Why did the Roman Economy Decline?

Wednesday, August 24th, 2016

Peter Brown of Princeton University is one of Mark Koyama’s favorite historians of late antiquity, but Koyama doesn’t agree with Brown’s explanation for why the Roman economy declined:

In The Rise of Western Christendom, Brown summarizes the new wisdom on the transition from late antiquity to the early middle ages. He accepts that this transition brought about an economic decline — a decline evident in the radical simplification in economic life that took place. Long distance trade contracted. Cities shrank and emptied out. The division of labor became less complex. Many professions common in the Roman world disappeared.

All of this is relatively uncontroversial. At issue is what caused this decline? Traditional accounts emphasized the destruction brought about by barbarian invasions and civil wars as the frontiers of the Western Empire collapsed. These accounts emphasized a collapse in trade and increased economic insecurity. Brown, however, argues that the bulk of modern research rejects this old fashioned view.


The barbarian invasions, of course, play a role in this story because they put pressure on the Roman state. But their role is peripheral. Rather, Brown contends that the Roman state was the engine of economic growth of late antiquity. Turning on its head the old view associated with Michael Rostovtzeff that attributed the decline of the Roman economy to high taxes imposed by the Emperor Diocletian and his successors, Brown argues that these high taxes were in fact the source of economic dynamism.


The collapse of the Roman state was catastrophic, not because the Roman state was an engine of economic growth, as Brown contends, but because it provided, albeit imperfectly, the public good of defense. In the absence of this, transactions costs greatly increased, long-distance trade declined, markets contracted, and urbanization declined.

The notion of a Malthusian Trap helps explain how high taxes — especially efficient land taxes — might help, rather than hurt, per capita income.

Malthus was Late

Sunday, January 19th, 2014

Malthus was wrong, Matt Ridley says, but Malthus wasn’t wrong, Steve Sailer notes — he was late:

Gregory Clark’s A Farewell to Alms documents, using English public records such as wills from 1200 to 1800, that the English over these 600 years were using Malthus’s 1798 advice to engage in “moral restraint” avant la lettre. The chief mechanism was not exposing babies on mountainsides or whatever, but was simply delaying marriage until a couple could afford the various accoutrements appropriate for their class.

How different in that regard was Jane Austen’s world from today? Some, but the similarities should be obvious.

The average Englishwoman married during these centuries between 24 and 26. In contrast, the average Chinese woman married around 18. Thus, the Chinese population would grow faster, but tended to collapse when good government broke down.

In contrast, most of sub-Saharan Africa didn’t have to worry about Malthusian traps until fairly recently. Population density outside of a few nice highland locations tended to be well below the agriculture capacity of the enormous amount of land. Diseases, competition with co-evolving wild animals (especially elephants, who consumed crops if there weren’t enough people around to drive them off), and lack of fortifications meant that much of Africa tended to be underpopulated. The great African fear was not overpopulation of a region, but of humans dying out all together in an area.

Thus, while European culture tended to encourage sexual restraint, African culture tended to encourage sexual exuberance — a pattern we can still see today in America.

Sailer seems to think that “the very young average age of first marriage for American women in the 1950s compared to previous decades represented a zenith of mass prosperity,” but Malthus noted the same pattern in 1798:

In the United States of America, where the means of subsistence have been more ample, the manners of the people more pure, and consequently the checks to early marriages fewer, than in any of the modern states of Europe, the population has been found to double itself in twenty-five years.


But the English North American colonies, now the powerful people of the United States of America, made by far the most rapid progress. To the plenty of good land which they possessed in common with the Spanish and Portuguese settlements, they added a greater degree of liberty and equality. Though not without some restrictions on their foreign commerce, they were allowed a perfect liberty of managing their own internal affairs. The political institutions that prevailed were favourable to the alienation and division of property. Lands that were not cultivated by the proprietor within a limited time, were declared grantable to any other person. In Pennsylvania there was no right of primogeniture; and in the provinces of New England, the eldest had only a double share. There were no tythes in any of the States, and scarcely any taxes. And on account of the extreme cheapness of good land, a capital could not be more advantageously employed than in agriculture, which at the same time that it supplies the greatest quantity of healthy work affords much the most valuable produce to the society.


