Population Growth History

Human population growth is the background fact behind almost all of modern history. It took the entire span of human prehistory to reach 1 billion people (1804); the second billion took 123 years (1927); the third billion took 33 years (1960); the fourth 14 years (1974); and the world reached 8 billion in November 2022. The unprecedented acceleration was caused by the Industrial Revolution, agricultural intensification, and especially the decline of infant mortality through public health, sanitation, and vaccination. The demographic transition: historically high birth rates and death rates (population roughly stable); then death rates fall (sanitation, medicine) while birth rates remain high (rapid population growth); then birth rates also fall as prosperity and education improve (stable or declining population). Most wealthy countries are now below replacement fertility (2.1 children per woman); global fertility has fallen from 5.0 in 1960 to 2.3 today; UN projects world population will peak at 10.4 billion around 2080-2100 and then decline. Thomas Malthus (1798, Essay on Population) predicted catastrophic famine as population outstripped food production — the Green Revolution (1960s, Norman Borlaug's high-yield wheat and rice varieties) prevented the Malthusian catastrophe and earned Borlaug the Nobel Peace Prize.