On October 31, 2011, the world's population reached 7 billion. Demographers project a range of possibilities for future population growth, with the most commonly cited figure being a world population of 9 billion by 2043.
The 9 billion number assumes a dramatic decline in fertility rates across the world, converging to 2.1 children per woman. This is unlikely unless we respond to the 215 million women around the world who want to prevent pregnancy but need contraception. In nations such as Yemen, Afghanistan, and much of sub-Saharan Africa, women continue to have an average of more than 5 children.
Nearly half the world's population-some 3 billion people-is under the age of 25 and entering their childbearing years. Their childbearing choices, and the information and services available to them, will determine whether human numbers climb to anywhere from 8 billion to 11 billion by mid-century.Sources