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World Population Milestones

Find a list of world population milestones, from when the total world's population reached 1 billion in 1804 to 7 billion in 2011.

1 billion in 1804
2 billion in 1927(123 years later)
3 billion in 1960(33 years later)
4 billion in 1974(14 years later)
5 billion in 1987(13 years later)
6 billion in 1999(12 years later)
7 billion in 2011(12 years later)

Source: United Nations Population Division
Population StatisticsTotal Population of the World by Decade, 1950–2050