I referenced exponential growth at Womenary Class the other day.  Here is what that is:
According to Chris Martenson, one of the things Americans do not understand about numbers is a concept called “exponential growth.”
Many things in the world seem to be following a pattern of this kind of growth.  Take the US national debt:

 
 
 
 
notice the slow growth at the beginning and the steep curve at the end?  That is indicative of exponential growth… it is similar to a double-ing effect.
Look at the growth of the world population:

 
 
 
 
 
The magical and potentially terrifying thing about exponential growth is the way all of the growth and chance happens suddenly and at the end (whatever that it).
Here is the most clear way that I have ever heard it explained:
Imagine I made Fenway Park watertight and then took an eye dropper and placed one drop of water out on the pitcher’s mound.  The water doubles in quantity, starting with that one drop, each minute.
How long would it take to fill the park?
What is your guess?  Weeks, days?  A day, 12 hours?
The answer is 49 minutes.  At 12:49 it is full.  That is impressive, but the bigger lesson is in this question:
At what point was the Park only 10% full?
Answer:  12:44.
Notice that all of the serious stuff happens at the very end!
What else is growing like this?