Work by Thomas Malthus
In 1798, Thomas Malthus wrote:
The power of population is so superior to the power of the earth to produce subsistence for man, that premature death must in some shape or other visit the human race. The vices of mankind are active and able ministers of depopulation. They are the precursors in the great army of destruction, and often finish the dreadful work themselves. But should they fail in this war of extermination, sickly seasons, epidemics, pestilence, and plague advance in terrific array, and sweep off their thousands and tens of thousands. Should success be still incomplete, gigantic inevitable famine stalks in the rear, and with one mighty blow levels the population with the food of the world.—Malthus T.R. 1798. An essay on the principle of population. Chapter VII, p61
Notwithstanding the apocalyptic image conveyed by this particular paragraph, Malthus himself did not subscribe to the notion that mankind was fated for a "catastrophe" due to population overshooting resources. Rather, he believed that population growth was generally restricted by available resources:
The passion between the sexes has appeared in every age to be so nearly the same that it may always be considered, in algebraic language, as a given quantity. The great law of necessity which prevents population from increasing in any country beyond the food which it can either produce or acquire, is a law so open to our view...that we cannot for a moment doubt it. The different modes which nature takes to prevent or repress a redundant population do not appear, indeed, to us so certain and regular, but though we cannot always predict the we may with certainty predict the fact.—Malthus, 1798, Chapter IV.
After World War II, mechanized agriculture produced a dramatic increase in productivity of agriculture and the so-called Green Revolution greatly increased crop yields, expanding the world's food supply while lowering food prices. In response, the growth rate of the world's population accelerated rapidly, resulting in predictions by Paul R. Ehrlich, Simon Hopkins, and many others of an imminent Malthusian catastrophe. However, populations of most developed countries grew slowly enough to be outpaced by gains in productivity.
By the early 21st century, many technologically developed countries had passed through the demographic transition, a complex social development encompassing a drop in total fertility rates in response to lower infant mortality, increased urbanization, and a wider availability of effective birth control, causing the demographic-economic paradox.
On the assumption that the demographic transition is now spreading from the developed countries to less developed countries, the United Nations Population Fund estimates that human population may peak in the late 21st century rather than continue to grow until it has exhausted available resources.
Historians have estimated the total human population back to 10,000 BC. The figure on the right shows the trend of total population from 1800 to 2005, and from there in three projections out to 2100 (low, medium, and high). The second figure shows the annual growth rate over the same period. If population growth were exactly exponential, then the growth rate would be a flat line. The fact that it was increasing from 1920 to 1960 indicates faster-than-exponential growth over this period. However, the growth rate has been decreasing since then, and is projected to continue decreasing. The United Nations population projections out to 2100 (the red, orange, and green lines) show a possible peak in the world's population occurring as early as 2040 in the most optimistic scenario, and by 2075 in the "medium" scenario.
The graph of annual growth rates (above) does not appear exactly as one would expect for long-term exponential growth. For exponential growth it should be a straight line at constant height, whereas in fact the graph from 1800 to 2005 is dominated by an enormous hump that began about 1920, peaked in the mid-1960s, and has been steadily eroding away for the last 40 years. The sharp fluctuation between 1959 and 1960 was due to the combined effects of the Great Leap Forward and a natural disaster in China. Also visible on this graph are the effects of the Great Depression, the two world wars, and possibly also the 1918 flu pandemic.
Though short-term trends, even on the scale of decades or centuries, cannot prove or disprove the existence of mechanisms promoting a Malthusian catastrophe over longer periods, the prosperity of a small fraction of the human population at the beginning of the 21st century, and the debatability of ecological collapse made by Paul R. Ehrlich in the 1960s and 1970s, has led some people, such as economist Julian L. Simon, to question its inevitability.
A 2004 study by a group of prominent economists and ecologists, including Kenneth Arrow and Paul Ehrlich suggests that the central concerns regarding sustainability have shifted from population growth to the consumption/savings ratio, due to shifts in population growth rates since the 1970s. Empirical estimates show that public policy (taxes or the establishment of more complete property rights) can promote more efficient consumption and investment that are sustainable in an ecological sense; that is, given the current (relatively low) population growth rate, the Malthusian catastrophe can be avoided by either a shift in consumer preferences or public policy that induces a similar shift.
