bullshit #dataviz

Donald Trump won because Hillary Clinton failed to get the vote out. At least, that’s the story this heavily retweeted chart seems to tell (click the chart for a larger version). But according to data visualisation expert Alberto Cairo it’s an example of the kind of bullshit #dataviz we need to fight against. In fact, many people have criticised the chart, for a number of reasons, including:

• The y-axis, obviously.[1] The chart suggests Clinton got about half as many votes in 2016 as Obama in 2012, which of course isn’t true. Some have argued that truncating the y-axis is justifiable in this case because otherwise small differences wouldn’t show. However, with a y-axis starting at zero, you can still see what’s going on.
• Why is it showing only the latest three presidential elections? Add data for elections before 2008, and the picture becomes quite different.
• Not all votes have been counted yet. At some point, Nate Cohn of the NYT has predicted that Trump will get 61.2 million votes and Clinton 63.4 million, when all votes are counted. That would also change the picture considerably.

So who created this bullshit #dataviz and why? The earliest version I could find is by Economics Professor D Yanagizawa-Drott.[2] My guess is that he created the chart as a quick-and-dirty attempt to understand what happened on 8 November, never expecting it to go viral, and that he never gave much thought to its execution.[3] While the chart design is problematic, the idea behind it - explore how turnout affected the outcome of the election - makes sense.

Meanwhile, the post-election dataviz deluge highlighted another problem. People post charts without indicating the source of the data they used. To make matters worse, other people will simply copy and post that chart without saying who they got it from. There should be a rule that if you post a chart, you should indicate the data source and who created the chart - or at least where you found it.