Will Population Growth End in This Century?

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Robert Engelman and Yeneneh Terefe

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Population

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Having nearly tripled from 2.5 billion people in 1950 to 7.3 billion today, human population will continue growing through 2070, according to two recent demographic projections. 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.

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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

End Notes:

Will Population Growth End in This Century?

¹ Patrick Gerland et al., “World Population Stabilization Unlikely This Century,” Science, 10 October 2014, pp. 234–37; data are available at U.N. Population Division (UNPD) website, at esa.un.org/unpd/ppp; Wolfgang Lutz, William P. Butz, and Samir KC, eds., Executive Summary: World Population & Human Capital in the Twenty-First Century (Vienna and Laxenburg, Austria: Wittgenstein Centre for Demography and Global Human Capital and International Institute for Applied Systems Analysis (IIASA), 2014); data are available at Wittgenstein Centre website, at witt.null2.net/shiny/wittgensteincentredataexplorer.

² Population Reference Bureau (PRB), “Human Population: Population Growth,” at www.prb.org/Publications/Lesson-Plans/HumanPopulation/PopulationGrowth.aspx; UNPD, World Population Prospects: The 2012 Revision, File POP/1-1: “Total Population (Both Sexes Combined) by Major Area, Region and Country, Annually for 1950–2100 (Thousands).” (Growth rate calculations by the authors.)

³ UNPD, op. cit. note 2.

⁴ Gerland et al., op. cit. note 1; Lutz, Butz, and KC, op. cit. note 1.

⁵ John R. Wilmoth, “The U.N.’s Population Projections Are Likely to Be Right” (letter), Wall Street Journal, 27–28 September 2014; Wolfgang Lutz et al., “Population Growth: Peak Probability” (letter), Science, 31 October 2014, p. 562.

⁶ Gerland et al., op. cit. note 1.

⁷ Ibid.

⁸ Lutz, Butz, and KC, op. cit. note 1.

⁹ Ibid.

¹⁰ The Demographic and Health Surveys that shaped the U.N. assumptions about future fertility can be found at www.dhsprogram.com/publications/index.cfm.

¹¹ UNPD, “Total Population (Both Sexes Combined) by Country or Area, 2010–2100 (Thousands),” at esa.un.org/unpd/ppp/Data-Output/UN_PPP2012_output-data.htm.

¹² See, for example, “UNICEF Report: Africa's Population Could Hit 4 Billion by 2100,” National Public Radio, 13 August 2014.

¹³ Lutz, Butz, and KC, op. cit. note 1.

¹⁴ Ibid.

¹⁵ UNPD website, op. cit. note 1; Wittgenstein website, op. cit. note 1.

¹⁶ Ibid.

¹⁷ Ibid.

¹⁸ Ibid.

¹⁹ Ibid.

²⁰ U.S. Census Bureau, “World Population,” at www.census.gov/population/international/data/worldpop/table_population.php; PRB, World Population Data Sheet 2014(Washington, DC: 2014).

²¹ Lutz, Butz, and KC, op. cit. note 1; PRB, op. cit. note 20.

²² UNPD, op. cit. note 2.

²³ Corey J. A. Bradshaw and Barry W. Brook, “Human Population Reduction is Not a Quick Fix for Environmental Problems,”Proceedings of the National Academy of Sciences, 18 November 2014, pp. 16610–15.

²⁴ Ibid.

²⁵ Ibid.

²⁶ Gilda Sedgh, Susheela Singh, and Rubina Hussain, “Intended and Unintended Pregnancies Worldwide in 2012 and Recent Trends,” Studies in Family Planning, vol. 45, no. 3 (2014), pp. 301–14.

Publish Date:

Dec 18, 2014

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