Omer Moav on the Emergence of the State
Mar 6 2023

grain-tax-200x300.jpg Since at least Adam Smith, the common wisdom has been that the transition from hunter-gathering to farming allowed the creation of the State. Farming, so went the theory, led to agricultural surplus, and that surplus is the prerequisite for taxation and a State. But economist Omer Moav of the University of Warwick and Reichman University argues that it wasn't farming but the farming of a particular kind of crop (but not others) that led to hierarchy and the State. Moav explains to EconTalk host Russ Roberts storability is the key dimension that allows for taxation and a State. The conversation includes a discussion of why it's important to understand the past and the challenges of confirming or refuting theories about history.

Rachel Laudan on the History of Food and Cuisine
Rachel Laudan, visiting scholar at the University of Texas and author of Cuisine and Empire, talks with EconTalk host Russ Roberts about the history of food. Topics covered include the importance of grain, the spread of various styles of cooking,...
Brook on Vermeer's Hat and the Dawn of Global Trade
Timothy Brook, professor of history at the University of British Columbia and author of Vermeer's Hat: The Seventeenth Century and the Dawn of the Global World, talks with EconTalk host Russ Roberts about the expansion of global trade between Europe...
Explore audio transcript, further reading that will help you delve deeper into this week’s episode, and vigorous conversations in the form of our comments section below.


Mar 6 2023 at 10:11pm

What an interesting episode. Thank you, Russ. I’ve worked in development for twenty years and never came across the tuber-grain angle as explanation for the (lack of) emergence of states.

Mort Dubois
Mar 7 2023 at 7:48pm

What about religion?  I would imagine that faith has been intertwined with power dynamics in almost every human society.  This paper is talking as though a subset of economic factors is all there is.

T Sean Schulze
Mar 8 2023 at 3:57pm

Another episode that has me thinking in several different directions.

My first thought, thinking about the idea of marauding bandits charging a “tax” to protect the growers of foodstuffs, was that the brain charges the body a tax of oxygen flow and nutrients to get the other specialized cells out of danger, find additional sources of nutrients, and build teams with other groups of cells external to the body itself.

My second thought was that the “tax” that marauding bandits charged growers might not be such a bad thing. To quote a phrase, “It’s complicated.” The bandits presumably have a leader. His followers, the other bandits, charge him a tax, which we now call a “wage,” to be part of his group. They won’t stay with the band if doing so does not provide nutrition. So, he has to make it worth their while to stay with the group and continue to protect the grower. We can’t think of the grower and “marauding bandits” both as single atomic units. The marauding bands were made up of individuals each looking out for his own survival and the survival of his family just like the grower.

As these groupings and arrangements continue and get more complicated, “protecting” takes on other aspects as well, such as enforcing contracts the grower may make with other growers — at task we now look to governments and states to do now as well.

The difference in how these organizations emerged and evolved based on what the growers were growing is very interesting, but for me, it highlights how really multifaceted the whole issue is.

Jon Hardy
Mar 9 2023 at 7:46pm

Alfred W. Crosby in “Germs Seeds & Animals” touches on the importance of the Columbian Exchange (referring to Chris Columbus’ re-discovery of America) in introducing American crops like potatoes to the Old World and diversifying and maximizing European crop production. Also I think to some extent Jared Diamond in “Guns Germs & Steel.”

Luke J
Mar 11 2023 at 11:20pm

The potatoes I buy can stay on my kitchen counter for weeks. Wouldn’t a constable or mafia soldier easily collect tuber taxes once monthly in a village or small town?

Mar 13 2023 at 1:01am

I think the idea is that tubers can be left in the ground until needed so you just dig up what you need each day, and run away when the tax collector comes.  If the farmers had a bunch of grain stored in a dry structure it would be easy for the tax collector to find, but harder to start digging around for tubers.

Richard W Fulmer
Mar 13 2023 at 3:53pm

There’s a problem with the “roving-bandits-become-stationary-bandits” theory: until an agricultural community is “acquired” by stationary bandits willing to protect it, it’s a “commons.” That is, every group of roving bandits has an interest in taking everything and leaving nothing behind for rival groups of roving bandits. That being the case, how could an agricultural community ever have gotten started unless it was either geographically isolated or located in a defensible spot?


