divMult and percDiff

Hook to illustrate a problem that needs to be solved (perhaps not exchange-rate focused)

Introducing the divMult scale

# first, without logarithmic rescaling

# second, with log10 transformation of y-axis

Percent differences can work too, if an appropriate scale is used

The problem with percent differences (as typically presented) is that they suggest symmetry in confusing ways, and make the large relative changes near 0 and 100 seem small. But, if an appropriate (i.e., logarithmic) scaling is used, familiar percent differences make great axis ticks.