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| It took from | to reach |
| Neolithic Age to birth of Christ (10,000 years) | 300 million |
| Birth of Christ to 1650 (1650 years) | 500 million |
| 1650 to 1850 (200 years) | 1 billion |
| 1850 to 1925 (75 years) | 2 billion |
| 1925 to 1962 (37 years) | 3 billion |
| 1962 to 1975 (13 years) | 4 billion |
| 1975 to 1987 (12 years) | 5 billion |
| 1987 to 1999 (12 years) | 6 billion |
| 1999 to 2007 (8 years) | 6.6 billion |