Exponential growth

In 2011, the world's population topped 7 billion people. Since about 1900 the world's population has grown exponentially - the rate of growth has become increasingly rapid. 
By 2000, there were 10 times as many people living as there had been 300 years before in 1700. Not only is population increasing, but the rate of increase is becoming greater. 

Population grew especially quickly during the late 20th century and early 21st centuries. 
Between 2008 and 2009, 220,980 people were added to the world population every day .
Growth is predicted to continue, but the rate is slowing down. Population is likely to rise to 8.92 billion by 2050 and finally a peak a century later in 2150 at 10.8 billion. This should be followed by a more stable period of zero growth, or even natural decrease. 

Exponential growth produces a line that becomes steeper over time, taking the shape of a letter J. 
However, growth rates are slowing down, so the shape of the graph is levelling off to an S curve. 

Birth rate, death rate, natural change

Birth rate is the number of babies born alive per 1,000 people per year.

Death rate is the number of deaths per 1,000 people per year. 

Birth and death rates are expressed per 1,000 so that figures for countries can be compared. Huge nations such as China and India, can be compared with smaller countries such as Singapore. 

Natural change is the difference between birth and death rates in a country.