Population and Technological Change

Population and Technological Change is the title of a 1981 book by Ester Boserup. After reading and discussing Paul Ehrlich’s The Population Bomb a few weeks ago, I have wanted to discuss a book with a more pronatalist orientation. The most famous, or at least the one I talk about the most, is Julian Simon’s The Ultimate Resource (second edition here). Compared to that, Population and Technological Change is more academic and more nuanced. I will probably get to Simon’s work later.

Unlike both Ehrlich and Simon, Boserup does not have a clear axe to grind, though she did have well-developed theories about population. She is best known for the model developed in Boserup (1965), The Conditions of Agricultural Growth: The Economics of Agrarian Change under Population Pressure.

I also have some personal news after the main article.

Demand for Food Creates Supply

Boserup’s central insight in Boserup (1965), and discussed in Boserup (1981), is that Malthusian catastrophes with food supply generally do not materialize because food shortages on the horizon will induce a population to intensify agriculture.

In January, I reviewed Thomas Malthus’ “An Essay on the Principle of Population” (Malthus (1798)), the origin of the Malthusian model. The core of the model is that a society’s food supply tends to increase linearly, while population increases exponentially, so it is inevitably the case that the per-capita food supply will decrease to the point of subsistence. The unhappy implication is that the normal state of affairs for humans is a subsistence lifestyle, on the edge of starvation or often falling into it. In the words of Thomas Hobbes, the natural state of life is “solitary, poor, nasty, brutish, and short”.

Due to the persistent failure of the Malthusian model in recent times, it has fallen out of favor as a model for development of human civilization in modern times. However, it is still common wisdom, such as stated in Weil and Wilde (2010) and Roser (2020), that Malthusianism is a good explanation of population dynamics before the Industrial Revolution, and perhaps in contemporary times in nonindustrial areas.

But Boserup argues that Malthusianism has never been a good model. Starting with hunter-gatherer lifeways in the Paleolithic, she argues that when population pressure arose, societies were induced to develop more intensive forms of food production, such as slash-and-burn farming, settled agriculture, and short-fallow cropping.

Each of these techniques, and others discussed in the book, entail a tradeoff between land and labor inputs. More intensive agriculture, by definition, requires less land to produce a given amount of food, but it generally requires more labor. For this reason, Boserop argues that well into the Neolithic, societies continued a hunter-gatherer lifeway unless population pressure compelled them to give that up.

Carey (2023) writes a very readable overview of current understanding of how domesticated agriculture came about. Boserup takes the view that it was motivated by population pressure. However, as Carey documents more than 40 years later, it remains an unsettled question whether agriculture is best understood as a response to population or climactic pressure, or whether the appeal of plant cultivation at the dawn of the Holocene is the best explanation.

Another means of adaptation to population pressure, as Boserup discusses, was the shift to less land- and labor-intensive foods that are less palatable. In recent times, readers may be familiar with stories of the popularity of liver and other unappetizing foods during the Great Depression. Among hunter-gatherer tribes, foods that were rejected during good times were ready alternatives to starvation during bad times. In the post-Columbian era, potatoes and cassava serve as staples among poorer populations.

Pre-Industrial Population Dynamics

Behavioral modernity in humans is believed to date back at least 70,000 years, and the agricultural revolution was a bit more than 10,000 years ago. Obviously, then, the annual population growth rate during that time must have been very close to zero, as no amount of lifestyle adaptation could have accommodated a non-trivial growth rate for such a long period of time. What did that look like?

As noted above, the conventional wisdom is that the Malthusian model applied. Hunter-gatherer tribes perpetually lived at the edge of starvation, and when food was scarce, famine struck. Boserup argues that this was not generally the case even among hunter-gatherers.

For one thing, Borerup argues that natural population growth was not very great in the Paleolithic. Due to disease and risks in childbirth, the average age of death for adult women was 28, giving maybe ~13 years of child-bearing capacity. Furthermore, the mobile lifestyle necessitated that births had to be somewhat spread out.

Second, as I touched on a few years ago in the context of demographic decline in the late Roman empire, it is a persistent myth that prior to the advent of modern contraception, a woman had no means of regulating fertility and had as many children as she was biologically capable of. We should not closely analogize between Roman demographic decline and contemporary fertility trends; unlike at present, for instance, endemic disease was a major factor in Roman demographics. But Roman citizens also practiced contraception, abortion, and infanticide, often to the chagrin of the government. As Malthus (1798) notes, population growth in wealthier European countries was moderated by late marriages.

