Problems are made to be solved – but did you ever manage to get the tooth paste back into the tube again?


Thomas Malthus, an 18th Century English classical economist, died in 1834, but his soul goes marching on. Some see him as a false prophet (The Economist, May 15, 2008), while others claim that “the world’s growing population poses a Malthusian dilemma” (Scientific American, October 2, 2009). In a resolution against the Paris COP21, the climate-sceptic Schiller Institute argues: “The present push for a CO2 reduction program is deeply rooted in … Malthusian ideological motivation. But Malthus was wrong in the Eighteenth Century, and his followers are wrong today.”

Back in 1798 Malthus argued that “Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio. A slight acquaintance with numbers will shew the immensity of the first power in comparison of the second.” (An Essay on the Principle of Population, p.4). His fears were motivated to no small degree by the French Revolution and the misery that had triggered it: “If political discontents were blended with the cries of hunger, and a revolution were to take place by the instrumentality of a mob clamouring for want of food, the consequences would be unceasing change and unceasing carnage, the bloody career of which nothing but the establishment of some complete despotism could arrest.” (p. 418).

By modern standards the supply of data available to Reverend Malthus was poor. We do know, however, that in 1800 world population was less than one billion, and the populations of England and Wales combined failed to match that of London today. Despite the massive population increase since then, the “iron law of wages” has not depressed the incomes of the ordinary employee to the level of subsistence. In fact, in terms of real income the average Englishman of 2015 would probably be the envy of many a duke or baron of 1798. So yes, in retrospect Thomas Malthus was spectacularly wrong[1].

But what about the future of our children and grand-children? Could Malthus still be proven right in the end? The fact that Malthus’ fears have proven unwarranted so far does not prove that they will remain so for ever. We need to consider the reasons for his mistake and ask if these will continue to apply.

Essentially, Malthus was wrong on both counts: population growth and technical change.

He did not specify the exact rate of population growth, but suggested that with abundant natural resources (as in The New World), population would tend to double every 25 years. In reality world population growth has been much more sluggish than that, doubling roughly every 70 years since 1800. While this has bought precious time, it does not seriously undermine Malthus’ argument that in the long run positive exponential growth will outpace linear growth.

Looking forward, the rate of population growth shows signs of decreasing thanks to the demographic transition. In fact, the populations of the former Soviet Union and Eastern Europe are shrinking, and many advanced economies are struggling with increasing dependency ratios as population growth tapers off and population pyramids become more beehive-shaped. In spite of this, the UN projects global population to continue to increase “by more than one billion people within the next 15 years, reaching 8.5 billion in 2030, and to increase further to 9.7 billion in 2050 and 11.2 billion by 2100”.

As regards technical change, Malthus grossly underestimated the scope for increasing productivity, especially in food production. “The soil of England will not produce much without dressing, and cattle seem to be necessary to make that species of manure which best suits the land”, he wrote (p. 54). He did not – and could not – anticipate the massive substitution of tractors for horses and other draft animals, the comprehensive mechanization of farming, the use of chemical fertilizers or pesticides, the development of higher yielding crops, etc. “Subsistence” (i.e., food production) has not been growing “in an arithmetical ratio”; it has been growing exponentially and at least as fast as population.

But will this continue? Given the projected population increase, it must, and, according to FAO’s 2009 report, How to Feed the World 2050, it can: “The projections show that feeding a world population of 9.1 billion people in 2050 would require raising overall food production by some 70 percent between 2005/07 and 2050.” Despite some qualifications, FAO’s experts believe that “on a global scale there are still sufficient land resources to feed the world population for the foreseeable future, provided that the investments required to develop these resources are made and the neglect of recent decades in the agricultural research and development effort is reversed”.

Yet, in the even longer run we should be concerned for at least three different reasons.

First, being based on the depletion of non-renewable, and in some cases non-substitutable, resources, some of the existing technologies are inherently unsustainable in the very long term. This is the case, for example, with the use of phosphorus. While Malthus was wrong about the necessity of cattle manure, phosphorus is an indispensable element without which plants cannot grow. Estimates of known reserves range from 50-400 years of consumption, but we may well have phosphorus for more than that. Yet, although resource depletion does not appear to be the most imminent threat, the resource will eventually be depleted, with or without growth.

Secondly, it is well-known from physics that the consumption of energy entails the spread of it, not the destruction of it (cf. The Law of Entropy). In the early 1970s, Georgescu-Roegen suggested that the law of entropy would apply to our consumption of non-renewables as well, and the spread of these is a major source of pollution. He even modelled pollution in terms of entropy. While this has been shown to be a theoretical mistake (cf. e.g. Ayres (1999)), the practical relevancy of the argument is hard to deny. The leakage of phosphorus, for example, is a source of eutrophication with blue-green algae blooms and fish kills in lakes and fjords. A similar logic applies to the consumption of other non-renewables (e.g., metals or fossil fuels), the spread of which contributes to a wide range of environmental problems such as antibiotic resistance (zinc), lead poisoning, or climate change (fossil fuels). It certainly is challenging to get the paste back into the tube again, but this is a long-term necessity on board the “Space-Ship Earth”.

Thirdly, although the continued flow of minor technical innovations is unlikely to stop any time soon, the prospects for a major paradigmatic change, a new Green Revolution, are unknown and unknowable. In conclusion, although Malthusian prophecies have been proven wrong in the past, his concerns should not be dismissed too lightly. It is irresponsible to predicate the future on a repetition of the past – or on the hope that “something will turn up”. There are compelling long-term reasons for stimulating innovation to improve resource efficiency to make sure that it will – and prove Malthus wrong once again.


Ayres, Robert U. (1999), The second law, the fourth law, recycling and limits to growth. Ecological economics (29): 473-483.

Georgescu-Roegen, N. 1971. The Entropy Law and the Economic Process. Harvard University Press, Cambridge MA.

Malthus, T.R. (1798), An Essay on The Principle of Population. Printed for J. Johnson, in St. Paul’s Church-Yard. London.

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[1] Malthus wrote more than his Essay on the Principle of Population and should be remembered for more than that. In important respects his Principles of Political Economy (1820) anticipated the ideas of John Maynard Keynes.