The sun was getting low over the East India College. Time for the old professor of political economy to leave for home. His day had been like many. Lectures in the morning, a discussion with colleagues over lunch of some arcane academic matter, a short nap, then answering several letters, and grading student papers. The pleasant event of the day was the arrival of a little book his publisher John Murray had sent him from London. He took the book from his in-tray where his secretary had put it to carry it home with him. Before he put the book into his well-worn leather satchel he held it in his left hand, ready to thumb through it with his right. He paused. The title was a bit bland: 'A Summary View of the Principle of Population". But that described exactly what it was: a summary view of what had become of the theory that he put into the world with his first book, 'An Essay on the Principle of Population,' a book that he had published anonymously more than thirty years ago. He smiled on the thought that he had made his name with an anonymously published book. But now, when his name had become inseparably linked with the theory of population the title page of his new book showed his full name and titles, "by the Rev. T. R. Malthus, A.M., F.R.S." Who else but he could publish a book on the 'Principle of Population'? Population was his bailiwick.
Thumbing through the book, his mind wandered. It all started with long discussions with his father Daniel, a learned man who had grown quite fond of certain enlightenment philosophers. These eminent men imagined utopian, blissful societies whose people lived a life free of misery and want. This, in his mind, was pies in the sky. It certainly was far removed from the lives led by the poor souls of the parish whose young curate he had been at the time. Their lives were miserable and most often short. The only riches that these poor wretches produced in abundance were children. Poor little things they were. Many of them died early and the survivors were often stunted for lack of food. Many of those who reached adolescence left the parish to make their luck in the slimy sickening slums of London. And when he had recently looked over the parish register, it had struck him that the number of births had recently greatly surpassed the number of deaths. How were all these hungry mouths to be fed, their naked bodies to be clothed, and their blank minds directed to proper causes? The utopian philosophers, whose books sold well, knew that reality. But who wanted to read about uncomfortable facts that were, at any rate, visible everywhere? Nevertheless, somehow that reality had to be brought to the notice of the learned men who read the utopian philosophers. How was he to achieve that?
To this day he felt ripples of exhilaration when he remembered the moment when his grand idea about population had struck him. He was on his horse on his way to Okewood where he was to perform a baptism. One more manifestation of the indelible passion of the sexes. If the little poor soul will survive to adulthood she is bound to succumb to the same passion, as will her children, her grandchildren, and so on. Hence, the numbers of her offspring will grow like the numbers in a rabbit warren: 2, 4, 8, 16, 32, and so on. In order to make it into adulthood the baby will have to eat. The food available to a family is, however, limited and doesn't increase with the arrival of another mouth. And what is true for a family must be true for a country and the whole world: when people multiply like rabbits, their numbers are bound to outgrow the available food supplies. That was the basic idea. It was a strong, natural and obvious idea that could be elaborated and embellished.
At Cambridge, where he had studied mathematics at Jesus College, he had learned about functions. These are handy devices to describe and think about the development of quantities of any kind, be it rabbits and grass, or people and food. Moreover, since the great success of Newton, the attention of the learned clerisy was more easily attracted by functions, and for the learned anything mathematical carried in it a mysterious power to persuade. Two functions were needed: one for the population and another for food availability. Rabbit-warren population growth can be captured by a function that increases geometrically. Slowly growing food for sustenance, in contrast, could be he represented by a function that increases linearly. Because a function that increases geometrically will always reach a stage where it grows much more rapidly than a linear function, there must come a time when there will not be enough food for all and when famine looms. That could be the kernel of a great story: a horseman of the apocalypse expressed in terms of mathematics! The book-buying clerisy will lap it up!
This was his model whose structure was as rigid as the carbon bonds in a diamond. Many years after he had published his Essay he was visited by some Mr. Everett, the representative of the United States in the Low Countries. The man new his Adam Smith very well and questioned the arithmetic progression of food production. If the productivity of the workers in a pin factory increases with the number of workers because the workers can become more specialized, wouldn't the same thing happen when the number of workers in agriculture grows? The man had a point. But he decided to ignore the idea which would endanger the main point of his model: geometric progression hitting the arithmetic progression from below. Moreover, Adam Smith was long dead, his book was seldom read, and people in England were now more concerned with misery, want, and hunger than with wealth. There was no danger from old Smith. In place of the increasing productivity of the pin factory he and his friend David Ricardo promoted the idea of diminishing returns. This idea assured that food production would not run away from population growth. If food production could run away from population growth his whole theory about various restraints and positive checks on population growth would be utterly pointless. But not to worry. Ricardo and he had succeeded to immobilize the genie of rapidly increasing food production in the decreasing-returns trap.
He put the Summary in his satchel and left hurriedly. His wife Harriett was not to be kept waiting with dinner.
At the time when Malthus worried about population outgrowing food production, the earth was thinly populated by modern standards - about 1 billion people in total. After Malthus, world population growth accelerated and peaked in the late 1980s. Then it began to decelerate. Some demographers believe that world population will not reach 12 billion before the earth becomes too hot for comfort in about 1 billion years (see Table XX). It would seem that Malthus had a point about the procreation potential of humanity. But what happened to food production? It grew even faster than world population!
