Will Population Growth End in This Century?

 

Having nearly tripled from 2.5 billion people in 1950 to 7.3 billion today (see Figure 1), human population will continue growing through 2070, according to two recent demographic projections.1 After that, population either will begin to shrink or will continue growing into the next century, depending on which of the two projections more accurately forecasts the future.

Population Figure 1

In the years following World War II, population grew fairly rapidly, with a rate of growth that peaked in the late 1960s at 2.1 percent a year.2 (See Figure 2.) Since then population growth has gradually slowed—although with a larger base each year, the number of people added annually has changed little. Every year sees the addition of about 80 million human beings on the planet, roughly the current population of Germany, Turkey, or Egypt.3

Population Figure 2

The two population projections—one from the United Nations Population Division (UNPD), the other from the International Institute for Applied  Systems Analysis (IIASA)—agree on how population has grown until now.4 But their future scenarios document a breakdown in consensus among demographers about the future. The people-counting social science seems to be entering a new realm in which scientists recognize how much uncertainty the world and its population face in 2014. Unusually for the demographic discipline, experts even went public with their disagreement about the most likely trends in the critically influential area of how many people will live on the planet in the future: letters to the editor of both the Wall Street Journaland Science by key authors of both sets of projections laid out some of the reasoning behind their numbers.5

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