Suppose on the other hand, that early agricultural communities developed their own warriors to protect them. These domestic fighters later evolved into stationary bandits – that is, elites who taxed the farmers to provide for their own sustenance. From the outset, then, the domestic bandits would have had an interest in not “shearing the sheep” too closely, and the communities could become established. Occasionally, a community’s domestic bandits might have been overwhelmed by foreign, roving bands, which then took over the franchise.

Gregory McIsaac
Mar 15 2023 at 6:52pm

Interesting and plausible analysis of the value of grains vs. tuber crops in the development of “the state.”  But as far as the difficulty of taxing or stealing tubers, I suspect that farmers did not specialize exclusively in tubers, in part because tubers tend not to have much protein. Early farmers probably also had some livestock, hunting and/or fishing activity. And it is not difficult to imagine ways that bandits or tax collectors could extract some value by demanding some of these higher value products, such as by threatening violence against farmers’ families or confiscating tools.

I think a problem with taxing or confiscating tubers is not so much that they remain in the ground year round because that is not the case in climates where the ground freezes.  I suspect a larger disincentive to taxing or stealing tubers is that tubers are bulky and of low value. Bandits and tax collectors would have to expend considerable energy to transport them after confiscating them.

An exception to this occurs in the Andes, where the dry and cold climate allows for freeze drying of potatoes after fall harvest, thereby providing longer shelf life and reducing the problem of bulkiness. This may be one of the few locations where a “state” developed based largely on tuber production.

A side note: there is a tradition in west Africa (and perhaps elsewhere) in which a family preparing a meal is obligated by culture to invite any stranger passing by their dwelling to join their meal.  I suspect this is based on a hunting and fishing tradition, in which catch and kill are uncertain and sometimes greater than one family can consume.  Communal sharing of hunting and fishing bounty is a way of cultivating good relations with neighbors and each family may reduce their risk of suffering from temporarily low success at fishing and hunting.  Perhaps this could also be a basis for state formation.

Greg Silverman
Mar 19 2023 at 12:54am

I do not understand how Moav can ridicule the theory that agricultural surplus is a necessary condition for a tax base that can sustain a state.

A food surplus is more than what is needed to sustain the current population. When the tax collector takes the state’s share of the harvest they prevent the current population from growing as much as it could but leave enough, on average, for the current population to sustain itself. That is, the state is getting into a steady state where it defines what the producers’ surplus is so they can sustain themselves and the state can sustain itself.

So, an agricultural surplus in a crop that is “taxable” is his theory.


Comments are closed.


Watch this podcast episode on YouTube:

This week's guest:

This week's focus:

Additional ideas and people mentioned in this podcast episode:

A few more readings and background resources:

A few more EconTalk podcast episodes:

More related EconTalk podcast episodes, by Category:

* As an Amazon Associate, Econlib earns from qualifying purchases.

TimePodcast Episode Highlights

Intro. [Recording date: January 23, 2023.]

Russ Roberts: Today is January 23rd, 2023, and my guest is economist Omer Moav of Reichman University and the University of Warwick. He is the host of the Hebrew language podcast, Osim Heshbon, and he is the author with Joram Mayshar and Luigi Pascali of "The Origin of the State: Land Productivity or Appropriability?" which was published last year in the Journal of Political Economy and is the subject of our conversation today.

Omer, welcome to EconTalk.

Omer Moav: Thank you, Russ.


Russ Roberts: Now, your paper is an attempt to understand where hierarchy and the state come from, and it's an incredibly creative and ambitious work.

I want to start with a question you don't really deal with in the paper, because in papers like this, you don't deal with these things, but that is: What do you mean by the state? I was telling my son about this upcoming podcast. He said, 'The state--what do you mean, the state?' Economists use it to mean a certain thing. For non-economists, non academics, what do you mean by 'the state' and what do you mean by 'hierarchy'?

