

The Pie Chart Challenge - jgrahamc
http://blog.jgc.org/2011/09/pie-chart-challenge.html

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jonnathanson
Rule #1 of Presentations is this: know thy audience.

When Steve Jobs used pie charts in his keynotes, he was addressing an audience
of developers, consumers, and loyalists. These were people he needed to keep
impressed, and a great way to impress people is to make the data seem really
BIG and compelling and outsized. (Remember that one presentation with the
graph that expanded its axes and "zoomed out" in real time? That's serious
data showmanship right there).

Pie charts may not be the most accurate way to represent data, but when your
goal is to sell a story, they can do the job nicely. That even nontechnical
consumers are used to seeing them makes them easily digestible, too; in this
sense, pie charts are a form of universally recognizable data language. Pie
may be junk food of a sort, but it's comfort food all the same.

You seem to believe that there is a "best" way to represent data, but therein
lies the assumption that all audiences are largely homogenous. I disagree.
There are certainly universal principles for good presentation design, but
data representation is a tough one. The sophistication and expectations of the
audience play a huge role in how you should speak to that audience.

~~~
tel
I think the more subtle question is what "best" means here. Knowing the
sources jgc has probably been influenced by, it's going to be something like a
measure of _accurate information absorption by the audience_.

If you want to lie, which it's quite unmistakeable that Job's chart intends to
deceive, then accuracy absorption is not you aim. But if you don't want to
lie, I agree with jgc that pie charts are simply inadmissible.

~~~
jonnathanson
_"accurate information absorption by the audience"_

But I'd argue that we can dissect even further -- in this case, into the
process of information absorption. Certainly a crucial part of absorbing
information is paying attention in the first place. Or understanding what
we're seeing. On both of those counts, pie charts do a pretty quick and easy
job for many hypothetical audiences.

Some of the graphs and charts offered up in this article as alternatives to
pie charts would, quite frankly, confuse the heck out of a lot of audiences.
And if your audience doesn't understand what it's seeing, it's not going to
absorb the information. Furthermore, if it has to be _told_ what it's seeing,
then it's already in an unreceptive psychological state.

I would not advocate lying to an audience, or grossly misrepresenting data.
But I certainly would keep two things in mind: 1) the data-sophistication of
my audience, and 2) the attention span of my audience. A pie chart may not be
terribly precise in its representation of data, but it's clearly, quickly, and
almost universally recognized.

Perhaps there's also room for a compromise in any given presentation: a data
overview slide, with simple pie charts and other "30,000-foot" graphs,
followed by a more detailed breakdown of key measurements in more precise
terms. In this case, the first slide captures attention, and the second slide
ensures accurate delivery.

~~~
tel
I'm not going to source this at the moment, but I'm 80% sure I've read studies
that show pie charts increase audience _confidence_ that they understand
material but reduce their _accuracy_.

Pie charts seem simple and easy to understand, which is really the most
dangerous flaw. It's difficult for the human visual system to compare areas
accurately.

------
Chris_Newton
I think some of this debate is slightly missing a key point: tables are for
showing precise data, but graphics are for showing _patterns_. If you're
expecting your viewer to read accurate values off a chart, you're probably
using the wrong tool for the job. If you're trying to use the same chart type
to show different kinds of pattern in the same underlying data, you're
probably having a "when all you have is a hammer, everything looks like a
nail" problem.

I do agree that pie charts are overused and there is often a better
alternative, but do stacked sausage charts really do much better when it comes
to showing differences between roughly similar values? Here's an example:

<http://imgur.com/zGuwg>

Sure, it's obvious which red bars are longest on the left-hand side, because
_they have a common edge_. But in that case, it's not really the length of the
bars that the viewer is comparing, it's the position of the right-hand end,
just like a simple bar chart.

As soon as you stack thing up, so you're trying to compare sections that don't
align at either end such as the green or orange bars here, it is still
difficult to see which ones are longer. Something more drastic, such as
reversing the order of the bars completely, throws off any comparison, as with
the second and fifth lines.

I don't see how a series of sausage charts like this is much better than a
series of pie charts if your goal is to allow your viewer to compare the sizes
of each category across the series. You need to get the key values onto the
same scale to do that effectively, and I would expect a better choice to be
something like a multi-bar chart (with the same zero level for each bar,
either grouping all categories for each point in the series or isolating each
category in a chart of its own) or perhaps some sort of overlapping line chart
if the gradients are interesting.

------
king_magic
I'm not convinced at all. It took much longer for me to dissect the
information in the example bar chart that it did for me to dissect the
information in the example pie chart. The bar chart was confusing; the pie
chart was instantly clear.

Furthermore, I disagree with the author's assertion that it is difficult to
compare areas and angles, and I personally find it more difficult to compare
length. The author provides no references that support his claims - without
some clear research behind it, I simply cannot take his statements as anything
other than opinion.

------
ed209
Not only does it indicate how close I am to completion, but also which
categories I have completed. Additionally its pie shape makes it easier to use
in this setting (where a horizontal chart would be too big)

[http://www.mint.com/blog/wp-
content/uploads/2010/04/trivial-...](http://www.mint.com/blog/wp-
content/uploads/2010/04/trivial-pursuit.jpg)

