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At present the world's population is growing quickly, though this has not always been the case.

• Until the 1800s the world's population grew slowly for thousands of years.
• In 1820 the world's population reached one billion.
• In the early 1970s, the world's population reached three billion.
• By 1999, less than 30 years later, the population had doubled to six billion.
• The global rate of population growth is now one billion every 15 years.

The graph shows this pattern of accelerating growth (including the predicted population for 2025).