Omer Moav: Well, it is a relevant question of course, and it is well-defined when we go to the empirical part of the paper, because then there's data, and data sets tend to be well-defined. However, what we care about, and maybe that's a difference between economists and political scientists or anthropologists, is not the definitions, but the main ideas.

So, in our view, a state is an organization in which there is a strong elite which controls what happens, more or less, and taxes the masses. That's a state. So, when income flows from the masses, historically farmers, to the central state, and the state could do stuff with this income, like provide law and order, military, attack others, build pyramids, whatever.

Russ Roberts: And some of it--the pyramid part is for the benefit of the elite, presumably. Sometimes it would be called confiscation or confiscatory taxation. But other times it's going to provide what economists mean by public goods--you called it law and order, but it would be some power to police, some power to maybe some modes of transportation, clearing roads, and so on.

When we think about ancient times--which of course we have a very imperfect picture, and one of the challenges of this paper, and part of the creativity of it is how you try to get at that--when we think about ancient times, we think about the transition from hunter-gatherers to agriculture. So, somebody used to run around with a spear and now they're running around with a hoe or seeds or some kind of agricultural implement. Where's the state?

I mean, I'm a farmer now: What does that mean, a state? I could think about Ancient Egypt, but when I think about this transition period in these very early days, how might it have mutated from nothing to something?

Omer Moav: So, first, I'm pretty sure it was a very gradual process. But, it's an interesting point that you raise and very important one, which is that the state emerged, I would say, in stages, more complex hierarchies emerged, eventually states, following the transition from hunting-gathering to farming, the so-called Neolithic Revolution.

And, that's actually an important question: Why is it that following the Neolithic Revolution we see the rise of these complex hierarchies and states? And, part of what we do in this paper is actually refute the existing theory. And, in that sense, this is what makes this paper, I think, really important, on the one hand side.

On the other hand side, we had a very hard time to publish it because when you refute existing theories where many researchers are committed to, invested in, then they give you a very hard time as a referee. So, we really suffered. But, eventually, we're really happy that it was published in the Journal of Political Economy. I should mention this is one of the top, top journals in economics. And, luckily, the editor in this journal actually went against the negative and hostile referee.

Russ Roberts: It's ironic because I just recorded an episode that hasn't been made public yet, Omer, where we talk about the perilous path of peer review and referee reports and how strange it is: that, if peer review was really a successful enterprise, when your paper was rejected, it would be over. You'd have to write something else. But, instead in academic life, you send it to a different journal. Now, you happened to send it to one of the--personally, I think the top journal in economics. I went to the University of Chicago; I'm totally biased. But, you're giving us an example of how strange this process is. You're saying that the peers who reviewed the paper didn't like it so much, but the editor didn't agree. But, I'm curious, relevant--

Omer Moav: Well, you know, Russ, if you open this, I could talk for at least an hour about, and provide many examples of how awkward, and I would say even corrupt, like mafia-wise, this process is to a large extent.

But, talking about the mafia, let me just say something which is really important. Back to the paper, you ask, 'What is a state? How did it come to emerge?' And, I think that today we tend to think, especially in liberal democracies, that the state is this benevolent organization; that we pay taxes, but there is this contract that the state gives us in return--stuff, all the public goods and so on and so forth.

But, historically, I think that the better view of a state is, as Mancur Olson published in his 1993 article, is just roving bandits turning stationary.

So, a state is a transition from random crime to organized crime. And, historically, I think that's a very accurate description. So, the state is a powerful elite that could tax the masses and take care of its own good. That doesn't mean that this is bad for the subject, because you should compare. I ask people, 'Is it good to have a mafia organization control your life?' 'Well, yes, if the alternative is just random crime.' So, in a sense, it was a win-win transition to some extent, but this is debatable.


Russ Roberts: When you think about that, the roving versus stationary bandit, if I'm a band of hunter-gatherers and we have a good kill--we kill a couple large animals and we're excited--and someone comes along and takes them, then we move. We don't want to stay in the same place. We want the bandits to have to find us again, and we hope we can find a place where the animals are and the bandits aren't.

