Take care with data visualisation!

Data visualisation is trendy and has been for a while. This is almost completely a Good Thing. A good viz really can help people understand things that would otherwise be hard to get, or notice things that would otherwise be easy to miss. I’m also selfishly pleased about it given that my wife works on an information visualisation product and I’m working for an artist who specialises in a powerful variety of infoviz.

The “almost” is because just as with every flavour of the month, people are now rather too quick to jump on the infographic bandwagon, and get praised much too readily for having done so, even if the graphics don’t help us understand anything. A good infographic is either simple or piggybacks on something we can expect to be culturally well understood like a map of the world. I’ve been seeing more and more things turned into infographics without adding value, and occasionally actively harmful ones that confuse the viewer. Here’s an example I just saw blogged:

The basic idea of using liquid containers to show how changes in birth and death rates, out of sync with each other, have caused population growth is kind of nice, though I’m not sure how much it really helps us. Showing the population of each region as a bar in a chart is certainly nice, but tying it to the liquid containers idea gives us this:

I see at least three problems, possibly four:

  • Where are Greenland, the Asian part of Russia, Australia & Oceania? (Admittedly not that many people, but they’ve still been populated for the whole time represented by this video)
  • Are China & India included in Asia? The maps seem to imply so, but if the scale’s constant (also implied but not specified) then they can’t be included in Asia’s bar.
  • This one’s a bit of a stretch, but: do the colours mean anything? A rainbow has an intrinsic ordering, while the continents don’t – seeing the rainbow suggests to me at least that there is something meaningful to the order.

But the thing that’s really bothering me is the size of the vessels. I look at this and immediately read the blue vessel for Asia as “almost full” while the red, orange & green for the Americas & Europe say “plenty of spare capacity”. I don’t think it’s what the makers intend to say, and if it is then they’re wrong in very important ways, but it’s very much the message I get from that image.

So please be careful if you’re making infographics! It’s just as easy to obscure your message and say things you didn’t intend to as it is to educate usefully.

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