Why You Shouldn't Trust Pyramid Charts

Pyramid charts look a lot more attractive than bar graphs, which presumably explains why Office's charting option includes so many of them. However, their visual appeal shouldn't blind you to the fact that they often misrepresent data.

The Stubborn Mule blog dismantles a recent infographic used to discuss whether US food policy indirectly results in America's chronic obesity problem. As the site points out, the use of the pyramid format produces an inaccurate picture of the actual information:

The problem is that the data is represented by the height of each segment of the pyramid, but we tend to perceive the apparent volume of each layer. As a result, the layers near the top appear much smaller that they should relative to the lower layers.

Indeed, the blog makes the case that when it comes to charting, less is definitely more and those :

I would argue that everything below “2-D Column” [in Excel]should be banned from the arsenal of the thinking chart-user. These variants on three-dimensional graphics all represent the trap “chart junk”: fancy extra details that, at best, add nothing to the information being conveyed and, at worst, result in distortion.

I don't doubt some people choose fancy charts for exactly that reason — visual distortion is a neat trick to conceal data you don't want your boss to see. It's still dishonest, however, and if your aim is to be accurate, it's definitely time to rethink those chart types.

Check the whole post for more discussion of which chart types best suit different types of data, and tell us your own favourite charting techniques in the comments.

Pyramid Perversion – More Junk Charts [Stubborn Mule]


Comments

    Glad you liked the post Angus!

    Another example of Excel providing too many tools to the unwary. Same applies to those tilted 3D column charts - the ones that look like a bunch of city buildings - where it is impossible to judge relative heights.

    The origin of the number of charts in Excel stemmed from the Office Suite battles in the 90s when Microsoft Office were competing with Lotus SmartSuite and Novell/Corel WordPerfect Office. In that timeframe, each software developer competed by adding new features to each product and a particularly visual way to advertise new spreadsheet features were to add new charts (because it's difficult to market new formulas as exciting in advertising). That's where we've end up with the large number of chart gallery options that we do today.

    The problem is that once this has been added in a previous version, it's difficult to depreciate this feature in future versions because it introduces incompatibilities with opening files developed on older versions that use these features.

    I have a few charting rules that serve me well.

    1 - Simple as possible - No 3d, no gimmicks, no shading, no gridlines, no backgrounds etc, anything which does not contribute to understanding the message interferes with it. Look at charts in Fortune 500 annual reports, they're minimalist, and for good reason.

    2 - Only one, unambiguous, message - decide what you want your chart to show, and design it to show exactly that, do not use charts which tell multiple stories, do not leave it open to interpretation. If you have doubts about people seeing what you want them to see. Write a description of what you want them to see under the chart, 90% of your audience will accept it without question.

    3 - Use muted, emotionally neutral colours. Default MS Office chart schemes (that yellow, blue maroon, grey combo)look lazy, too bright colours look amateurish. Use a colour wheel to select complimentary colours.

    With a bit of effort Office can produce exceptionally good charting, but only with some effort.

    "Visual distortion is a neat trick to conceal data you don’t want your boss to see."

    but then again...

    "Never ascribe to malice that which can be explained by incompetence."

    I think the vast majority of poor chart selection is by people who (a) don't know any better, and (b) have some fancy graphics engine, or even just Excel, at their disposal, and they use as many of the formatting features as they can. If a little is good, more must be better, and Microsoft would not have included it if it weren't good.

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