Milestones (when did/will we reach the next Billion)

year (estimate/projected) amount years in between
1804 1,000,000,000 -
1927 2,000,000,000 123
1960 3,000,000,000 33
1974 4,000,000,000 14
1987 5,000,000,000 13
1999 6,000,000,000 12
2012 7,000,000,000 13
2024 8,000,000,000 12
2040 9,000,000,000 16
2062 10,000,000,000 22
UN, Dept. of Economic and Social Affairs, Population Division (2013). World Population Prospects: The 2012 Revision.projected populations based on the medium-fertility variant.