Assuming the Future: Evaluating World Population Projections

Joseph Chamie, Center for Migration Studies

World population, now at 7 billion, is expected to be nearing stabilization at about 10 billion by 2100 according to the United Nations. In addition to fundamental baseline demographic data and methodology, world population projections are the product of assumptions concerning the future paths of fertility, mortality and international migration for countries, areas and territories across the globe. Population projections are usually evaluated on the basis of how close they come to the actual population some years or decades later. This paper, in contrast, evaluates the reasonableness of the assumptions concerning the components of population change. The criteria for this evaluation of future demographic assumptions are: (a) past trends; (b) future outcomes; and (c) policy responses. Such evaluations are essential given the significant and far reaching implications that population projections have for many critical issues facing the planet, including global warming, biodiversity, the environment, energy, and food and water supplies.