The Economist showed changing pre-tax profits among banks from 2007 to 2011 in Bank Profits Head East. They chose to use a pair of donut charts for this. Weaknesses of this approach are the separation of the pairs of values into distinct donuts. This forces the reader to jump from side to side, and ultimately skip the charts and read the values in the labels. The combined chart has leader lines to help steer the reader’s eyes from side to side, but this adds clutter, and the labels push the donuts further apart, making visual comparisons more difficult.
Who you gonna call? Chart Busters!
In Arrow Charts and Other Alternatives to Multiple Pie Charts on the Forbes magazine web site, Naomi Robbins introduced Arrow Charts as a replacement for double pie charts (and double donuts are at least as bad). I wrote a tutorial on my blog that showed How to Make Arrow Charts in Excel. The technique takes a bit of work, but once you’ve made one arrow chart, you can use it as a template for new values.
I took the example from my arrow chart tutorial and swapped in the Economist’s values:
The first thing I learned from this arrow chart, which I missed in the double donut, is that most regions showed little change, but two regions showed major changes: Asia Pacific gained a huge percentage while Western Europe lost a similar amount. This is a great example of the effectiveness of arrow charts.