The Curse of Thomas Malthus

Running through some notes from last year, I came across an article by Dietrich Vollrath published in 2017 that I’d printed out to give it proper consideration. It’s called, “Who are you calling Malthusian?”, and it addresses that interesting futures question of why calling someone “Malthusian” is such an effective form of ad hominem attack that it closes down any possible argument.

Poor old Malthus. He has had a bad reputation ever since he predicted, towards the end of the 18th century, that over-population would lead to famine and then to social collapse. It didn’t turn out like that, largely because we stumbled across a one-off supply of cheap energy, and because of the Industrial Revolution. And, because he turned out to be wrong, that means that if you mention Malthus these days you are instantly labelled as a crank.

So Vollrath does us a service in his long post in two ways. First, he tries to create Malthus’ argument in its original context, and second he goes back to the relationships that sit behind Malthus’ model of the world.

Malthusian relationships

The relationships are simple.

One: living standards are negatively related to the size of population. This is because at time of writing the major factor of production was land, whose supply is largely fixed. Vollrath shares a diagram, originally from Greg Clark’s work, which demonstrates this. Peter Turchin’s model in Secular Cycles effectively has this relationship at its core.

Two: population growth is positively correlated with living standards. As Vollrath notes

“This may be because kids are a normal good, and so fertility rises when people have higher incomes. Or it may be because health is a normal good, so people take better care of themselves (and their kids) when they have higher income.”

There’s a third version of this as well, which is that better living standards increased population growth because people were better fed and better clothed, and less likely to die of disease. (There is some work on Black Death survivors that shows that the cohorts with the best survival rates were brought up with more food.) This is likely to be a causal explanation with a lag.

Vollrath also notes that there’s some evidence that indicates that the second relationship might not hold. The data are poor and also ambiguous; different studies conclude different things. But there was no way in which Malthus would have had access to such data.

So to recap, the two propositions underpinning Malthusian economics are:

(1) living standards are negatively correlated with size of population;

(2) population growth is positively correlated with living standards.

Balancing point

FIGURE: MALTHUSIAN RELATIONSHIPS. SOURCE: DIETER VOLLRATH/ DIAGRAM BY THE NEXT WAVE

When you put them together, you get a set of loops: a balancing loop [1] and a reinforcing loop [2].

As Vollrath writes:

Everything in the system is pushing back towards some middle ground where the resource per person, and hence the living standard, is at just the right level so that population growth is zero. With no change in population, there is no change in living standards, so there is no change in population growth, so there is again no change in population. The economy becomes stagnant at the living standard which delivers zero population growth.

Malthus thought that this system would balance at the point of subsistence economics, but Vollrath suggests that this is not necessarily true. The “stagnant” level of living standards can be higher than this, depending on the level of the preference for having kids.

He also makes some other observations on the Malthus model:

• Shocks to technology/productivity temporarily raise living standards but permanently raise population. There is actual data that supports this.

• The adjustment back to the “stagnant” (or stable) level of living standards can take a long time.

In other words, the system can be disrupted in the short-to-medium term if there is a change in technology or environmental conditions which change the relationship between living standards and size of population (the constraining part of the diagram above).

Bargaining power

So that’s Malthusian economics. But there’s also a kind of Malthusian sociology—that changes in population influenced the bargaining power of peasants, and therefore wages, and this then shaped or re-shaped social institutions. There’s a whole set of historical debates here which centre on political power, and on how it’s acquired and exercised. Vollrath touches on some of them.

“North and Thomas argue that changes in population, by changing relative wages and the bargaining power of peasants, were instrumental in changing institutions in Western Europe prior to the Industrial Revolution”. Brenner and Bois, on the other hand, say that “The effect of population changes on labor conditions depended on the actual political power of peasants, which was not necessarily affected by population.”

Political elites

In their book Secular Cycles, Peter Turchin and Sergey Nefedov review the arguments about Malthus in an initial chapter, before proceeding to series of case studies from a range of pre-industrial societies. Robert Brenner’s critique of Malthus, they observe, draws on the period after the Black Death. Different societies that had been similarly affected by the plague followed different paths thereafter. Further, in some countries, such as England, prices and wages followed Malthus’ model, but population growth did not.

