World population stabilization unlikely this century

Abstract

The United Nations (UN) recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, the world population is unlikely to stop growing this century. There is an 80% probability that world population, now 7.2 billion people, will increase to between 9.6 billion and 12.3 billion in 2100. This uncertainty is much smaller than the range from the traditional UN high and low variants. Much of the increase is expected to happen in Africa, in part due to higher fertility rates and a recent slowdown in the pace of fertility decline. Also, the ratio of working-age people to older people is likely to decline substantially in all countries, even those that currently have young populations.

Figure 1

(a) Top: UN 2012 world population projection (solid red line), with 80% prediction interval (dark shaded area), 95% prediction interval (light shaded area), and the traditional UN high and low variants (dashed blue lines). (b) Bottom: UN 2012 population projections by continent.

Figure 2

UN 2012 Projection of (a) total fertility rate (top) and (b) total population (bottom) for Nigeria (solid red line), with 80% prediction interval (dark shaded area), 95% prediction interval (light shaded area), and traditional UN high and low variants (dashed blue lines).

Figure 3

UN Projections of potential support ratios, equal to the number of people aged 20–64 divided by the number of people aged 65 or over (solid red line), with 80% prediction interval (dark shaded area) and 95% prediction interval (light shaded area).