The racetrack graph

Dec 14, 2005

A reader, Nick, sent in this fantastic example of chartjunk.  It is an absolute classic.  He points out - as have we here - that a simple table works better.

We shall call this genre "
racetrack graphs".  If Italy and Japan both traversed 20 metres in distance, it'd appear as if Italy's curve was longer than Japan's because Italy has the inside track!  This bias is well known to anyone who has run track.

The way this chart is constructed is to have length of curve proportional to angle, not distance (see below left); however, our eyes are naturally drawn to the circumference!  When we see Japan's green line, we perceive the length of the line, not its angle.  In particular, notice that the large separation between Canada and Japan represents a 19% difference, which should be double that between Italy and the vertical line (below right).

Nick has a few other examples at his site.  Well worth a look!

And thanks to Jef (see comments) for pointing out my subtraction error.  I will correct the graphic later. (12/14/05, 10 am)  Graphic corrected. (9 pm)