But, once you are in agriculture, you're stationary. You can't move. And you do become vulnerable to theft. And, the bandit who used to track you down in the field, hunting, now knows where you are; and they become stationary. The stationary bandit is the Mancur Olson model.

And of course, there's a temptation for the ignorant bandit to take all your crops, burn down your house, and move on. But, the bandit realizes at some point that, 'No, it's not a bad thing if I leave something for the farmer. The next year they can continue to farm and I'll get some more next year.'

So, it's not the bandit that we see in the movies who takes all the gold from the stagecoach. Rather, there's a symbiotic relationship there, when the bandit becomes self-interested in the wellbeing of the farmer, and that's why it's not as evil in terms of impact as it might otherwise be.

Omer Moav: Yeah. It's just like modern mafia, in the sense that what do they do? They charge for protection. It's not just really protection from themselves. You pay them not to attack you: that's mainly part of the deal. But, they also protect you from others, and that's the organized crime. And, organized crime is a more efficient outcome than these roving bandits that just take everything and burn your house.

But, Russ, maybe we should go a step back or move into--okay, so what are we saying in this paper that is new? To say that, I need to first explain briefly at least the conventional theory.

Now, when I say conventional theory, this is something really, really huge. You go back 200 years, you read Adam Smith, even thinkers before Adam Smith. You read and they tell the same story, more or less. And, you look at papers and books today that deal with the emergence of hierarchies and states, it's always--almost always; I should be careful--the same variant of the following story.

The transition to farming allowed increased output. Farmers could produce more food than hunter-gatherers. And, with more food, they could actually produce surplus--so, more food than they need for their own consumption.

And, this surplus is a prerequisite for taxation and the emergence of states.

So, the story is the farmers produce surplus. Once there is this surplus, someone could take it away. It could be roving bandits, but it could be stationary bandits. And, here you go, you have hierarchies. Organized crime turn into chiefdoms and states, and so on and so forth. And the, there are variants: Is it a benevolent state or is it just a predatory state? These are details.

Now, we started working on this about 17 years ago, and just published less than a year ago. So, it was quite a long process. It started with a process of thinking about the issue. And, the main thought we have is that if you read Thomas Malthus and you read this story, there is a contradiction. If Malthus is right, then there is no surplus, because population will adjust to eliminate any surplus. That's the basic Malthusian theory: higher fertility, if there is life above subsistence. And, as a result of increased population, income per capita declines back to the level of subsistence, meaning no surplus. So, that's the main flaw we found with this literature.

But, in addition to that, here is a thought: Let's do the following thought-experiment. Imagine a village that, say, grows some kind of cereal--barley, wheat, rice. Now, what is typical about cereal is that it is seasonal. So, the harvest typically takes place within a very short time in the year. And then, even if there is no surplus, the farmers have to store it for their survival throughout the year.

Now, suppose a tax collector arrives after the harvest is finished: all the crop is stored, and the tax collector arrives with a little army. Think of, for instance, Ancient Egypt. A tax collector on behalf of the Pharaoh arrives to the village and says, 'I came to tax you. Give me 20% of your crop.' Well, the head of the village could say, 'Sorry, I don't have any surplus this year.' What would the tax collector say? 'Oh, my apologies. I will try my luck next year?' Of course not. Even today, you cannot tell the government, 'Sorry, I don't have any surplus.' So, of course, in historical times, this claim is ridiculous. 'You don't have surplus, so what? I see the grain here, I'll just take 20%.' 'Oh, but some people will die.' 'Well, who cares?' We're talking about history, who care. Today, in many places, people don't care about death of innocent people, so of course, historically, this was the case.

So, this just simple thought-experiment illustrates that the idea that surplus is a prerequisite for taxation is just wrong.

But in addition to that, let's do another thought experiment. Think about a village that actually has a lot of surplus, but the surplus is not a grain: but it's like a root or a tuber. Think of cassava, for instance. Cassava is a good example, because as long as--it's a root that is in the ground. And, as long as it is in the ground, it stays. It's very well stored. But, once the farmer takes the root out of the ground, within a few days, it rots.