The population of the thirteen American States before the war, was reckoned at about three millions. Nobody imagines that Great Britain is less populous at present for the emigration of the small parent stock that produced these numbers. On the contrary, a certain degree of emigration is known to be favourable to the population of the mother country. It has been particularly remarked that the two Spanish provinces from which the greatest number of people emigrated to America, became in consequence more populous. Whatever was the original number of British Emigrants that increased so fast in the North American Colonies; let us ask, why does not an equal number produce an equal increase, in the same time, in Great Britain? The great and obvious cause to be assigned, is the want of room and food, or, in other words, misery; and that this is a much more powerful cause even than vice, appears sufficiently evident from the rapidity with which even old States recover the desolations of war, pestilence, or the accidents of nature. They are then for a short time placed a little in the situation of new states; and the effect is always answerable to what might be expected. If the industry of the inhabitants be not destroyed by fear or tyranny, subsistence will soon increase beyond the wants of the reduced numbers; and the invariable consequence will be, that population which before, perhaps, was nearly stationary, will begin immediately to increase.

Population Models

Friday, February 6th, 2009

On the site for their new book, The 10,000 Year Explosion, Cochran and Harpending share some “deleted scenes” that didn’t make it into the book, including this piece, which examines some simple population models and demonstrates an interesting result when you add a lethal disease — malaria, in this example — into the mix:

There is more than half again as many resources per person now than there was before malaria appeared. What this means on the ground is that people do not have to work very hard to get enough to eat, that there is fruit on the trees for plucking, and that there are not great labor demands on anyone.

Gregory Clark (Clark 2007) points out that the medieval Englishman had a higher standard than a medieval Japanese because there was much more sewage and filth in England and so a heavier burden of disease. This extra disease translated, as in our malaria example, to a lower population density and higher standard of living.

What are the social consequences of this new disease for our population? The most important immediate consequence is that there are plentiful resources for everyone and so, following the nature of the creature, males withdraw from subsistence work as they find that they can simply parasitize women for food. In much of central Africa the result is societies in which men don’t do anything very useful and women provision themselves, their children, and the men. The euphemism in economics for this kind of society is “female farming system.” Left free of the demands of subsistence we expect the men will start hanging out together, perhaps even all moving into a village men’s house (not so common in Africa). This may soon lead to local and regional raiding and warfare and an entrenched culture of local violence.

The warfare itself may cause enough excess death that a female farming system is sustainable even in the absence of a killer disease. Highland New Guinea, for example, seems to have had a classical cad system for millennia or more. (Ethnographic shorthand for societies where males put a lot of effort into competition with other males is that they are cad societies as opposed to dad societies where male effort is directed to provisioning a male’s own family.) Of course there are other contributing factors here like the extremely broken terrain that makes the establishment of a larger polity with an effective constabulary difficult or impossible.

The Culture of Prosperity

Tuesday, September 9th, 2008

Wolfgang Kasper examines The Culture of Prosperity while reviewing Gregory Clark’s A Farewell to Alms, comparing Clark’s lists of pre- and post-industrial vices and virtues to Jane Jacobs’ lists of cultural attributes for the guardian moral syndrome and the commercial moral syndrome (from her Systems of Survival):

To my mind, Jacobs’ list fully circumscribes the decisive cultural qualities that Clark keeps mentioning in his book. Anyone who has spent only a few days working in different cultures will realise how influential and pervasive these differing attitudes are. During three days’ work, say, in Shanghai, you will have had several discussions about moral principles and been asked numerous times for advice. During three days in Nairobi or Lima, you will have been informed repeatedly by the privileged that they expect donors to provide aid and that the condition of the country is the consequence of colonialism; you can also expect to come across some dishonest double-dealing. And everywhere you will probably observe some hair-raising maltreatment of machinery.

Table 1: Moral syndromes: guardian and commercial

(Hat tip to Arnold Kling.)

The Malthusian Trap

Tuesday, March 18th, 2008

Arnold Kling’s recent review of Gregory Clark’s A Farewell to Alms reminded me that, although I’ve discussed it before, I’ve been meaning to write something more substantial, now that I’ve read the whole book myself.

