New Study: World Population Set to Hit 11 Billion By the Year 2100

A study published today in the online edition of the journal Science predicts that the world’s population will continue to grow steadily throughout the 21st century, contradicting the widely-held belief that world population was getting close to leveling off.

The study, a joint project between the University of Washington and the United Nations, was the first to employ modern Bayesian statistics. This more complex statistical method combines all available information to make a more accurate prediction.

Traditional projections only take into account life expectancy and fertility rates, producing estimates with more error (ie. a wider range of population projections). This study, however, utilized significantly more governmental data, including things like mortality rates and migration trends.

“Earlier projections were strictly based on scenarios, so there was no uncertainty. This work provides a more statistically driven assessment that allows us to quantify the predictions, and offer a confidence interval that could be useful in planning,”

said Patrick Gerland, a demographer for the U.N. that was one of the authors of the study.

Using these methods, the researchers determined that the world population in 2100 will be closer to 11 billion, nearly 2 billion more than widely-cited estimates from previous studies.

Total world population projected to 2100. Dotted lines are the range or error using the traditional projection method, while shaded regions are the uncertainties using the new statistical methods. The darker shading is the 80 percent confidence intervals, and the lighter shading shows the 95 percent confidence intervals. (Credit: A. Raftery / UW)

Total world population projected to 2100. Dotted lines are the range or error using the traditional projection method, while shaded regions are the uncertainties using the new statistical methods. The darker shading show the 80 percent confidence interval, and the lighter shading shows the 95 percent confidence interval. (Credit: A. Raftery / UW)

Adrian Raftery, a professor of statistics and sociology at the University of Washington, was one of the lead authors of the study:

“The consensus over the past 20 years or so was that world population, which is currently around 7 billion, would go up to 9 billion and level off or probably decline,”

he said, adding,

“We found there’s a 70 percent probability the world population will not stabilize this century. Population, which had sort of fallen off the world’s agenda, remains a very important issue.”

 

The study, which used the most recent U.N. population data from July, showed that the majority of this century’s population growth will be taking place in Africa. The main reason for this high projection is that birth rates in Sub-Saharan Africa haven’t been falling quite as fast as had been expected.

The study predicts that Africa’s population will nearly quadruple this century, with an 80% chance the continent will have a population between 3.5 billion and 5.1 billion by the year 2100.

Population predictions by continent. The darker shading show the 80 percent confidence interval, and the lighter shading shows the 95 percent confidence interval. (Credit: A. Raftery / UW)

Asia’s population, which is at about 4.4 billion right now, is predicted to peak at 5 billion around the year 2050 and then begin to steadily decline.

The rest of the world will experience fairly minimal changes in population with Europe, North America and Latin America all experiencing relatively modest growth.

Read more from Science Daily here.

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