communicate that. Maybe it is a pie chart, but make sure the message is the focus of the visual representation. I know I continue to struggle with this myself. It’s easy to get bogged down in creating the graph or chart.

      2. Kim Post author

        Thanks for the resources Anjie!! You rock. And for the wise thinking. I’m glad I’m not the only one who struggles with this stuff. And that there is hope for great improvement in my own work.

    1. Kim Post author

      Great timing! I know I recently saw another great post that illustrates the trouble with pie charts recently. I’ll try to find it and link it here. I’m definitely going to need to write a follow up post to this one given what I’m learning in the Infographics and Data Visualization course I’m currently taking.

      Reply
  3. Pingback: Sheila B Robinson on For the Love (or hate) of Pi(e) · AEA365

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