The world population more than tripled during the 20th century from about 1.65 billion in 1900 to 5.97 billion in 1999.[14][15][16] It reached the 2 billion mark in 1927, the 3 billion mark in 1960, 4 billion in 1974, and 5 billion in 1987.[17] The overall population of the world is approximately 7.7 billion as of December 2018. Currently, population growth is fastest among low wealth, least developed countries.[18] The UN projects a world population of 9.15 billion in 2050, which is a 32.69% increase from 2010 (6.89 billion).[14]