In class we have spent a lot of time saying how informative log scales are. Here's a perfect illustration from Martin Wolf in the FT.
1. The main story is : An economically dynamic India is Manmohan Singh’s greatest legacy. He drove radical reform of an anti-market policy regime that was strangling growth. Link.
2. "Singh’s most important achievements as a policymaker were made during his years as finance minister from 1991 to 1996. "
2. How do we see that in the data? Notice the log scale allows us to read off the growth rate break from just that time.
4. and here by contrast is the data on a non-log scale: which fools you into thinking it's a post-2000 effect.