Now, what would do a tax collector if there's lots of cassava in the ground? How do you move it from the farming area to build, say, pyramids or to provide the military? It's just impossible.

So, you see, surplus is also not a sufficient condition. What you really need is not surplus, but a food that is easily taxed. And, that's the main claim we make.

Now, we're not--yeah, go ahead.

Russ Roberts: I was going to say, when I read that--you have just a little additional piece you have to add, and we'll get to that in a minute--but: I'm done. It's a really great paper. It's really interesting. To try to show that that's historically relevant is quite challenging, and we'll talk generally about how you try to do that. It's hard to do and you concede as much.

But, the fundamental idea that storability is crucial is profound.

The other thing you have to add, of course, is that cassava can be grown throughout the year. You can grow it at different times, harvest it at different times. So, the cassava grows, or the potato, and you eat it. Then you plant some more and you eat it. Or you've planted some more in between, and it's occasionally showing up and you're eating it.

Whereas, the grain shows up once and you have to store it. So, it's wonderful that it can be stored; but it's horrible because it can also be taxed. But the cassava has this fabulous--I mean, it's fascinating. I think you're the first people to notice this, is it--it's horrible, cassava, because you can't store it, but it's fantastic because it can't be taxed.

Now, the next question would be a very blunt, simple question, not subtle--

Omer Moav: But, let me just, because I want to be really accurate and not to take credit to myself, which is unjust. So, the idea that it's easier to tax grains than cassava or other roots and tubers is not ours. We were not the first to make it.

The contribution of our paper is to say that the surplus argument is wrong. And that's--you could point--James Scott is famous for that with his two bestsellers, The Art of Not Being Governed and Against the Grain. But, in fact, he was not--he got a lot of credit, but there's already researchers from the 1970s and 1980s that made similar arguments.

But, the difference is that they basically took the standard conventional theory about surplus, but they say, 'Look, surplus is important, but it should be surplus of something that is taxable,' meaning storage is required and it is storable.

And, our contribution--our theoretical contribution--is to say: Surplus argument is wrong; you don't need surplus.

Moreover, of course, the main thing that we do is we go to the data and then we really prove our arguments--

Russ Roberts: As best you can.


Russ Roberts: But--but--the part that's interesting, to me, is that you have a choice as a farmer. You can often--not always, I assume there's land productivity issues--but you could choose to grow cassava or you can choose to grow grain. And, the next insight of the paper, which I think is fantastic, is that it's the gap--it's the relative productivity of grain versus tubers that's important. Because if you can grow a lot more grain relative to cassava or potatoes, even though it's going to get taxed, it's still worth it. And, that's a choice that I assume--not always, but sometimes or often--a farmer has to make.

And, that's fantastic. Because, I mean, that's economics. It shows you the choice that the farmer has to make. And you presume, which is always a good starting place, that farmers are going to try to do something that's good for them--as opposed to, say, they have a religious or cultural love of the tuber, or whatever it is, that pretty much this is going to be a central issue.

So, my next question is, first of all, what part of the world can you grow tubers in versus grain? And, what part of the world can you grow both? Is that everywhere? or almost everywhere?

Omer Moav: Yeah. So, there are maps in the paper. Unfortunately, I don't have them at hand now to show you, but there are very large parts of the world in which only roots and tubers are available. Large parts of the world that only cereals are available. But, large parts of the world in which both are available.

And indeed, our theoretical model has farmers who could choose between roots and tubers or cereals, but the productivity difference is what matters. So, cereals, also in the data in our model, are more productive than roots and tubers. If roots and tubers are more productive than cereals, that's an obvious choice. Then of course, I grow the crop that gives me more and is not taxed. But, then there is this trade off you described.

And, indeed, when cereals are more productive--sufficiently more productive--and there is a government, it is a hierarchy, it is if you wish organized crime that could commit to a reasonably low tax; and then the farmers say, 'Okay, if the tax is sufficiently low, it's a win-win. I will grow the cereal and the government will tax me, but I'm still better off.' Of course, if these are just roving bandits out there, I could still just stick to the less productive roots and tubers.

