Global population is expected to hit 7 billion later this year, up from 6 billion in 1999. Between now and 2050, an estimated 2.3 billion more people will be added—nearly as many as inhabited the planet as recently as 1950. New estimates from the Population Division of the Department of Economic and Social Affairs of the United Nations also project that the population will reach 10.1 billion in 2100.
These sizable increases represent an unprecedented global demographic upheaval, according to David Bloom, Clarence James Gamble Professor of Economics and Demography at the Harvard School of Public Health, in a review article published July 29, 2011 in Science.
Over the next forty years, nearly all (97%) of the 2.3 billion projected increase will be in the less developed regions, with nearly half (49%) in Africa. By contrast, the populations of more developed countries will remain flat, but will age, with fewer working-age adults to support retirees living on social pensions.