The demographer David Lam has compared the development of world population with that of world food production during the period 1960 to 2010, that is when world population growth was as high as it will ever be. The comparison shows that food production growth exceeded population growth (see Fig. XX). The genie has escaped the trap in which Malthus wanted to keep it. We need no longer worry about Malthus's moral restraints and population checks - not for making sure that everybody can be fed.
Fig. XX: World food production, 1961 to 2009. Data are from FAO (2011)
Source: Lam 2011.
What let the genie escape the diminishing-returns trap? It was knowledge, argued D. Gale Johnson in his presidential address to the American Economics Association which he delivered at the start of the current millennium. The demographer Lam agrees. And, were he still alive, Friedrich Engels, the industrialist and financial patron of Karl Marx, could feel confirmed. In 1844, much before Johnson and a decade after Malthus's death, Engels had criticized Malthus for having left science and innovation out of his theory. In contrast to Malthus, Engels suggested, "Even if we assume that the increase in yield due to increase in labour does not always rise in proportion to the labour, there still remains a third element which, admittedly, never means anything to the economist – science – whose progress is as unlimited and at least as rapid as that of population. What progress does the agriculture of this century owe to chemistry alone – indeed, to two men alone, Sir Humphry Davy and Justus Liebig! But science increases at least as much as population. The latter increases in proportion to the size of the previous generation, science advances in proportion to the knowledge bequeathed to it by the previous generation, and thus under the most ordinary conditions also in a geometrical progression. And what is impossible to science?" (Engels 1844).
How helpful is it to say that it was knowledge that allowed agricultural production growth to run ahead of population growth? Perhaps not very. The economic historian Joel Mokyr cautions in 2018, about seven generations after Engels, "The growth of human knowledge is one of the deepest and most elusive elements in history. Social science, cognitive psychologists, and philosophers have struggled with every aspect of it, and not much of a consensus has emerged." To me, this suggests that there is still much room for progress in this field or learning. Accordingly, novices from the next generations of economists that are drawn into this field may have a high chance to make significant, useful contributions.
Sources:
Engels, F. (1844). Outline of a critique of political economy. https://www.marxists.org/archive/marx/works/1844/df-jahrbucher/outlines.htm, Accessed September 7, 2018.
Everett, A. H. (1823). New ideas on population:: with remarks on the theories of Malthus and Godwin. London: John Miller.
Johnson, D. G. (2000). Population, Food, and Knowledge. American Economic Review 90(1): 1–14.
Lam, D. (2011). How the world survived the population bomb: Lessons from 50 years of extraordinary demographic history. Demography 48(4): 1231–1262.
Malthus, T. R. (1830). A summary view of the principle of population. London: John Murray.
Mokyr, J. (2018). The past and the future of innovation: Some lessons from economic history. Explorations in Economic History 69: 13–26.
Our World in Data https://ourworldindata.org/world-population-growth.
Thumbing through the book, his mind wandered. It all started with long discussions with his father Daniel, a learned man who had grown quite fond of certain enlightenment philosophers. These eminent men imagined utopian, blissful societies whose people lived a life free of misery and want. This, in his mind, was pies in the sky. It certainly was far removed from the lives led by the poor souls of the parish whose young curate he had been at the time. Their lives were miserable and most often short. The only riches that these poor wretches produced in abundance were children. Poor little things they were. Many of them died early and the survivors were often stunted for lack of food. Many of those who reached adolescence left the parish to make their luck in the slimy sickening slums of London. And when he had recently looked over the parish register, it had struck him that the number of births had recently greatly surpassed the number of deaths. How were all these hungry mouths to be fed, their naked bodies to be clothed, and their blank minds directed to proper causes? The utopian philosophers, whose books sold well, knew that reality. But who wanted to read about uncomfortable facts that were, at any rate, visible everywhere? Nevertheless, somehow that reality had to be brought to the notice of the learned men who read the utopian philosophers. How was he to achieve that?
To this day he felt ripples of exhilaration when he remembered the moment when his grand idea about population had struck him. He was on his horse on his way to Okewood where he was to perform a baptism. One more manifestation of the indelible passion of the sexes. If the little poor soul will survive to adulthood she is bound to succumb to the same passion, as will her children, her grandchildren, and so on. Hence, the numbers of her offspring will grow like the numbers in a rabbit warren: 2, 4, 8, 16, 32, and so on. In order to make it into adulthood the baby will have to eat. The food available to a family is, however, limited and doesn't increase with the arrival of another mouth. And what is true for a family must be true for a country and the whole world: when people multiply like rabbits, their numbers are bound to outgrow the available food supplies. That was the basic idea. It was a strong, natural and obvious idea that could be elaborated and embellished.