Russ Roberts: Yeah--I just want to bring in one of my favorite insights of economics, which is that through much of history, life is not zero-sum. It's negative-sum.

So, if I'm growing something--or I have livestock or I have something valuable that can be taken from me--the potential that it can be taken from me, which is a zero-sum thing on the surface. In other words, you take my grain; you have it, I don't; total amount of grain doesn't change, in theory. But of course, in reality, it does change, because it changes the incentives to grow grain. And, that's why it's negative sum, at least at the early stage, where the banditry is just taking it, as opposed to providing things of value to the farmer in the form of public goods.

But, the other part that people forget is that the potential for my stuff to be stolen means that I will spend resources to prevent it. And, that is the negative-sum part.

So, if I want to get rich, in the old days, I take your stuff. That's not zero-sum, that's negative-sum. Because that means two things. You're going to spend real resources to keep me from stealing it, and you're going to avoid producing really wonderful things that you can't protect, because I'll just steal them if I'm stronger than you. So, I either have to have in my own private army or locks or hide things. I have to expend resources. So, theft is not zero-sum. It's negative-sum.

And, the power of the state in these early versions, I assume, where it was mainly just taking stuff, but leaving enough for you to keep you somewhat whole is very costly because it means it reduces my incentive to grow as much grain as I might. It depends. It could go the other way, too. It's complicated. But, certainly, it could induce me to be less productive. I could grow tubers instead.

And, the last thing I just want to clarify is that because there are places that only grow grain, and because there are only places that can grow tubers, your theory has a prediction, which is that the state should not emerge in the tuber places and should emerge in the grain places.

Omer Moav: The prediction is actually stronger than that, because even in places in which you have both grains and tubers, if the tubers are sufficiently productive, the farmers would choose to grow tubers.

Let me just add another issue, which is, since you raised it, the differences between regions is really a puzzling question. So, why is it that some places that adopted farming developed these sophisticated hierarchies, leading to the early city states of Mesopotamia and then the central state of Egypt, but other places like New Guinea, which adopted farming at the same time as Egypt, just stayed with this, nothing much, small tribes that keep on fighting each other?

What is the conventional story?

Well, lowland productivity. In areas, mainly tropical areas, where you could see the very strong correlation, tropical areas are the areas in which states fail--and don't function well, still today. And, historically, they didn't exist. These are areas in which land productivity is low, according to the conventional story. So, with low land productivity, no surplus, no state.

Now, what we say is a different story.

In areas in which land is highly productive, but it is roots and tubers or other stuff that is hard to tax, like taro or bananas or other fruit and vegetables, these are places that hierarchies would not emerge.

Now, we call it the curse of plenty. Because eventually, although in the short run, the farmer is better off growing something that cannot be taxed; but, that means the state does not emerge. And in the long run, these are worse places, because states, even if these are mafia-type states, are better off for economic development and the welfare of the population, than just random, roving bandits or small tribes that fight each other all the time. And of course, once we move to a more democratic liberal state, then obviously economic development is better.

And you know, the key thing, without getting into the debate about what a modern state should do--should it provide health and education and everything? Or just law and order? Well, just law and order is crucial. We need the protection of property rights. And, these regions in which states did not emerge, have very weak institutions, weak protection of property rights; and this is a curse. And, so, again, the curse of plenty.

Russ Roberts: And, that comes back to my point about theft being a negative-sum game. It's very hard to escape low levels of material wellbeing if you don't have secure property rights. End of story.


Russ Roberts: Now, before we go into some of the empirical challenges of trying to assess whether your theory is right, I have to raise an awkward question. Which would be: why should I care about this? Okay, there was this goofy theory once that it was land productivity that led to the state, why should I care? I care; I'm interested. But in general, when we think about these attempts to understand pre-modern history, where often you get involved in what I call just-so stories: There's a narrative that emerges after the fact that's consistent with some of the things. People cherry-pick. There's a thousand books we won't name that try to explain this arc of human development from hunter-gatherer to agriculture to the city state, to the modern times. We care a lot about it, I think for all kinds of reasons. But, I'm curious why you think we should care. Why is this work important? Is it important?

