Via Twitter, @Stoltzmaniac sent me this chart, from the Economist (link to article):


There is simply too much going on on the right side of the chart. The designer seems not to be able to decide which metric is more important, the cumulative growth rate of vehicles in use from 2005 to 2014, or the vehicles per 1,000 people in 2014. So both set of numbers are placed on the chart, regrettably in close proximity.

In the meantime, the other components of the chart, such as the gridlines and the red line indicating 2005 = 100 are only relevant to the cumulative vehicle growth metric. Perhaps noticing the imbalance, the designer then paints the other data series in rainbow-colored boxes, and prints the label for this data series in a big white box. This decision tilts the chart towards the vehicle per capita metric, as our eyes now cannot help but stare at the white box.


There are really three trends: the growth in population, the growth in vehicles, and the resultant growth in vehicle per capita. They are all be accommodated in a small-multiples setting, as follows:


There are some curious angular trends revealed here. The German population somehow dipped into negative territory around 2007-8 but since then has turned around. Nigeria's vehicle growth declined sharply after 2006 so that the density of vehicles has stabilized.



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