On Malthus
A quick note on sources
I’ve pulled from a lot of sources for this essay. This lecture series from Greg Clark at UC Davis was immensely helpful. So was Jared Diamond’s Collapse. I also referred to Nick Szabo’s series on Malthus. This includes Malthus and Capital, Trotting Ahead of Malthus, and Two Malthusian Scares. For the section on population, I referred to Hans Rosling’s book Factfulness, and his TED Talk on global population growth.
The Malthusian Dilemma
Introduction
This essay will focus on a problem that is already solved. People often pretend that it isn’t. But it is. At the very least, this essay should help you identify when those worrying about resources are justified and when they are not. At the very most, it’s both instructive and uplifting to see how humanity has escaped an existential threat before, especially as we face many of our own.
The most common description of the Malthusian Dilemma is, “Food production improves linearly and population grows exponentially. Therefore, food production cannot keep up with population growth.” This explanation is understandable and straightforward, but I think there are more helpful ways to frame the problem.
First, we get a clearer picture of food production by evaluating its inputs (workers, land, and productive capital) and its outputs (food). The term "linear growth" means that it increases at a steady rate, which isn't quite true of pre-industrial agriculture. Instead, farmers faced something much closer to diminishing marginal returns.
Second, population growth is better understood using birth rates (average children per woman) and child mortality rates. A steady reproduction rate would be two children per woman surviving to reproductive ages (replacing both the mother and the father), and an unsustainable rate would be anything higher.
Exponential is an accurate term for population growth. Each additional person can potentially reproduce themselves. So, even a reproduction rate of two and a half will grow the population more rapidly than you may expect.
With this in mind, a more accurate description of the problem is “our food production was hitting a point of diminishing marginal returns too early to keep up with exponential population growth.” It has less of a ring to it but adds some much-needed clarity.
Underlying Assumptions
We broke free from the Malthus during the Industrial Revolution. So, the following assumptions (and the basis for the Malthusian Dilemma) concern pre-industrial societies.
The wealthier people were, the more children they had.
The wealthier people were, the longer they lived.
More people led to less wealth per person.
These three assumptions, when true, led to the following cycle of misery: Underpopulated and relatively wealthy community → excess birth rates → overpopulation → too few resources per person → a disproportionate number of deaths. This cycle would then repeat.
For the sake of brevity, I’m going to treat assumptions one and two as givens. In pre-industrial societies, both were nearly always true. Assumption three—more people led to less wealth per person—is the most important and least straightforward. That’s where I’ll focus.
More people led to less wealth per person
As states grow, each additional person (1) contributes to the group and (2) takes some of its resources. This trade-off is the essence of the eternal immigration debate. In the United States, Democrats argue immigrants will contribute positively to the economy (which they will), and Republicans say that they’ll take jobs (which they also will). Both sides are correct, but we have to determine which is more important at the moment. Do we need lower unemployment or more economic growth? As the times change, so does the right answer.
Pre-industrial societies were constantly at a point where additional people required more resources than they could give in return.
Diminishing Marginal Returns
Imagine two economies. In economy one, there is $100 total. If the population is 10, everyone has $10. When an 11th person is added, his contributions bring the total wealth of society to $121. Now, the average individual earns $11. The additional worker contributed more than he took away, and everyone is slightly richer.
In economy two, there is $100 total and a population of 10. On average, everyone has $10. Then, an 11th person is added. His contributions bring the total wealth of the society to $105. Although the total wealth still increased, the average person lost money. The ten-person society had an average wage of $10, and eleven person society had $9.54. This additional worker took away more than he contributed, and everyone is slightly poorer.
To escape Malthus, the additional worker must contribute more than (or, at least, equivalent to) the average income. Otherwise total wealth increases, but the average person becomes slightly poorer, and the cycle continues.
Regarding immigration: Democrats expect economy one, Republicans economy two.
Pre-industrial societies began like economy one. But, as they grew larger they became more like society two. The earlier additions are more likely to increase the average wage, and the later additions less likely. The 25th worker did not add nearly as much value as the 11th. This could be understood more simply—when there are fewer people, there is more to be done.
Diminishing marginal returns — after some optimal level of capacity is reached, adding an additional unit of production will result in smaller increases in output.
This gives us a little hope. If food production is always linear, then we have to solve the problem on the population end. That’s not great. Instead, the food production begins increasing rapidly and then slowly dies off. So, we can ask: why do we get less food as we get more people? What changed? This framing makes the problem a little more solvable.
Why did pre-industrial societies face diminishing marginal returns?