Boserup argues that, while the importance of these measures should not be exaggerated, hunter-gatherer tribes also practiced similar fertility regulation as the Romans. Kimbrough, Myers, and Robson (2021) find that infanticide was widespread among hunter-gatherers—with rates of 15-50% among modern foragers—though more for the purposes of self-domestication than for population control.

Boserup argues against a Malthusian reading of the extreme mortality of the Black Death, which killed as much as half of Europe’s population from 1346 to 1353. A common hypothesis is that the Great Famine of 1315-1317 weakened the immune system of the population, making them more susceptible to disease. Boserup thinks that this hypothesis is wrong. DeWitte and Hughes-Morey (2013) agree and do not find an association between short stature and mortality to the disease. However, DeWitte and Slavin (2013) (same DeWitte) finds that the Great Famine, but moreso the Great Bovine Pestilence of 1319-1320, left the European population with weaker immune systems and more vulnerability to disease by the arrival of the Black Death. I’ll have to consider this as something that is not clearly established.

One of the major weaknesses of Boserup’s treatment of hunter-gatherer societies is that it relies heavily on extrapolation from contemporary forager societies. As I commented two years ago, doing so can be highly misleading, as there are clear differences between the two. More generally, she is a bit selective with the literature, presenting as fact something that is contested. Finally, because of the book’s age and my own very patchy familiarity with the anthropological literature, I am left wondering how many of her claims have stood the test of time. There is nothing in the book that I know to be wrong, but I can’t have great confidence that it is all correct.

Finally, while overall human population during the late Pleistocene was relatively stable, individual societies grew and decline. Boserup speculates that some societies had long periods of subreplacement birth rates (given high mortality), often to the point of nonviability of the tribe. Then tribes with positive population growth could move into their territory. I am not able to find much evidence to support this model. By contrast, Freeman et al. (2023) present a Malthusian model of repeated overshoot and recession.

Population and Development

Most of what I have written so far was discussed in Boserup’s 1965 The Conditions of Agricultural Growth and revisited in her 1981 book. In Population and Technological Change, she goes beyond agriculture and considers a broader set of changes.

Although Boserup’s book predates it, her model is reminiscent of Kremer (1993), “Population Growth and Technological Change: One Million B.C. to 1990”, which presents a model of how a higher population increases the rate at which new ideas are produced, accelerating technological growth. Under Kremer’s model, the new technology in turn lifts constraints on carrying capacity and allows a greater population. In Boserup’s model, there are several mechanisms by which a greater population enables technological and industrial development.

First is the mechanism of necessity, as outlined above. Agricultural intensification is an example she discusses at length. Another example is how western Europe suffered severe deforestation during the early modern period, spurring the development of coal burning to replace charcoal from biomass.

Another mechanism is the availability of infrastructure. Dense populations can support high levels of urbanization, which in turn create the preconditions for complex industries. She notes that in the middle ages, China had some of the world’s highest population density and thereby was the world’s technological leader. As Europe’s population grew in the high middle ages and again in the early modern period, Europe rapidly caught up with and then surpassed China technologically and became the center of world development. Technological leadership then passed to the United States in the late 19th century.

Population density is required to support sufficient density of roads and railroads, which in turn are necessary for industrialization. She notes that India at the time was an industrial laggard, lacking a good road and railroad network. Most Subsaharan African countries were the same.

Boserup does not make the argument that Julian Simon would make, that a higher population increases the number of people who can potentially come up with ideas. This is what I find to be the most compelling population/technology link.

On Gender and Agriculture

Gender roles are discussed, but not prominently, in Population and Technological Change. However, given that perhaps Boserup’s second most famous work is Woman's Role in Economic Development, I think it is worth mentioning.

Boserup suggests that some statistics on agricultural labor intensity may be misleading because they focus on men’s labor, neglecting the labor that women and children might do. She discusses this specifically in the case of agricultural intensification in Japan, a country with high population density and early urbanization that was compelled to adopt more intensive agriculture early on, partially explaining why Japan became the leader in Asian industrialization.

Curiously absent from the book is discussion on the effect of changing gender roles on fertility rates. Today, it is common wisdom that more career opportunity for women is a major reason that birth rates are declining. Perhaps it is a function of the book’s age that this topic was not addressed.

