Source: U.S. Census Bureau, International Data Base, December 2010
Update
Figure 6.9 Yearly growth rate of the human population (1950–2050)
RULE OF 70The Rule of 70 is a useful rule of thumb that roughly explains the time periods
involved in exponential growth at a constant rate. Doubling time is the amount
of time it takes for a given quantity to double in size or value at a constant
growth rate. We can find the doubling time for a population undergoing
exponential growth by using the Rule of 70, where dt represents the change in
time, and r represents the growth rate, which must be entered as a whole number
and not as a decimal (e.g., 2% = 2).
For example, a population with a 2% annual growth rate would have a
doubling time of 35 years.
Key properties of doubling time are: