World Population Milestones

Source: United Nations Population Division

* 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)