Every few years, the latest data from the UN’s World Population Prospects is hurriedly plugged into thousands of spreadsheets and models in banks and government finance ministries the world over, as investors and economists set out their plans for the years ahead.
The UN’s numbers are considered the gold standard, but Seattle-based public health research group the Institute of Health Metrics and Evaluation is also a big player. Vienna’s International Institute for Applied Systems Analysis also publishes respected projections every few years.
The methods vary. Some stick to demographic and economic inputs, while others make assumptions about social change. As a result, the outputs also differ. The UN’s latest central estimate forecasts that the global population will peak at 10.3bn in 2084. The IIASA puts the peak at 10.1bn in 2080, and IHME at 9.7bn in 2064.