That is pretty interesting, but maybe a little misleading, too.
For instance, it's easy to double in size when you go from 1 -> 2. It's a little harder to double in size from 500,000 -> 1,000,000.
Also, a growth rate doesn't show much. Christianity grew mighty fast when Crusaders were running around putting non-Christians to the torch. Join or die is a pretty effective motto.
SpaceAce