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Demography

Taking the measure of uncertainty

Nature volume 387, pages 760–761 (1997)Cite this article

Judged on performance, population forecasts (usually published by institutions such as the United Nations or census bureaux) have a mixed record. They are no worse than forecasts by economists, meteorologists and others who have to deal with complex and partially understood systems, but demographers have been understandably concerned about error in their predictions. Part of their response is a new wave of demographic work focused on the forecasting of uncertainty, per se. Such work aims to forecast a range of demographic outcomes along with associated probabilities, rather than one prediction that will almost surely be wrong.

This new approach is illustrated by Lutz, Sanderson and Scherbov (page 803 of this issue1), who present a forecast of world population through the year 2050 and up to 2100. They conclude that the odds of world population doubling by 2050 are less than a third, whereas a doubling of the fraction of the population that is over the age of 60 is essentially a sure thing. Their results stem from a consensus of expert opinion that human fertility will continue to fall everywhere, trailing the decline of mortality by about a half-century. Their result is also noteworthy for its assignment of explicit probabilities to alternative futures.

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  1. Mountain View Research, 2251 Grant Road, Suite A, Los Altos, 94024, California, USA

    Shripad Tuljapurkar

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  1. Shripad Tuljapurkar
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Tuljapurkar, S. Taking the measure of uncertainty. Nature 387, 760–761 (1997). https://doi.org/10.1038/42818

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