Omer Moav: So, suppose I will tell you that research on ancient history could actually contribute to economic growth. Then obviously it's important. But, then I could ask, 'But, why is economic growth important?' You'd say, 'Oh, well that increases welfare.'

But, then I have a shortcut. If this is interesting, you read something interesting, as human beings, we are curious about our history. So, we enjoy reading stuff that helps us understand what happened in the past. Why do people do research on dinosaurs? Who cares? Well, we care. That's a matter of fact. We care about what happened in the past. We care about what happens in remote stars and so on and so forth.

But, let me just say another thing, is that there is a lot of research that shows the persistence of institutions. And, in this sense, I think the paper is not just about the emergence of states. It also helps understand why some states today are failing states, why others are successful. And, a lot of the economic research on economic institutions just highlights the quality of institutions. But, in a large extent, I would say is not very successful in going to the root cause of better or worse institutions. And, I think this paper is really important in understanding that.

Russ Roberts: So, there is a book called The Dawn of Everything, by David Graeber and David Wengrow, which I've thought about reading. I started, I've looked at it. Their claim, for what it's worth, I think, is that getting the pre-modern history right helps us imagine what is possible now.

So if, for example, it turns out that the evolution of the state is not necessary for civilization and growth and flourishing and so on, maybe there are ways of organizing our economy or our government that we can't, seemingly, imagine because we're so burdened by the status quo of the present. So, I think that would be another argument.

I think your work forces the reader to think about what government's actually doing when it taxes. We have a lot of narratives about it, romantic narratives in some cases.

I think in your case, in mine, we're a little less romantic about the state. We look at it and say, 'Maybe this is not a healthy way to look at it.' And, I think when you read about the history and you try to understand why it evolved the way it did, you can open your mind to other possibilities. I would just add that as another value.

Omer Moav: Okay, that's an interesting take on that. I'm not sure I'm fully convinced by their argument, but I could say that if you think of, really, these questions: why do we have in most of Western countries, states, governments that control about half of the income, government spending? Why is it so high?

And, if you go back to the 19th century, it was extremely low compared to--like, 10%, 15%. Then it jumps within a short time to 45%, 50%. What happened there? So, there are various stories. I don't want to go into them. Democracy and the demand for more services. I ask myself, 'If a democracy wants more taxes, obviously dictatorship wants more taxes, right?' So, why?

And of course, it's not the transition from tubers to grains in the early 20th century, but it is income tax, accounting, large firms. And, it's a similar argument, because it's taxability. So, once the economy is organized in a way that it's easier to tax, governments will tax more.

And then, ex post, we give it some rationalization from a benevolent point of view. But, in a large extent, governments tax because they can.

Russ Roberts: Yeah. We had a recent episode on the strange world of cryptocurrency in Argentina. And, I suggested--I think this was such an alien idea to most listeners, but not to most economists--that when the state infrastructure is sketchy, not well-designed and not respected by the citizens, the government no longer has an easy way to fund its activities, whether they're lovely activities or not so lovely. Whether it's confiscatory taxation or whether it's to provide things that actually many of the citizens want. And, in many of those situations, the government resorts to inflation as a way to raise money for its activities.

And, I think non-economists--outsiders, everyday people--look at that and go, like, 'Well, that's stupid. Inflation is really destructive. Why would you do that?' The answer is: Because it's better than the alternative. It's like your mafia point. Yeah, the mafia is horrible, but there are advantages to it. Compared to what, is always the right question.

So, anyway, I think that's just another way to say what you're saying.


Russ Roberts: So, you have this claim: it's a lovely claim. And again, as I said, as most of my economic intuition: I'm done. I love this paper. I love the idea of it.

But, it would be nice if it were true.