Clark emphasizes the Malthusian Trap that pre-modern societies face. He explains it briefly in How To Save Africa:

Before the Industrial Revolution all societies were caught in the same Malthusian Trap that imprisons Africa today. Living standards stagnated because any improvement caused births to exceed deaths. The resulting population growth, pressing on fixed land resources, inevitably pushed incomes back down to subsistence.

But living conditions did vary across pre-industrial societies. Perversely, rich societies were those where nature or man created high death rates. In such settings living conditions could be good as long as the population did not grow. In the Malthusian era, what is now vice in economic policy — violence, poor public health, war, inequality — was virtue in terms of living standards. And what is now virtue, vice.

The African environment has always created high disease mortality. This was a blessing for Africa’s living standards. Before the Industrial Revolution, Africa was rich, with material consumption probably double or triple that of China, Japan, or India, and as good as that of Europe. For example, when the British were looking for cheap labor in East Africa in the 1840s they had to turn to India for low-wage workers. Asian living standards were low because of high standards of personal and public hygiene in preindustrial China and Japan. This condemned Asia to subsistence on a minimal diet. Europeans in contrast were lucky to be a filthy people who bathed rarely and squatted happily above their own feces, stored in basement cesspits. Filth engendered wealth.

Most of the world, thankfully, has escaped the topsy-turvy logic of the Malthusian era through the Industrial Revolution. Living standards are now independent of population levels, so any reduction in mortality is an unalloyed blessing.

In a pre-modern economy, wealth production is almost entirely a function of arable land. Pre-modern humans aren’t much different from herd animals, in that sense, because the land can only support so many hungry mouths. An additional farm hand doesn’t produce anywhere near as much additional food as he consumes. More people means less food per person, which means more misery, with fewer children surviving into adulthood and fewer adults surviving into old age.

Thus, anything that kills people off — especially if it kills them quickly, rather than crippling them — reduces the number of mouths to feed by more than it reduces the amount of food produced. Plagues and wars are terrible for the victims, but good for everyone else — because a pre-modern economy is almost zero-sum.

But it gets weirder. Note that Clark mentions violence, poor public health, war, and inequality. In a Malthusian society, terrible inequality does not make the lower classes worse off, at least not in the long term; it just makes them fewer in number. No matter what, they’re going to be miserable enough that deaths match births — but if the ruling class skims more off the top, the ruling class can live at a higher living standard without reducing the living standard of the lower classes. Again, the downtrodden masses will be, in the long run, miserable either way. It’s just a question of how numerous they’ll be.

The only way out of this Malthusian Trap is to grow production faster than the population can grow — and to sustain this economic growth — something that didn’t happen until the Industrial Revolution.

Without rapid, sustained economic growth, the only other alternative to misery is keeping the population down. The South Pacific islanders achieved their worldly paradise through infanticide. Christian Europeans clearly did not approve, put an end to the practice, saw populations increase dramatically, and watched living standards drop precipitously. Similarly, modern aid agencies provide “needed” medical care to poor Africans, making sure that they live long, impoverished lives. As Clark points out, “Modern medicine has reduced the material minimum required for subsistence to a level far below that of the Stone Age.” Life is full of unpleasant ironies.

And that’s why it’s hard to get excited about malaria nets and foods engineered to kill intestinal worms. They simply reduce the material minimum required for subsistence to a lower and lower level. (Such “solutions” are only helpful to the degree to which they reduce long-term disability.)

In fact, as long as a society makes such improvements in dribs and drabs, the population will keep up, and the result will be a more complex, potentially more fragile society, with no higher standard of living. Joseph Tainter’s The Collapse of Complex Societies points to this idea, without the emphasis on the Malthusian element — or so I surmise from reading excerpts and reviews; I haven’t read the book (yet).

Jared Diamond points to a similar notion in Collapse: How Societies Choose to Fail or Succeed. A society will short-sightedly grow, and grow, and grow, until “suddenly” it can’t support itself. Humans have a long history of not being much better than herd animals when it comes to matching their own population to the carrying capacity of the land. In fact, even forward-looking humans have a tendency to “eat their seed corn” when the seed corn isn’t literal corn, and no one owns it — when it’s water stored in underground aquifers, or wood growing in nearby forests, or fish swimming in the sea.

