The Next Century’s Big Demographic Mystery

The first modern, comprehensive attempt to predict the human population’s long-term trajectory took place in 1945. The number of people on Earth had more than doubled in the previous century and a half, to more than 2 billion, and experts worried that food production would not be able to keep pace. Frank Notestein, the founding director of the Office of Population Research at Princeton, estimated that about 3.3 billion humans would be on the planet by the year 2000.

He was only about 3 billion off. The global population by the millennium’s end, and has grown by nearly 2 billion more since. Nevertheless, Notestein’s work was foundational. In 1946, he was appointed director of the newly formed United Nations Population Division (UNPD), which continues to make global-population projections today. These forecasts help national leaders anticipate demand for food, water, and energy, as well as plan infrastructure projects and support systems for children and the elderly. They also assist environmental scientists