Monday, July 13, 2015

The stickiness of visualization conventions

Visualization conventions are as sticky as any other kind of convention. But stickiness isn't a proxy for goodness. We shouldn't use a graphic form uncritically just because it has become the default to represent a specific kind of data. Tradition alone isn't a good textbook.

At the bottom of this post there's a before-and-after exercise*. The original, on the left, comes from Spain's Just for the record, I have mindlessly done tons of parliament charts like that in the past. The “mindlessly” part of that sentence is critical, as I was mimicking what many news infographics designers were doing.

But one day I actually tried to read the parliament-looking chart, and make comparisons. I couldn't. I needed to read every single figure to be able to mentally visualize variations.

You can see the evidence yourself. Read just one or two figures in the first chart below, force yourself not to read the rest, and then try to estimate changes accurately. Good luck with that.

So the parliament chart is nearly useless; a table would've been better. This chart is more a nice-looking abstract illustration than a visualization because a visualization should be an aid to understanding, not a hurdle.

*NOTE: I made a slope chart, but I'd be fine with a bar chart, a dot plot or even a divided bar chart (suggestion inspired by Clement Levallois)