According to Turner and Fischer-Kowalski (2010), Woman's Role in Economic Development helped inspired the United Nations Decade for Women (1976-1985) and played a major role in establishing contemporary research on the role of women in development. While I would not consider Population and Technological Change an unmixed pronatalist work by any means, it does go to show that, contrary to the impression one might get from contemporary rhetoric, pronatalism and women’s empowerment are fully compatible.

Conclusion

Population and Technological Change is a valuable book. In 211 pages (for the version I have), it covers a lot of ground and does not waste much time with fluff. It is chock full of statistics and cutting edge research. Or, at least research that was cutting edge in 1981. The book’s usefulness is unfortunately diminished by its age. It is also not a very suitable book for the general public, due to a heavy and dry academic orientation, but it is easy to understand for someone looking for something more academic than, say, Paul Ehrlich’s or Julian Simon’s works. I’d say that if you look out for outdated research, it is a useful read for anyone interested in the subject.

Energy and Economic Growth

Last year, I presented at the Markets & Society conference in Fairfax, Virginia on learning curves. I am pleased to share that I will be returning this year, and my topic will be on the role of energy in long-run economic growth. Specifically, should we expect that a breakthrough in energy production will spur broader economic growth in the future?

This topic has been near and dear to my heart ever since I was following the peak oil movement 20 years ago. Major figures in the peak oil movement argued that, since energy is so fundamental to the world economy, a shortfall in the world’s oil supply will cause severe economic dislocations. If we accept this argument (if not necessarily the premise), then it stands to reason that the opposite would be true; development of major new energy sources should drive economic growth.

It was this consideration that motivated me to work on energy policy professionally 10 years ago. Since then, though, I have become more skeptical that this hypothesis actually holds. More specifically, I am doubtful about causation. While it is clearly true that, over the sweep of human history, energy consumption and economic growth are highly related, I now doubt that causation flows from the former to the latter.

After looking at issues around sustainability for the last few months, I would like to turn my attention to drivers of economic growth. Energy is one such hypothesized driver about which I will have much more to say. Population as a driver is something I discussed today and will discuss in the future.

Quick Hits

Most international shipping today is powered by heavy fuel oil, a fuel that is of concern for various environmental impacts. Lloyd’s Register, a technical and professional services company that serves the maritime industry, has a series of analyses of various alternative fuels for shipping. I am intrigued to see nuclear power on this list. Although nuclear shipping is not a novel idea—it is well-established for submarines and aircraft carriers—I don’t have a good sense of how well it will work for commercial shipping. Still, I am pleased to see the industry take this seriously, as I don’t recall nuclear shipping being taken seriously a few years ago.

My attention has recently been brought to the Dead Sea Scrolls, a set of exceptionally well-preserved copies of books of the Hebrew Bible, as well as some apocryphal works and various sectarian manuscripts. The scrolls date from the 3rd century BC to the 1st century AD. Among the significance of the scrolls is that they help affirm that much of the Bible, as we know it today, is in fact faithful to its original form.

The Syrian Observatory for Human Rights, a UK-based NGO that monitors human rights in Syria, has documented massacres of Alawite civilians. The Alawites are an ethnoreligious sect that comprises about 10% of Syria’s population, and it was the sect of recently deposed dictator Bashar al-Assad. The militias responsible for the killings claim that they are fighting remnants of the Assad regime. The new leader, Ahmed al-Sharaa, has vowed to punish those responsible, but given al-Sharaa’s past, it is easy to be suspicious. Sadly, while Assad is gone, Syria’s troubles are not.

In light of recent events, it is worth reading Phillip Magness’ essay on tariffs in the United States, covering the period from the adoption of the Constitution to Cordell Hull’s Reciprocal Trade Agreements Act of 1934. Free trade has been foundational to world prosperity since the end of World War II, and turning from that will be ranked highly among the tragic decisions of the 21st century.

At the National Catholic Reporter, Julie Schumacher Cohen writes of the injustice of the deportation of Mahmoud Khalil, a student leader for pro-Palestinian advocacy. There is much that can be said about this. It wasn’t long ago that many conservatives were raising the banner of “free speech” in opposition to certain social media sites’ content moderation policies. The acid test—what distinguishes genuine advocacy for free speech from empty rhetoric—is whether one will go to bat for speech for a view one disagrees with.