~~~
OriginalSyn
That's really the same, trivial pursuit pies are merely a progress bar, each
slice is of equal value.

~~~
ed209
I'm pretty sure when Steve Jobs showed his Market Share pie chart at 19% that
was merely a progress bar too ;)

------
albedoa
There are some good arguments both in this thread and in your blog, and both
for and against the two types of charts.

One thing that you would have to make absolutely clear to your audience when
using the "sausage" chart [1] is that the length represents a whole. Pie
charts obviously represent no less and no more than one whole, but that's not
so obvious with a bar.

You handle this well in your examples by marking the end point with "100%",
but I worry that others would not be as diligent in their labeling if these
charts were to take off.

1\. Is there really no better name for that? :D How about calling them snake
charts or something?

~~~
baconner
Well mostly people call them stacked bar charts no?

Anyway to your point about labeling: For bar charts the axis scale labels are
a requirement. If someone doesn't label scales I'd as kindly as possible
suggest that they shouldn't be making charts at all :)

------
wzdd
I'd add that the pie charts you converted in this post are actually the sorts
of pie charts you were okay with in your first blog post, where you said "pie
charts are really only useful when a small number of categories of data are
far, far greater than others" (<http://blog.jgc.org/2009/08/please-dont-use-
pie-charts.html>), with "republicans" being, arguably, an exception.

~~~
jgrahamc
True, but there are three of them and when you put them side by side they are
hard to compare.

------
webwright
The "sausage" (worst. name. ever. :-) ) solve some of the problems, but not
all of them. With enough slices, it's not always clear which is larger than
which. Depending on what the viewer wants/needs, often a humble bar or column
chart would be more effective. The sausage and the pie both do a decent job
with just a few slices (the sausage is definitely an improvement), but both
break down with a lot of slices.

------
sudonim
The bar chart with independents, republicans and democrats makes it seem like
every group is equally large.

Are there as many independents as republicans?

The bias of this method towards smaller groups is no worse than the pie
charts. But it's not better.

~~~
jgrahamc
I was making no claim about showing the relative sizes of those groups. And I
don't believe the three pie chart version was either.

~~~
tel
This does point out the burden of bar charts: are can be unintentionally more
informative than you wanted them to be.

------
duck
I just have to say that the bar chart you show is so small that I can hardly
read the numbers, so based on that I would say the pie chart won. As you
mentioned in your other article, if you can't read it (aka 3d charts) then it
is pretty much useless.

~~~
yummyfajitas
I think that's an artifact of his blog shrinking both charts.

[http://1.bp.blogspot.com/-FgA0y68WIKI/TnCFePEOtYI/AAAAAAAAAz...](http://1.bp.blogspot.com/-FgA0y68WIKI/TnCFePEOtYI/AAAAAAAAAzY/b9ztftxSv8g/s1600/rGvFW.png)

[http://1.bp.blogspot.com/-_3G3MdDBjCA/TnCFUbUBthI/AAAAAAAAAz...](http://1.bp.blogspot.com/-_3G3MdDBjCA/TnCFUbUBthI/AAAAAAAAAzQ/eXay29YncyU/s1600/Support_For_Direct_Popular_Vote.png)

However, I believe this is a counterexample to JGC's challenge:

[http://www.failepicfail.com/epic-fail/1102/mmm-pie-pie-
eaten...](http://www.failepicfail.com/epic-fail/1102/mmm-pie-pie-eaten-win-
epic-fail-1297353955.jpg)

~~~
Terretta
I was looking for this and am not disappointed. I defy JGC to graph that more
clearly.

Meanwhile, while I agree pie charts are poor for comparisons of area of
slices, or of varying sized pies, but believe the average person understands
the slices well as percentages of a whole. As percentages of a whole they are
glancable.

Further, n the "sausage" charts, the for and against are NOT readily
comparable, as they do not start from opposite ends. The "Other" should have
been graphed in the middle, allowing the balance of the two ends to be
understood and comparison of both positions against the other two bars to be
understood.

Charting well is hard.

------
orenmazor
"I do not believe there is a better representation than a pie chart for this:
<http://goo.gl/yQMve>

awesome.

