There seems to have been a resurgence of doom and gloom population predictions in the last couple of months in the media (see here and here for our treatment of these predictions). So, as an antidote, I present for your consideration a new alternative hypothesis: that the world's population will peak and then decline from about 2070. According to the researchers from the International Institute for Applied Systems Analysis who wrote the new book World Population and Human Capital in the 21st Century:
"World population will likely peak at 9.4 billion around 2070 and then decline to around 9 billion by 2100… Alternative scenarios included in the projections range from 7 billion to almost 13 billion by 2100."
The research was very detailed judging by this description:
"The book involved over 550 experts in a series of surveys and expert workshops held on five continents, in order to include the most accurate and up-to-date information on fertility rates, migration, and other demographic variables for each country around the world.
The new projections are the first to structure population projections for all countries by age, sex, and education, rather than just age and sex, as is done by traditional demographic projection tools."
What is particularly interesting is the research's emphasis on education as a "key demographic factor". The projections show that if education (particularly of women) expands rapidly then the population predicted increases more slowly, peaks and then declines before 2100. If education does not expand, then the global population is predicted to continue to grow to 2100 and beyond. Why is education so important? Well according to Wolfgang Lutz, the leader of the research project:
"'As women become more educated,' says Lutz, 'They gain more power over their reproductive decisions and family size, which almost always translates to having fewer children.'"
The research also shows that the current ageing of developed regions of the world will likely continue and grow more pronounced. This means however that the current measures of age are no longer sufficient and will have to change to reflect a larger life expectancy. The findings of the book contradict UN predictions of a global population of 11 billion by 2100 (predictions which were widely reported). World Population and Human Capital in the 21st Century differs from the UN report not only in its treatment of education of women but also in its use of different current data:
"The new IIASA projections differ from recently updated UN projections indicating that world population is likely to reach 11 billion by 2100. For example, in Nigeria, the UN projections show an increase from 160 million people in 2010 to 914 million in 2100. However, this assumes that the fertility rate in the country have recently been stagnant at six children per woman and will only decline slowly. The IIASA data show that fertility rates have already declined to 5.5 and assume a more rapid decline due to the fact that women entering reproductive age are already much better educated than women in higher age groups."
It will be interesting to see if this results in a more accurate prediction…But accurate or not, I wouldn't be surprised if these predictions do not too much traction or attention - you can't push a population control agenda and therefore sell more pills, condoms, or abortion paraphernalia to Africa if people aren't terribly afraid of imminent overpopulation. So I'd imagine that this prediction and this book will sink from sight, just like this prediction from last year.