Population projected to peak by 2070

Posted: 12 February 2008

Author: John Rowley

The simultaneous growth of population in some regions of the world, and the beginning of a decline in others - especially Eastern Europe - together with rapid ageing of the population in many regions, is the subject of a fascinating new series of graphic projections, which give a fresh insight into future global population trends.

The analysis, carried out by global researchers at IIASA, is based on assumptions about future levels of fertility, mortality and migration, but adds a wealth of recent new empirical evidence.

IIASA World Population Graph
IIASA World Population Graph
It concludes that the probability that the world's population will peak during the present century at about 9 billion has increased slightly since the last projections in 2001. The median projection shows the global population peaking at 9 billion at around 2070 and then slowly declining.

Under the new projections, shown in the graph above, global numbers in 2100 could be as high as 11.1 billion or as low as 6.2 billion. However these extremes are highly unlikely. There is rather more than a 10 per cent chance that the end of century population will be less than today's 6.6 billion, but only a 2 per cent chance that it might double to 13.2 billion.

Regional shifts

This global picture hides some major regional shifts. Lower than expected birth rates in Eastern Europe and in China are being offset by higher population growth rates in Sub-Saharan Africa. Not only has the previous decline in fertility stalled in some important African countries, but deaths from AIDS are also fewer than previously expected, as estimates of the numbers infected with the virus have been corrected downwards.

IIASA Africa Population Graph
IIASA Africa Population Graph
One result is that Africa's population will almost certainly more than double from around 740 million today, to over 1.5 billion - and could reach as much as 3.3 billion by the end of this century (or as little as 1.1 billion if action is taken soon to radically improve the region's health, education and development prospects).

In a sobering comment the report says: "Two factors will in all likelihood keep Africa at the bottom of world development unless some trends change radically in the near future: continued very rapid population growth together with stagnant or declining educational attainment levels (partly as a consequence of rapidly increasing numbers of children), and the additional environmental and agricultural problems likely to be caused by climate change."

Shrinking numbers

IIASA East Europe Population Graph
IIASA East Europe Population Graph
By contrast, says the report, the ageing population in Eastern Europe is shrinking faster and more dramatically than expected, with persistently low levels of fertility and significant out-migration by young people. Because of this the population is likely to be less than half its present size by the end of the century.

In China, the decline in the population is taking longer. There, numbers are expected to go on growing for some decades before an 'almost certain' decline in the longer run. Because the fall in fertility rates has been so sudden (following the one-child policy) there are still an increasing number of people of reproductive age. But as these decline so will the population, levelling out at around 1.5 billion in the 2020s and then going into a lasting decline.

IIASA China etc Population Graph
IIASA China etc Population Graph
The projections are made uncertain by arguments over the exact fertility rate, but taking this into account IIASA believes the population of China will be back down to the year 2000 level during the 2040s and by the end of the century possibly down to half the 2000 level - or some 700,000 million.

At one time, says report, it was assumed that demographic trends around the world would slowly converge as development led to smaller family sizes and a slowing of population growth worldwide. But in recent years there has been an 'outright divergence' between different regions of the world, which could require a major rethink in the light of climate change.

"A world where there is little international co-operation may not necessarily be a world with a high population," it concludes. "It may be a world with rapid population shrinkage in some areas and explosive growth in others."

This article is based on the summary, by Wolfgang Lutz, Warren Sanderson and Sergei Scherbov, of the new world population projections 2007, produced by the International Institute for Applied Systems Analysis (IIASA) and published in the Winter 2007 edition of Options.