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
2025 8,000,000,000 13
2043 9,000,000,000 18
2083 10,000,000,000 40
source: UN, Dept. of Economic and Social Affairs, Population Division (2011). World Population Prospects: The 2010 Revision.
note: projected populations based on the medium-fertility variant.