In 1800, the planet had a little less than one billion inhabitants between 1800 and 1925, the population doubled, due notably to advances in medicine and sanitation over the course of this period (decrease of infant mortality and increase of life expectancy). The world population then increased from 4 billion in 1975 to 6 billion in 1999 then to 6.6 billion in 2008 [see debate].
Sustainable slowdown ?
Population growth reached its highest level in the 1990s with the increase of 82 million individuals per year. The numbers report an annual growth of 70 million in 2007 (Lester R. Brown, Plan B). The average number of children passed from 6 per woman in 1960 to about 3 today. It could reach two children per woman in the coming decades, just at the level of population renewal. According to the predictions of the United Nations, the world population will reach about 9 billion by the year 2050 then will stabilize.