Wheel of fortune without prizes: the negative report about negativity
This one takes time to make, takes even more time to read

The art of arranging bars

Twitter friend Janie H. asked how I would visualize a hypothetical third column of this chart that contains the change from 2016 to 2017:


This table records the results from a survey question by eMarketer, asking respondents ("marketers") to identify their top 5 technology priorities in the next 12 months.

I suggested the following:


A hype-chasing phenomemon is clearly at play. Internet of Things and wearable technology are so last year. This year, it's all about A.I. Interestingly, something like "Big data" has been able to sustain the hype for another year.

A design decision I made is to encode the magnitude of the change in the bar lengths while encoding the direction of the change in the colors. One can of course follow the more canonical design of placing the negative bars on the left side of the data labels. My decision is a subtle way of imposing the hierarchy - first I care about magnitude, then I care about direction.

Here is a third way:


This design imposes a different hierarchy. Your eyes are drawn to the top/bottom of the chart.

Any of these designs beat the data table by a mile. It's just too much work for the reader to figure out the value of the changes from the table.


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How about a population pyramid? That way lack of symmetry makes it clear which area grew or shrunk.


This is tough for me to absorb instantly. You are saying to the viewer, "Use one horizontal axis if the bars are black and a different one if they are red. "

I tend to think of color changes in this kind of bar chart as categorical variables, so I would use the "cannonical" depiction of flipping negative bars to the left of the vertical axis. Then way I could add another dimension of information, using your example, using color to separate software and hardware. You could still order the bars by absolute value, though it would be less pretty.

Bob Swerdlow

My father was color-blind and would not have been able to distinguish the black bars from the red, so I prefer the 'third way' chart.

However, to make it clearer, add another horizontal axis at the top, going from 0 at the left to 35% at the right and change the one at the bottom to show 0 at the left to -35% at the right. This emphasizes that the axis is overloaded to show all of the bars going right, with the positive ones at the top and the negative ones at the bottom.


I feel like the negative changes should be represented by negative values - positive values with a different colour is unintuitive. You could still order by magnitude of change to preserve that information.

Paul Smith

I find when there's just two data points per category that a slope chart (basically a line or bumps chart) works best. This not only retains the original data but allows you to clearly see which are the risers and fallers, with the degree of change encoded in the angle of the slope.


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