Wednesday, September 14, 2011

The Pie Chart Challenge

I contend that the pie chart should never be used. I've blogged about this before and I think the main contender for a replacement is the sausage. But there are still doubters :-) (Not everyone agrees)

The main problems with pie charts are:

1. It is difficult for humans to compare areas. So the area of the pie slices is hard to compare.

2. It is difficult for humans to compare angles. So the angle of the pie slices is similarly hard to compare.

3. Humans are much better at comparing lengths.

Amusingly, 1 and 2 above were exploited by Steve Jobs in a presentation:

On Hacker News yesterday I was challenged thusly:
Re: the claim that groups of pie charts are especially awful, I have a counterexample. How would you express this more clearly without a series of pie charts?
The charts in question look like this:

I responded with:

Which I contend is better because: it's easy to make a visual comparison between support across the different parties, and it's easy to see which parties are closest to the 50% majority threshold (or even the 66% super-majority threshold).

And, so, I give you the Pie Chart Challenge. If you truly believe that a pie chart is best then send me the chart (and its underlying data) and I will attempt to recraft it as a different, more descriptive and easier to comprehend, chart of my choosing.

If I fail (i.e. I believe that the sent pie chart is the best way to show the data), then I'll... eat humble pie.


If you enjoyed this blog post, you might enjoy my travel book for people interested in science and technology: The Geek Atlas. Signed copies of The Geek Atlas are available.


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