At Cambridge, where he had studied mathematics at Jesus College, he had learned about functions. These are handy devices to describe and think about the development of quantities of any kind, be it rabbits and grass, or people and food. Moreover, since the great success of Newton, the attention of the learned clerisy was more easily attracted by functions, and for the learned anything mathematical carried in it a mysterious power to persuade. Two functions were needed: one for the population and another for food availability. Rabbit-warren population growth can be captured by a function that increases geometrically. Slowly growing food for sustenance, in contrast, could be he represented by a function that increases linearly. Because a function that increases geometrically will always reach a stage where it grows much more rapidly than a linear function, there must come a time when there will not be enough food for all and when famine looms. That could be the kernel of a great story: a horseman of the apocalypse expressed in terms of mathematics! The book-buying clerisy will lap it up!
This was his model whose structure was as rigid as the carbon bonds in a diamond. Many years after he had published his Essay he was visited by some Mr. Everett, the representative of the United States in the Low Countries. The man new his Adam Smith very well and questioned the arithmetic progression of food production. If the productivity of the workers in a pin factory increases with the number of workers because the workers can become more specialized, wouldn't the same thing happen when the number of workers in agriculture grows? The man had a point. But he decided to ignore the idea which would endanger the main point of his model: geometric progression hitting the arithmetic progression from below. Moreover, Adam Smith was long dead, his book was seldom read, and people in England were now more concerned with misery, want, and hunger than with wealth. There was no danger from old Smith. In place of the increasing productivity of the pin factory he and his friend David Ricardo promoted the idea of diminishing returns. This idea assured that food production would not run away from population growth. If food production could run away from population growth his whole theory about various restraints and positive checks on population growth would be utterly pointless. But not to worry. Ricardo and he had succeeded to immobilize the genie of rapidly increasing food production in the decreasing-returns trap.
He put the Summary in his satchel and left hurriedly. His wife Harriett was not to be kept waiting with dinner.
At the time when Malthus worried about population outgrowing food production, the earth was thinly populated by modern standards - about 1 billion people in total. After Malthus, world population growth accelerated and peaked in the late 1980s. Then it began to decelerate. Some demographers believe that world population will not reach 12 billion before the earth becomes too hot for comfort in about 1 billion years (see Table XX). It would seem that Malthus had a point about the procreation potential of humanity. But what happened to food production? It grew even faster than world population!
The demographer David Lam has compared the development of world population with that of world food production during the period 1960 to 2010, that is when world population growth was as high as it will ever be. The comparison shows that food production growth exceeded population growth (see Fig. XX). The genie has escaped the trap in which Malthus wanted to keep it. We need no longer worry about Malthus's moral restraints and population checks - not for making sure that everybody can be fed.
Fig. XX: World food production, 1961 to 2009. Data are from FAO (2011)
What let the genie escape the diminishing-returns trap? It was knowledge, argued D. Gale Johnson in his presidential address to the American Economics Association which he delivered at the start of the current millennium. The demographer Lam agrees. And, were he still alive, Friedrich Engels, the industrialist and financial patron of Karl Marx, could feel confirmed. In 1844, much before Johnson and a decade after Malthus's death, Engels had criticized Malthus for having left science and innovation out of his theory. In contrast to Malthus, Engels suggested, "Even if we assume that the increase in yield due to increase in labour does not always rise in proportion to the labour, there still remains a third element which, admittedly, never means anything to the economist – science – whose progress is as unlimited and at least as rapid as that of population. What progress does the agriculture of this century owe to chemistry alone – indeed, to two men alone, Sir Humphry Davy and Justus Liebig! But science increases at least as much as population. The latter increases in proportion to the size of the previous generation, science advances in proportion to the knowledge bequeathed to it by the previous generation, and thus under the most ordinary conditions also in a geometrical progression. And what is impossible to science?" (Engels 1844).
How helpful is it to say that it was knowledge that allowed agricultural production growth to run ahead of population growth? Perhaps not very. The economic historian Joel Mokyr cautions in 2018, about seven generations after Engels, "The growth of human knowledge is one of the deepest and most elusive elements in history. Social science, cognitive psychologists, and philosophers have struggled with every aspect of it, and not much of a consensus has emerged." To me, this suggests that there is still much room for progress in this field or learning. Accordingly, novices from the next generations of economists that are drawn into this field may have a high chance to make significant, useful contributions.
Sources:
Engels, F. (1844). Outline of a critique of political economy. https://www.marxists.org/archive/marx/works/1844/df-jahrbucher/outlines.htm, Accessed September 7, 2018.
Everett, A. H. (1823). New ideas on population:: with remarks on the theories of Malthus and Godwin. London: John Miller.
Johnson, D. G. (2000). Population, Food, and Knowledge. American Economic Review 90(1): 1–14.
Lam, D. (2011). How the world survived the population bomb: Lessons from 50 years of extraordinary demographic history. Demography 48(4): 1231–1262.
Malthus, T. R. (1830). A summary view of the principle of population. London: John Murray.
Mokyr, J. (2018). The past and the future of innovation: Some lessons from economic history. Explorations in Economic History 69: 13–26.
Our World in Data https://ourworldindata.org/world-population-growth.