Of course, the modern “peak oil” crowd thinks we’re facing exactly that kind of situation now, consuming vast amounts of energy that were stored in the earth’s crust over not just years, decades, centuries, and millennia, but millions of years. What happens when you build an entire economy on energy stores that will run out in a few centuries?

Perhaps an Industrial Revolution allows society to break out of the Malthusian Trap in the short run, and, while still out of the trap, to develop the knowledge and skills to avoid falling back into it. Even if we’ve relied on fossil fuels so far, our modern economy has uncovered the benefits of broad innovation, of large numbers of intelligent humans building on each other’s discoveries and refinements. Let’s hope that the Net sets us free.

Bryan Caplan’s Critique of A Farewell to Alms

Monday, September 24th, 2007

In A Farewell to Alms: Overview of My Critique, Bryan Caplan starts by criticizing Gregory Clark’s understanding of Malthusianism:

Even worse, Clark repeatedly misstates the implications of his own model. He delights in counterintuitive claims like “[I]n 1776, when the Malthusian economy still governed human welfare in England, the calls of Adam Smith for restraint in government taxation and unproductive expenditure were largely pointless.” To the contrary, even in a Malthusian model, more production and less waste is unambiguously good for living standards. Population growth eventually returns living standards to their original level, but that may take generations.

I don’t see that contradicting Clark’s Malthusian point at all. He clearly recognizes that population growth only eventually reduces living standards. As he says in How to Save Africa:

Before the Industrial Revolution all societies were caught in the same Malthusian Trap that imprisons Africa today. Living standards stagnated because any improvement caused births to exceed deaths. The resulting population growth, pressing on fixed land resources, inevitably pushed incomes back down to subsistence.

But living conditions did vary across pre-industrial societies. Perversely, rich societies were those where nature or man created high death rates. In such settings living conditions could be good as long as the population did not grow. In the Malthusian era, what is now vice in economic policy — violence, poor public health, war, inequality — was virtue in terms of living standards. And what is now virtue, vice.

(Emphasis added.)

Caplan’s second point is that Clark ignores the power of institutions and policies:

He also ignores massive, long-lasting policy disasters like Communism; comparisons between West and East Germany, and North and South Korea.

A commentor, Jason Malloy, notes that Clark doesn’t ignore those policy disasters; he just takes a much longer view of history:

You may disagree with his conclusions, but he doesn’t ‘ignore’ Communism, which he argues dissolved in an eye-blink of history, consistent with a view that destructive institutions are in an unstable balance with the evolved dispositions of the population.

This complaint is the one I’d like to focus on though:

In the face of all this evidence, Clark throws up his hands and says that economists don’t know how to create growth. Give me a break. If voters and politicians around the world since 1800 had just done what Adam Smith told them to do in The Wealth of Nations, poverty would already be a thing of the past. Economists have known how to create growth for centuries. The problem is that, all too often, non-economists choose not to listen.

(Again, emphasis mine.)

While I largely agree with him, perhaps we should attempt to solve the larger problem of actually creating growth, rather than the fairly narrow problem of coming up with a “solution” that won’t get implemented.

Institutional changes prerequisite to the industrial revolution

Tuesday, September 11th, 2007

In discussing Gregory Clark’s A Farewell to Alms, Nick Szabo counters Clark’s claim that England experienced no significant institutional improvements from 1300 to 1800. Here is his list of institutional changes prerequisite to the industrial revolution:

  • The mechanical clock, 14th century. The resulting rise of clock culture and the time wage may have slowly but radically improved the coordination and work habits of Europeans. Earlier adaptation to clock culture, a process that may take centuries to evolve, may explain the large discrepencies between European and many non-European laborer work habits that Clark cites.
  • The printing press and the rise of book consciousness, which radically decreased the costs of teaching economically important knowledge to both children and adults. The rise of book consciousness, reflected in the literacy and book cost data Clark graphs, explains the most prominent puzzle revealed by Clark’s data: the fact that skills and innovation rose dramatically even as the rewards to skills were stagnant or declined.
  • Nationalization the Church in England and secularization of family law, 16th century.
  • The incorporation of the Lex Mercatoria into the common law, and the resulting rise of modern contract law, 18th century. Indeed, much of this occured in the same decades as the start of the industrial revolution.
  • The “Romanization” of property law, rendering land more freely saleable, divisible, and mortgageable, which Adam Smith noted was an important improvement still in process at his time.
  • The rise of marine insurance (e.g. Lloyd’s of London) and the associated rise of colonialism and world trade, 17th-18th century.
  • The decline of guilds and monopolies, 16th-18th centuries. Medieval England was certainly not a highly competitive market economy. Commerce in goods was dominated rather by monopolies and a variety of price and quality controls instituted by guilds and towns.