They draw on Brenner’s critique to suggest that Malthus’ economic model is missing a couple of important variables: in particular, the system of land holdings in a given territory, and the structure and cohesiveness of the ruling class. In their work, the pre-modern state is a missing variable, in particular the degree to which it co-opts or competes with its ruling elites in the struggle for resources.

Vollrath doesn’t touch on Turchin and Nefedov’s work, and in general the Secular Cycles model isn’t as widely known as it ought to be. In brief, Secular Cycles starts with issues around carrying capacity, and the argument goes like this:

As carrying capacity exceeds limits, you get shortages of land and food, and an over-supply of labour; food prices then increase and real wages decline, which leads to declining per capita consumption, especially among poorer people; this leads to economic distress, with lower fertility levels and higher mortality rates.

FIGURE: SIMPLIFIED SECULAR CYCLES MODEL. SOURCE: THE NEXT WAVE

Prospering twice over

So far, this is fairly Malthusian, but Turchin and Nefedov also look at elite behaviour in these circumstances. Effectively, the owners of land and the employers of labour (often the same people) prosper twice over. In summary, they benefit both because they are employers of labour (and pay less for it) and because they are asset owners (which are bid up by elite competition). Pressure on the poor sometimes leads to political conflict, and sometimes it does not. It depends on whether the elites split or hold together.

Although the case studies are pre-Industrial Revolution, Turchin’s recent work has turned to the more contemporary United States. This probably ought to be the subject of another post, but a world in which growing (global) population leads to falling real wages, steepling rises in asset prices, and intensified elite competition sounds depressingly familiar in 2018.

Limits to growth

Going back to Malthus, then, there’s also a third set of important related arguments, about the nature of the limits to growth. Vollrath characterises “limits” aguments as falling into two schools:

(1) population growth is a given, and does not respond to living standards

(2) population growth reduces living standards (because of resource shortages) and population increases as a result (a negative feedback loop).

The other gap in the Vollrath article is that he uses the phrase “limits to growth” but doesn’t discuss The Limits to Growth, (as in the book and the World3 model). The Limits to Growth is worth considering through a Malthusian lens.

Industrial output

This was one of the criticisms of both the original Limits to Growth model, and the book, and perhaps this had more intensity at the time because Paul Ehrlich had just written his very Malthusian Population Bomb, which projected that the burgeoning global population would lead to famine in the very near future. It’s worth noting that it came out just as global population growth hit its highest rate.¹

Of course, the Limits to Growth model is more sophisticated than this (here’s my version of it, from a previous post).

And there are some critical points that are worth identifying. The Limits to Growth model isn’t directly about population, except to the extent that rising population might correlate with increased industrial production. Industrial output is a function of non-renewable resources and industrial capital (this is a type of ‘factors of production’ model). Industrial output increases “persistent pollution”, which is a modelling catch-all for–broadly–environmental externalities; critics sometimes make the mistake of reading the word too narrowly or too literally. This then reduces agricultural production, which means that industrial output falls. In turn, this means that the industrial base cannot sustain such a large population.

And as Dennis Meadows has said a hundred times or more since it was first published, in the face of this systemic change, technology can only delay collapse within a given system. The main case (“standard run”) of the World3 model, which tracked the behaviour of the world system fairly closely from 1971 and 2000 (and may still be doing so), leads to industrial decline in the late 2020s, and population decline a decade after that.

Just unlucky

So one is left with the thought that Malthus might just have been unlucky with his timing. It would have been hard for him to know that the small workings of coal he might have been able to observe were in fact a foretaste of the large scale mining  of the 19th and 20th centuries, or that we’d stumble across more more-or-less free energy in the shape of oil in the 20th century.

That leaves the wider mystery of why Malthus, and “Malthusian” have become, in effect terms of ideological abuse. The use of the term “Malthusian,” at least in my lifetime, has been a form of lazy and personal attack that then permits the speaker to ignore what was actually said.  It can’t just be that Malthus was wrong; many of his contemporaries were wrong about things and have merely become historical footnotes.

The reason, I think, is that Malthus casts a doubt over the whole notion of progress and growth that has been our dominant discourse for the past 150 years, certainly in the countries that did well out of the Industrial Revolution. More: it has been our only permissible mainstream discourse. And if Malthus was unlucky in his timing, his argument still implies that we might, as a species, have been lucky rather than clever in stumbling across all of that easy energy. Which, in turn, casts a doubt over a large part of the story about human capacity and human development that is the story of the Enlightenment.