World's population to reach six billion.

The United Nations (UN) estimates that the world's population will reach six billion on October 12, 1999. The world's population reached one billion in 1804; subsequently, one billion increases came at intervals of 123, 33, 14, 13, and 12 years. Population growth rates increased over time because of high fertility rates and declines in mortality rates, especially since the early to mid-1900s. The UN projects that it will take 14 years for the world's population to reach 7 billion and another 15 years to reach 8 billion.