According to a new statistical projection made by the United Nations (UN) and the University of Washington (UW), Seattle, the world population is likely to reach as many as 13 billion individuals by the end of this century (1). This recent analysis uses modern statistical methods instead of experts’ opinions to estimate future birth rates, one of the determining factors in population forecasts.
World population projection through 2100. The shaded area marks all possible population numbers.
Source: Wikimedia Commons
Throughout the early 2000s, most researchers claimed that the world population would reach nine billion people by the middle of the 21st century and then level off. The projection assumed that birth rates in Africa, which are the highest in the world, would decrease as women’s education and access to birth control improved, but, on the contrary, birth rates in most African countries have declined slightly at best (1).
Africa is not the sole cause of new population growth predictions, however. In recent years, the UN recalculated population projections after consulting demography and statistics experts who provide estimates of future fertility and mortality rates. Not all experts agree on the tendency of these numbers, giving these recalculations room for error.
In the most recent projection, the UN joined with statistician Adrian Raftery of UW and his colleagues, who developed statistical equations that describe how the fertility rate is changing across the globe. These equations allow them to calculate a single estimate and determine the probability of different events, such as the end of population growth.
According to Raftery and colleagues, there is a 95 percent chance that the world population will be between nine billion and 13.2 billion people by the end of the 21st century. Much of the growth will be in Africa, whose population is estimated to rise to four billion by 2100, compared to the current number of one billion (1).
The new projection will be used to predict pollution and global warming levels, prepare for epidemics, determine future infrastructure requirements, and forecast global economic trends. According to economist and population researcher David Lam of the University of Michigan, Ann Arbor, however, there is no guarantee that the world population will continue to rise at its current rate. He points out that the current population growth is slower than what was just experienced (1).
These numbers are only projections, however. An event of extreme magnitude, such as an extreme flu outbreak or war, would be necessary to change the current trend.
1: Williams, Sarah C.P. “Experts Be Damned: World Population Will Continue to Rise.” Science. N.p., 18 Sept. 2014. Web. 22 Sept. 2014.