Once more didactic. Again the graphic from the newspaper Handelsblatt:
Source: Handelsblatt, 2009-04-30, No. 83, p. 1, original copy this time.
Trucks (Straßengüterverkehr), trains (Eisenbahnen), ships (Binnenschifffahrt).
You think: Truck is faster growing than train. Train is only growing little. Ships hardly at all. But that’s not true. You can’t compare developments for values on different levels. Logarithmical helps.
Now you see: Rail is growing faster than truck. 70 percent to 56 percent. Ship even dropped in between. All in all it grew 3 percent.
Logarithmic doesn’t always work. But more often.