Pre-industrial output relied on labor, capital (animals, buildings, etc.), and land. Labor and capital could increase continually. But the land supply was (and still is) ultimately fixed.
Because land supply does not change, people get less land when the population increases. Less land leads to less output. It isn’t easy to find more land, but (!) there is a third input: productive capital.
Productive Capital — the system or tool used to produce goods and services
Pre-industrial societies would hit an early tipping point of diminishing marginal returns because (1) they had a fixed amount of land split up amongst more and more people. And (2) they were not accumulating enough productive capital to offset this loss.
How did this affect society?
The Cycle
Returning to our initial assumptions: the population determines the average income, and the average income determines the birth and death rates. This creates a cycle.
Population (N) → Average Income (y) → Birthrate (B) & Death rate (D) → Population (N)
Pretty bleak. How did we change this?
Escaping Malthus
Accumulating Productive Capital
To escape Malthus, we needed to accumulate more productive capital. Then, each additional worker would produce more output and require less land, and the wages would continue to increase as the population grew. The breaking point seems to have been with transportation, which allowed us to more effectively (1) acquire productive capital, and (2) distribute our food. This boost created a virtuous cycle.
Specific Productive Capital and Virtuous Cycles
Britain was the first to escape Malthus and did so with multiple simultaneous productive feedback loops. Nick Szabo beautifully describes two of the most important loops. Both revolved around transportation.
The first was the fodder, horse, coal, and lime cycle (as you'll see, all four are forms of productive capital). At some point, we improved our fodder in two ways: it was both healthier and more abundant. This improvement led to stronger horses, which could transport things more effectively and cheaply. The most important thing they could transport was coal, which was essential for heating, fuel, and burning lime. Farmers used burnt lime to de-acidify soils, which allowed for significantly better farming. This technique, in turn, allowed for even better and even more fodder, which completed the virtuous cycle.
Another critical cycle involved horses, institutions, markets, and specialization. The stronger and more plentiful supply of horses, plus innovations in sailing, improved the transportation of goods. This development allowed for access to trade between societies separated by longer distances. The exchange allowed for a more excessive division of labor, creating a "cheese country," "salting country," etc. Ultimately, one of these regions specialized in breeding horses, completing the virtuous cycle.
Limes allowed for more productive farming, and transportation allowed for specialization. Combined, the two helped individuals to do less with more and push the needle beyond Malthus.
These virtuous cycles prove the first half of Malthus’s argument (that food production improves linearly) incorrect. Food production leads to other improvements in society, which, in turn, improve food production. Malthus was missing the premise that healthier food is an exponential technology.
Don’t Eat Your Milk Cow
These virtuous cycles didn’t happen earlier for many reasons, but Szabo mentions two. First, people often put the accumulated wealth toward luxury or military buildup instead of investing it in productive capital. Second, poor harvests often led to the destruction of capital. That would leave long-term issues.
For example, farmers often had cows produce milk for their families every year. But, if they had a poor harvest one year, and their family is about to starve, they eat their milk cow. They survive the year but cannot produce milk now or in the future, a long-term issue that was difficult to overcome.
So, remember: Don’t eat your milk cow.
Development and Family Planning
So, the first half of the Malthusian Dilemma was mistaken: improvements in food production are not always linear. How about the second half? Will our population always grow exponentially? Nope. That’s wrong too.
For a while, it appeared population growth would increase forever. But, we seem to be reaching a light at the end of the tunnel. Hans Rosling’s Factfulness does an excellent job of showing this phenomenon. Here is a graph from his website, where you can also find a video explanation.
Birth rates flatten as families escape extreme poverty. They no longer need child labor on their farms or insurance against child mortality. Women who escape poverty quickly become educated and gain access to contraceptives, both of which lead to lower birth rates. For the majority of the world, this is already a reality. In Factfulness, Rosling wrote, “UN experts are not predicting that the number of children will stop increasing. They are reporting that it is already happening.”
Eradicating extreme poverty → less child mortality, better education, and access to contraceptives → naturally lower birth rates.
This point hasn’t been reached by everyone. The population continues to increase from high birth rates in the most impoverished communities, and the most effective antidote to unsustainable population growth is helping these people achieve better lives. Then, advances against childhood mortality, education, and access to contraceptives will do the rest. Once this is fully accomplished, flattened birth rates and low childhood mortality will lead us to a new equilibrium—somewhere near eleven billion.
As the world population reaches its new equilibrium, we will no longer need to increase our productive capital to avert starvation. That doesn’t mean we shouldn’t continue economic development. We should, and productive capital will still improve our living standards. But, at the very least, people will not immediately starve if we face stagnation. That’s good news.
