John Kastellec points me to this blog by Ezra Klein criticizing the following graph from a recent Republican Party report:
Klein (following Alexander Hart) slams the graph for not going all the way to zero on the y-axis, thus making the projected change seem bigger than it really is.
I agree with Klein and Hart that, if you’re gonna do a bar chart, you want the bars to go down to 0. On the other hand, a projected change from 19% to 23% is actually pretty big, and I don’t see the point of using a graphical display that hides it.
The solution: Ditch the bar graph entirely and replace it by a lineplot, in particular, a time series with year-by-year data. The time series would have several advantages:
1. Data are placed in context. You’d see every year, instead of discrete averages, and you’d get to see the changes in the context of year-to-year variation.
2. With the time series, you can use whatever y-axis works with the data. No need to go to zero.
P.S. I like the double-zeroes on the y-axis. How better to convey precision than to write “17.00%”? I assume this is just the default software option; I don’t see that anyone would write “17.00%” on purpose.
P.P.S. If you want to see a really ugly graph from that report, check out this one from page 12:
P.P.P.S. Feel free to link in comments to ugly graphs made by Democrats. I’m sure there are a lot of those too!
P.P.P.P.S. John found this lineplot of the data (from Kevin Drum) which indeed shows much more context, in no more space, than the yucky bar graphs.