For the human population to remain steady, each woman needs to have at least two children – one to replace herself and one to replace her mate. The actual number works out to be about 2.1 – to allow for accidents and the like.
In this very good presentation by Hans Rosling, he very clearly demonstrates how much of the western world is way below 2 births per woman, in fact many countries hover around 1, and he shows how as countries “modernize” their birth rates drop rapidly.
That means the end of the human race!
With a little bit more thinking (see here), we’re talking about the year 2300 for the population to be less than 1 billion people. And then afterwards where does it end??!!!
Hans Rosling’s web site is here: www.gapminder.org.
Jeremiah Josey's Blog 
http://www.gapminder.org/videos/dont-panic-the-facts-about-population/