In Close Races, Kaiser of Junk Charts writes about the “racetrack” charts used in the New York Times to compare candidates’ performances in different demographic categories. Specifically, the charts compare votes received by Clinton and Obama in cities, suburban regions, and rural areas. The New York Times charts are donut charts, or pie charts with different circumferential bands representing the different demographic regions. A portion of the New York Times chart is shown here:
I got this chart from Kaiser’s post, and he got it from a “recent issue of New York Times magazine”. The problems with this kind of chart have been described in Kaiser’s recent post as well as earlier posts on the Junk Charts blog. The problems stem from the data being depicted as angular measures, when the relative arc length and area of the ring segments varies greatly even for segments with similar angles.
Kaiser proposed an alternative chart, a two-sided bar chart, similar to a population tornado. My version of Kaiser’s chart is shown below. I’ve added vertical gridlines to help compare bars on either side of the midpoint which are near 50%
The appeal of this chart is that it shows a bar as wide as the voting block, skewed to the side of the winning candidate. You can easily imagine a see-saw, where the longer side outweighs the shorter side. In Wisconsin, the bars are fairly evenly balanced, while in Tennessee, they range from strongly Obama-sided to strongly Clinton-sided.
I made a clustered bar chart in an attempt to improve the comparison of Clinton’s vote totals to Obama’s.
This chart is good for showing comparisons in close races, but I felt it only confused the widely varied results from Tennessee, which the two-sided chart showed more elegantly.
This works better than the clustered chart if direct comparisons are needed, although I think the two-sided bar chart is better at showing the leanings of the voting populations.
I’ve followed up with some changes and additions here: Close Races 2.