The United Nations Probabilistic Population Projections: An Introduction to Demographic Forecasting with Uncertainty

The United Nations publishes projections of populations around the world and breaks these down by age and sex. Traditionally, they are produced with standard demographic methods based on assumptions about future fertility rates, survival probabilities, and migration counts. Such projections, however, were not accompanied by formal statements of uncertainty expressed in probabilistic terms. In July 2014 the UN for the first time issued official probabilistic population projections for all countries to 2100. These projections quantify uncertainty associated with future fertility and mortality trends worldwide. This review article summarizes the probabilistic population projection methods and presents forecasts for population growth over the rest of this century. Copyright International Institute of Forecasters, 2015