Global population growth continuing
The United Nations released new population projections for all countries in July 2014. Gerland et al. analyzed the data and describe the probabilistic population projections for the entire world as well as individual regions and countries (see the Perspective by Smeeding). World population is likely to continue growing for the rest of the century, with at least a 3.5-fold increase in the population of Africa. Furthermore, the ratio of working-age people to older people is almost certain to decline substantially in all countries, not just currently developed ones.
The United Nations (UN) recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, the world population is unlikely to stop growing this century. There is an 80% probability that world population, now 7.2 billion people, will increase to between 9.6 billion and 12.3 billion in 2100. This uncertainty is much smaller than the range from the traditional UN high and low variants. Much of the increase is expected to happen in Africa, in part due to higher fertility rates and a recent slowdown in the pace of fertility decline. Also, the ratio of working-age people to older people is likely to decline substantially in all countries, even those that currently have young populations.
Materials and Methods
References and Notes
Lutz W., Samir K. C., Dimensions of global population projections: What do we know about future population trends and structures? Philos. Trans. R. Soc. London Ser. B 365, 2779–2791 (2010).
United Nations, World Population Prospects: The 2012 Revision (Population Division, Department of Economic and Social Affairs, United Nations, New York, 2013).
UNAIDS, Global Report: UNAIDS Report on the Global AIDS Epidemic 2013 (UNAIDS, Geneva, 2013).
Lee R. D., Tuljapurkar S., Stochastic population forecasts for the United States: Beyond high, medium, and low. J. Am. Stat. Assoc. 89, 1175–1189 (1994).
National Research Council, Beyond Six Billion: Forecasting the World’s Population (National Academy Press, Washington, DC, 2000).
Alkema L., Raftery A. E., Gerland P., Clark S. J., Pelletier F., Buettner T., Heilig G. K., Probabilistic projections of the total fertility rate for all countries. Demography 48, 815–839 (2011).
Raftery A. E., Alkema L., Gerland P., Bayesian population projections for the United Nations. Stat. Sci. 29, 58–68 (2014).
Fosdick B. K., Raftery A. E., Regional probabilistic fertility forecasting by modeling between-country correlations. Demogr. Res. 30, 1011–1034 (2014).
Raftery A. E., Chunn J. L., Gerland P., Sevčíková H., Bayesian probabilistic projections of life expectancy for all countries. Demography 50, 777–801 (2013).
Raftery A. E., Lalic N., Gerland P., Joint probabilistic projection of female and male life expectancy. Demogr. Res. 30, 795–822 (2014).
Oeppen J., Vaupel J. W., Broken limits to life expectancy. Science 296, 1029–1031 (2002).
Wilmoth J. R., Deegan L. J., Lundström H., Horiuchi S., Increase of maximum life-span in Sweden, 1861–1999. Science 289, 2366–2368 (2000).
Raftery A. E., Li N., Ševčíková H., Gerland P., Heilig G. K., Bayesian probabilistic population projections for all countries. Proc. Natl. Acad. Sci. U.S.A. 109, 13915–13921 (2012).
Lutz W., Sanderson W., Scherbov S., The end of world population growth. Nature 412, 543–545 (2001).
Lutz W., Sanderson W., Scherbov S., Doubling of world population unlikely. Nature 387, 803–805 (1997).
Bongaarts J., Casterline J., Fertility transition: Is sub-Saharan Africa different? Popul. Dev. Rev. 38 (suppl. 1), 153–168 (2013).
K. Andreev, V. Kantorová, J. Bongaarts, Demographic Components of Future Population Growth (Technical Paper no. 2013/3, Population Division, Department of Economic and Social Affairs, United Nations, New York, 2013).
United Nations, Population Facts No. 2013/10, December 2013 - Explaining Differences in the Projected Populations Between the 2012 and 2010 Revisions of World Population Prospects: The Role of Fertility in Africa (Population Division, Department of Economic and Social Affairs, United Nations, New York, 2013).
T. A. Moultrie, I. M. Timaeus, “Rethinking African fertility: The state in, and of, the future sub-Saharan African fertility decline,” paper presented at the Annual Meeting of the Population Association of America, Boston, MA, 1 to 3 May 2014; http://paa2014.princeton.edu/abstracts/143218.
Caldwell J. C., Caldwell P., The cultural context of high fertility in sub-Saharan Africa. Popul. Dev. Rev. 13, 409–437 (1987).
Caldwell J. C., Caldwell P., Is the Asian family planning program model suited to Africa? Stud. Fam. Plann. 19, 19–28 (1988).
United Nations, Model-Based Estimates and Projections of Family Planning Indicators: 2013 Revision (Population Division, Department of Economic and Social Affairs, United Nations, New York, 2014).
National Research Council, Aging and the Macroeconomy (National Academy Press, Washington, DC, 2012).
