Human population growth

Last class before Christmas we worked on human population growth. So I made a graph to understand better the problem and use it to predict future growth and identify factors that affect population growth.  

 

It took 1649 years for the world population to double, going from .25 billion people to .50 billion people. But it took only 200 years to double once again.

It took 75 years to double a second time and 51 a third time.

 

Based on my graph, in few years the population will reach 8 billion and the population of 2004 will double.