How Did We Hit the 7 billion Mark?

The World's population reached 7 billion on October 31, 2011.  Here is a question for all of us : how exactly did we hit the 7 billion mark?  It is hard to imagine that over two centuries ago the global population was 1 billion.  But if you think 7 billion is a lot, you are in for a rude awakening.  According to U.N. forecasts, the world population could hit a peak of 10.1 billion by 2100 before beginning to decline.  Watch NPR's 2-minute short video to learn some facts about our overpopulated planet.  

via NPR