World population may swell to 11 billion, study says

Flickr, James Cridland


This story by Gabe Spitzer, our Humanosphere collaborator and podcast producer, is published at

The planet could be much more crowded by the end of the century than previously thought, according to a new report by University of Washington researchers.

That contradicts a general consensus that world population growth is likely to stabilize before long. The population has been expected to rise from the current seven billion or so to about nine billion, before leveling off and possibly declining.

But new projections, based on new statistical models, suggest the numbers will not tail off after all. Instead, statistician and sociologist Adrian Raftery said we could hit 11 billion and counting by century’s end.

“I was quite surprised. I was expecting that conventional wisdom would be borne out,” he said. “But it seems once one brought to bear new, more recent data, that actually there was a substantial change.”

That new data suggests reproductive rates aren’t decreasing as quickly as thought – especially in Africa, where the population could quadruple by the year 2100. Overall, the study concluded there is an 80 percent chance the population will fall between 9.6 billion and 12.3 billion.

Science Population World

Graph. (A) 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) UN 2012 population projections by continent. Science 

Raftery said this estimate used much more rigorous methods than the old models, which relied to some extent on opinion. In the past, he explained, experts would interpret the available data to come up with projections, which they would they use to set up the models that made future projections. Now, he said they use something called Bayesian statistics to cut out the middleman.

Raftery noted the ballooning population was a major concern up until the 1990s, when the models started showing growth would taper off.

“It has kind of fallen off the world’s agenda to some extent. And I think these recent results suggest that this may have been premature,” he said, adding that population growth is a key input to problems like climate change, disease and environmental degradation.

The study, done in conjunction with United Nations demographers, is published today in the journal Science.


About Author

Gabe Spitzer

Gabriel Spitzer covers health and science at KPLU, after a year covering youth and education. He joined KPLU after years covering science, health and the environment at WBEZ in Chicago.

  • Ted Wight

    Thomas Malthus was frightened of population explosion three hundred years ago. Hmmmmmmmmmmmmm. If it weren’t for various dictators and Progressives, wealth would be widely distributed, the United States wealth as it is has been, has taken tens of millions of people out of abject poverty. We buy stuff they make and they get the money (ala Wal*Mart, for example) . More people is not bad.

    • VulcanThunder

      I quess you want to pay three times as much for food? Between the increasing population and the increase in wealth in countries like China and India with billions now demanding more and varied food along with the effects of climate change that are already occuring (like in California), that is what you soon will be paying. Also, if you haven’t noticed, the Chinese are buying up major food producers here in the United States. They see what is coming.

  • AwanderingSoul

    We need some form of a pandemic, especially among Muslims, Chinese, Mexicans and Black.

  • Ted

    Or may not.


    Maybe a small life pension for those males who are willing to be neutered The costs might be less in the long run, and in fact there might even be a “long run” to look forward to.

  • Xenobio

    Racist people have the causality backwards. Studies have shown that people voluntarily reduce the number of kids they have when child mortality decreases and quality of life increases. If you think there’s a good chance your kid might die, and that there is VIRTUALLY NOTHING YOU CAN DO ABOUT IT, you are going to have lots of kids because it’s like playing the lottery. On the other hand if you expect that any child of yours will survive and you can pay for them to go to high school, university, etc., you would have fewer kids but spend more money on them. The projections for Africa are still going up because living conditions still suck for a lot of people there.