However, some contend that the Malthusian catastrophe is not imminent. A 2002 study by the UN Food and Agriculture Organization predicts that world food production will be in excess of the needs of the human population by the year 2030; however, that source also states that hundreds of millions will remain hungry (presumably due to economic realities and political issues).
Ester Boserup wrote in her book The Conditions of Agricultural Growth: The Economics of Agrarian Change under Population Pressure, that population levels determine agricultural methods, rather than agricultural methods determining population (via food supply). A major point of her book is that "necessity is the mother of invention." Julian Simon was one of many economists who challenged the Malthusian catastrophe, citing (1) the existence of new knowledge, and educated people to take advantage of it, and (2) "economic freedom", that is, the ability of the world to increase production when there is a profitable opportunity to do so.
The economist 
Friedrich Engels also criticizes the Malthusian catastrophe because Malthus failed to see that surplus population is connected to surplus wealth, surplus capital, and surplus landed property. Population is large where the overall productive power is large. Engels also states that the calculation that Malthus made with the difference in population and productive power is incorrect because Malthus does not take into consideration a third element, science. Scientific “progress is as unlimited and at least as rapid as that of population”. On the other hand, Joseph Tainter argues that science has diminishing marginal returns and scientific progress is becoming more difficult, harder to achieve and costlier.
- Demographic trap
- The dismal science
- Human overpopulation
- Malthusian trap
- Overshoot (ecology)
- Olduvai theory
- Pledge two or fewer (campaign for smaller families)
- Oxford World's Classics reprint
- Fischer, R. A.; Byerlee, Eric; Edmeades, E. O. "Can Technology Deliver on the Yield Challenge to 2050". Expert Meeting on How to Feed the World (Food and Agriculture Organization of the United Nations): 12.
- Hopkins, Simon (1966). A Systematic Foray into the Future. Barker Books. pp. 513–569.
- "2004 UN Population Projections, 2004." (PDF).
- "Historical Estimates of World Population, U.S. Bureau of the Census, 2006.".
- "International Data Base".
- Simon, Julian L, "More People, Greater Wealth, More Resources, Healthier Environment", Economic Affairs: J. Inst. Econ. Affairs, April 1994.
- Arrow, K., P. Dasgupta, L. Goulder, G. Daily, P. Ehrlich, G. Heal, S. Levin, K. Mäler, S. Schneider, D. Starrett and B. Walker, "Are We Consuming Too Much" Journal of Economic Perspectives, 18(3), 147-172, 2004.
- World agriculture 2030: Global food production will exceed population growth August 20, 2002.
- The Ultimate Resource II: People, Materials, and Environment in http://www.juliansimon.com/writings/Ultimate_Resource/
- Progress and Poverty, Chapter 7, Malthus vs. Facts in http://www.henrygeorge.org/pchp7.htm
- Engels, Friedrich."Outlines of a Critique of Political Economy". Deutsch-Französische Jahrbücher, 1844, pg.1.
- Tainter, Joseph: The Collapse of Complex Societies, Cambridge University Press, Cambridge, UK, 2003.
- Korotayev A., Malkov A., Khaltourina D. Introduction to Social Macrodynamics: Compact Macromodels of the World System Growth. Moscow: URSS, 2006. ISBN 5-484-00414-4
- Korotayev A., Malkov A., Khaltourina D. Introduction to Social Macrodynamics: Secular Cycles and Millennial Trends. Moscow: URSS, 2006. ISBN 5-484-00559-0 See especially Chapter 2 of this book
- Korotayev A. & Khaltourina D. Introduction to Social Macrodynamics: Secular Cycles and Millennial Trends in Africa. Moscow: URSS, 2006. ISBN 5-484-00560-4
- Turchin, P., et al., eds. (2007). History & Mathematics: Historical Dynamics and Development of Complex Societies. Moscow: KomKniga. ISBN 5-484-01002-0
- 2/2 (2011): 1-28CliodynamicsA Trap At The Escape From The Trap? Demographic-Structural Factors of Political Instability in Modern Africa and West Asia. .
- Essay on life of Thomas Malthus
- Malthus' Essay on the Principle of Population
- David Friedman's essay arguing against Malthus' conclusions
- United Nations Population Division World Population Trends homepage