population projection

The prediction of future populations based on the present age-sex structure, and with the present rates of fertility, mortality, and migration. The simplest projections are based on extrapolations of current and past trends, but a set of very differing projections can be calculated, based on a series of differing assumptions—for example, that current rates of increase will be maintained, will increase, or will decrease.

The 1999 UN projections for the year 2050, in billions, were: ‘high’ 10.5, ‘medium’ 8.9, and ‘low’ 7.3 (UNFPA 1999 The State of the World's Population).