National Geographic Chartjunk

National Geographic generally has lots of high quality content, with very high production values and attention to detail in layout and design. Keeping that in mind, I noticed this chart, below in the Feb. 2007 issue on page 56:

This, sadly, is an example of what Edward Tufte calls “chartjunk”. It contains extraneous elements that don’t help:

  • The United States label seems quite superfluous.
  • The mileage scales (including a separate scale for Alaska!) are completely useless in the context of this chart.
  • The “Panic! Panic!” red color is unhelpful; the chart could convey its data more clearly with a range of colors to show the data, rather than only values of red.

Yet it is missing the obvious details that would help:

  • There is a color scale, with the midpoint marked numerically, but no indication of the range. The middle of the range is 494 “deaths per year per 100,000 adults 35 years and older”; that is marvelous specificity, but we aren’t told whether “Low” is 490 deaths per year or 4 deaths per year. Is “High” 500 per year, or 2000? Is the scale linear, logarithmic?

Unfortunately, the meta-message is to not trust this chart – to assume the person showing us this chart is trying to influence us by their choice of what tiny bits of data to include (the midpoint only) and the scary coloring. If it had all the data, I’d be wondering things like “why do so many more people die of heart problems in some areas than others?” rather than “I wonder if they data range is so embarrassingly small that the graph creator chose to omit it?”