Between the years 1960 and 2007 there was an increase in world population from about 3 billion to about 6.6 billion people. The increase in 47 years was 3.6 billion; in other words the population more than doubled in that time. We are now at over 7.4 billion and continue to have an exponential growth rate.

From the beginnings of the human race, it took until 1804 to reach one billion people. The second billion was added in approximately 123 years (1927), and reached 3 billion in 1959, only 32 years later. Since then we have been adding another billion every 15 years or so.

It is difficult to pinpoint exactly when these numbers were reached--we cannot count the number of living people exactly at any given moment. We rely on figures generated by census counts and knowledge of average birth and death rates. These give a net number of people added per second. The first link below gives a running total of the best estimate of the current population, as well as the number of additional members of the world's population from the second the link is first opened.