Frequently Asked Questions About Population

Global Population in the 21st Century

1. Waggoner, P. E. & Ausubel, J. H. A framework for sustainability science: A renovated IPAT identity. Proc. Natl. Acad. Sci. 99, 7860–7865 (2002).

2. FAOstat database (accessed 2/29/16).

3. Kastner, T. et al. Global changes in diets and the consequences for land requirements for food. PNAS 109, 6868–6872 (2012).

4. Espenshade, T. J. et al. The surprising global variation in replacement fertility. Popul. Res. Policy Rev. 22, 575–583 (2003).

5. National Research Council (2000), Beyond Six Billion: Forecasting the World’s Population. National Academies Press, p. 44.

6. Lutz, W., Butz, W.P., and KC, S. World Population and Human Capital in the Twenty-First Century. Oxford University Press (2014).

7. National Research Council (2000), p. 90.

8. Gates, M. Gates Foundation Annual Letter (2014). “Myth Three: Saving Lives Leads to Overpopulation.”

9. Jain, A. K. & Ross, J. A. Fertility Differences Among Developing Countries: Are They Still Related to Family Planning Program Efforts and Social Settings? Int. Perspect. Sex. Reprod. Health 38, 15–22 (2012).

10. Cohen, Joel E. How Many People Can the Earth Support? New York: W.W. Norton & Company, Inc. (1995). 

11. Franck, S. et al. Harvesting the sun: New estimations of the maximum population of planet Earth. Ecol. Modell. 222, 2019–2026 (2011).
12. Blomqvist, L, et al. Nature Unbound: Decoupling for Conservation. Breakthrough Institute (2015).

13. United Nations Department of Economic and Social Affairs. World Population Prospects: Methodology of the United Nations Population Estimates and Projections. United Nations Econ. Soc. Aff. XXXIII, 1–66 (2015).