J. Bongaarts, “Demographic trends and implications for development,” paper presented at the International Union for the Scientific Study of Population 2013 Meeting, Busan, Republic of Korea, 26 to 31 August 2013; http://iussp.org/sites/default/files/event_call_for_papers/Session_071_01_Bongaarts.pdf.
Hirschman C., Why fertility changes. Annu. Rev. Sociol. 20, 203–233 (1994).
London Summit on Family Planning, Technical note: Data sources and methodology for developing the 2012 baseline, 2020 objective, impacts and costings (Family Planning Summit Metrics Group, London, 2012).
Peterson H. B., Darmstadt G. L., Bongaarts J., Meeting the unmet need for family planning: Now is the time. Lancet 381, 1696–1699 (2013).
Whelpton P. K., An empirical method of calculating future population. J. Am. Stat. Assoc. 31, 457–473 (1936).
United Nations, in Manual III: Methods for Population Projections by Sex and Age (Manuals on Methods of Estimating Population, Department of Economic and Social Affairs, Population Division, New York, 1956), vol. 25, pp. vii, 81
S. H. Preston, P. Heuveline, M. Guillot, in Demography: Measuring and Modeling Population Processes (Blackwell, Malden, MA, 2001), pp. xiii, 291.
United Nations, World Population Prospects: The 2012 Revision - Online and DVD Edition - Data Sources and Meta Information (POP/DB/WPP/Rev.2012/F0-2) (Population Division, Department of Economic and Social Affairs, New York, 2013).
Gerland P., UN Population division’s methodology in preparing base population for projections: Case study for India. Asian Popul. Stud. 10, 1–30 (2014).
United Nations, in World Population Prospects: The 2012 Revision - Methodology of the United Nations Population Estimates and Projections (Population Division, Department of Economic and Social Affairs, New York, 2014), p. 44.
Ševčíková H., Alkema L., Raftery A. E., bayesTFR: An R package for probabilistic projections of the total fertility rate. J. Stat. Softw. 43, 1–29 (2011).
H. Ševčíková, A. R. Raftery, P. Gerland, “Bayesian probabilistic population projections: do it yourself,” paper presented at the Joint Eurostat/UNECE Work Session on Demographic Projections, Rome, Italy, 29 to 31 October 2013; www.unece.org/fileadmin/DAM/stats/documents/ece/ces/ge.11/2013/WP_13.2.pdf.
H. Ševčíková, A. E. Raftery, bayesLife: Bayesian Projection of Life Expectancy. R Package and documentation version 2.1-1. Original WinBugs code written by J. Chunn (2014); http://cran.r-project.org/web/packages/bayesLife/.
Lee R. D., Carter L. R., Modeling and forecasting U.S. mortality. J. Am. Stat. Assoc. 87, 659–671 (1992).
K. F. Andreev, J. W. Vaupel, “Forecasts of cohort mortality after age 50,” MPIDR Working Paper, Max Planck Institute for Demographic Research, Rostock, Germany, 2006.
Keilman N., How accurate are the United Nations world population projections? Popul. Dev. Rev. 24, 15–41 (1998).
Keilman N., Data quality and accuracy of United Nations population projections, 1950-95. Popul. Stud. 55, 149–164 (2001).
Wheldon M. C., Raftery A. E., Clark S. J., Gerland P., Reconstructing past populations with uncertainty from fragmentary data. J. Am. Stat. Assoc. 108, 96–110 (2013).
M. C. Wheldon, A. E. Raftery, S. J. Clark, P. Gerland, “Bayesian reconstruction of past populations and vital rates by age for developing and developed countries,” paper presented at the Annual Meeting of the Population Association of America, New Orleans, LA, 11 to 13 September 2013; http://paa2013.princeton.edu/papers/130303.
M. C. Wheldon, A. E. Raftery, S. J. Clark, P. Gerland, “Bayesian reconstruction of two-sex populations by age: Estimating sex ratios at birth and sex ratios of mortality,” paper presented at the Annual Meeting of the Population Association of America, Boston, MA, 1 to 3 May 2014; http://paa2014.princeton.edu/papers/140994.
D. J. Sharrow, Y. He, S. J. Clark, A. E. Raftery, “Probabilistic population projections for countries with generalized HIV epidemics,” paper presented at the Annual Meeting of the Population Association of America, Boston, MA, 1 to 3 May 2014; http://paa2014.princeton.edu/papers/141563.
Sharrow D. J., Clark S. J., Raftery A. E., Modeling age-specific mortality for countries with generalized HIV epidemics. PLOS ONE 9, e96447 (2014).
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We thank the entire team involved in the production of the 2012 Revision of the World Population Prospects—in particular, K. Andreev and F. Pelletier. We also thank two anonymous reviewers for helpful comments. This work was supported by NIH grants R01 HD054511 and R01 HD070936. A.E.R.’s research was also supported by a Science Foundation Ireland ETS Walton visitor award, grant reference 11/W.1/I2079. Views expressed in this article are those of the authors and do not necessarily reflect those of NIH or the UN.
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