Farewell to Alms, pp.112-192

Wednesday, August 29th, 2007

Tyler Cowen discusses Farewell to Alms, pp.112-192 and again spawns some fascinating discussion. Read the previous installment, if you haven’t already.

A Farewell to Alms, pp.1-112

Wednesday, August 22nd, 2007

Tyler Cowen discusses A Farewell to Alms, pp.1-112 and spawns some fascinating discussion. Read the whole thing.

A Farewell to Alms

Thursday, August 9th, 2007

Nicholas Wade reviews Gregory Clark’s A Farewell to Alms for the New York Times:

Gregory Clark, an economic historian at the University of California, Davis, believes that the Industrial Revolution — the surge in economic growth that occurred first in England around 1800 — occurred because of a change in the nature of the human population. The change was one in which people gradually developed the strange new behaviors required to make a modern economy work. The middle-class values of nonviolence, literacy, long working hours and a willingness to save emerged only recently in human history, Dr. Clark argues.

I’m surprised this hypothesis was “allowed”:

The basis of Dr. Clark’s work is his recovery of data from which he can reconstruct many features of the English economy from 1200 to 1800. From this data, he shows, far more clearly than has been possible before, that the economy was locked in a Malthusian trap — each time new technology increased the efficiency of production a little, the population grew, the extra mouths ate up the surplus, and average income fell back to its former level.

This income was pitifully low in terms of the amount of wheat it could buy. By 1790, the average person’s consumption in England was still just 2,322 calories a day, with the poor eating a mere 1,508. Living hunter-gatherer societies enjoy diets of 2,300 calories or more.

“Primitive man ate well compared with one of the richest societies in the world in 1800,” Dr. Clark observes.

The tendency of population to grow faster than the food supply, keeping most people at the edge of starvation, was described by Thomas Malthus in a 1798 book, “An Essay on the Principle of Population.” This Malthusian trap, Dr. Clark’s data show, governed the English economy from 1200 until the Industrial Revolution and has in his view probably constrained humankind throughout its existence. The only respite was during disasters like the Black Death, when population plummeted, and for several generations the survivors had more to eat.

Malthus’s book is well known because it gave Darwin the idea of natural selection. Reading of the struggle for existence that Malthus predicted, Darwin wrote in his autobiography, “It at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. … Here then I had at last got a theory by which to work.”

Given that the English economy operated under Malthusian constraints, might it not have responded in some way to the forces of natural selection that Darwin had divined would flourish in such conditions? Dr. Clark started to wonder whether natural selection had indeed changed the nature of the population in some way and, if so, whether this might be the missing explanation for the Industrial Revolution.
Generation after generation, the rich had more surviving children than the poor, his research showed. That meant there must have been constant downward social mobility as the poor failed to reproduce themselves and the progeny of the rich took over their occupations. “The modern population of the English is largely descended from the economic upper classes of the Middle Ages,” he concluded.

As the progeny of the rich pervaded all levels of society, Dr. Clark considered, the behaviors that made for wealth could have spread with them. He has documented that several aspects of what might now be called middle-class values changed significantly from the days of hunter gatherer societies to 1800. Work hours increased, literacy and numeracy rose, and the level of interpersonal violence dropped.

Another significant change in behavior, Dr. Clark argues, was an increase in people’s preference for saving over instant consumption, which he sees reflected in the steady decline in interest rates from 1200 to 1800.

“Thrift, prudence, negotiation and hard work were becoming values for communities that previously had been spendthrift, impulsive, violent and leisure loving,” Dr. Clark writes.

Around 1790, a steady upward trend in production efficiency first emerges in the English economy. It was this significant acceleration in the rate of productivity growth that at last made possible England’s escape from the Malthusian trap and the emergence of the Industrial Revolution.