So, you do your best; and you concede early on--you have a beautiful paragraph where you say, "We acknowledge that none of our empirical investigations provide full proof for our thesis." Very rare sentence in a published economics paper. But, that's always the case. But, you admitted it, which is great.

So, the challenge is that you have this claim. It's about the past. And of course, it's about relative productivity of different kinds of products, agricultural products. And, a lot of those products don't exist anymore. We have the modern versions of them. So, talk about some of the things that you tried to do and did do to try to get at the validity of the claim.

Omer Moav: So, let me first just clarify to those who are not researchers in economics, that suffer from what happened to our profession.

So, what really happened over the last 20, 30 years, that just having a good idea and a nice theory and some data that support it is not sufficient.

And, in fact, to a large extent, unfortunately, our profession even lost interest in logical claims and theory. And, today, what people want to do is not understand the world, but know the facts. And, this is the identification revolution. So, to identify causal effects.

Now, don't get me wrong: Identifying a causal effect is extremely useful and important. But, we should remember this is the mean, not the goal. The goal is to learn something about reality. So, now, when people do randomized control trials--and in that sense economics became like a true science--you take a random sample and you randomly allocate treatment to one half, and the other half is the control group, and everything else being equal, you could really identify the causal effect of the treatment.

But, of course, questions that could be quite important, or at least very interesting, one cannot randomize treatment. They cannot randomize countries with roots and tubers. That just doesn't work.

So, what we do, instead of one perfect experiment, we look at various data sets. And, we try to show that--we look at different data sets, different ways to--a proxy for roots and tubers, different periods of time and different statistical methods, and to show consistency. And, the end result is that in all our specifications, once we control for the type of crop, the surplus theory has zero statistical significance.

Let me just clarify what I just said now.

So, the experiment we do or the data analysis that we do--repeatedly with different data sets--the main idea is to have this variable, which is some proxy of hierarchy or states. And that would be what we call the left-hand side variable: the variable of interest.

And, we run a statistical test or a horse race, using a linear regression on many variables. But, the horse race is between two competing variables. One is some proxy for land productivity, and another is a proxy for cereals. What is the main thing we use to start with, would be data from the food and agriculture organization, which has estimates for any area in the world: What would be the output if you grow there, potatoes, cassava, all the main roots and tubers and all the main cereals?

So, we take their data, which translates the predicted output to calories--so it's comparable, right? A ton of tubers is not a ton of cereal, so you need to translate it to calories. We're not the first to do it.

And then, we calculate for each unit of land or unit of observation, depending what we have on the other side of the equation, what is our units.

For instance, just to set ideas, we look at the ethnographic atlas, which has some 200 societies around the world with data about their hierarchy, their location, what kind of crops they grow, if at all.

And so, we look at their location: where they're physically located. And, then, for the land they're on, we calculate the advantage of cereals over roots and tubers. That would be our proxy, whether they grow cereals or not.

And, we calculate just land productivity: that would be the maximum calories they could produce based on this FAO--Food and Agriculture Organization--data.

Now, if you just run an Eve[?] Test of the conventional theory, you could actually see that there is a very strong correlation between land productivity and hierarchy. But, once you throw in a control for cereals, it kills the positive effect of productivity on hierarchy, and you see a positive effect of cereals on hierarchy. I say 'effect' and not 'correlation' because we don't use the data on whether they actually grow cereals or not. We use a proxy, an instrument for cereals. So, it's something exogenous. It's a geographical measure of the suitability of land for cereals. That's the most simple empirical exercise we do. Very strong results.

A), It shows that indeed, when land is more suitable for cereals, that's the place farmers grow cereals. And, when land is not very suitable for cereals, or where tubers are similarly suitable, farmers grow tubers.

And then, the next stage is indeed, this is highly correlated with emergence of hierarchies.

But, that's just one test, and it's a cross section. So, of course, one could have many concerns about the validity of that. So, we cannot alleviate all these concerns.

Let's do a different test. Here we do something which is quite interesting, which alleviates all concerns about a cross-section analysis. And, what we do is we look at the changes and hierarchies, which is basically the emergence of new states following the Columbian exchange. So, when Christopher Columbus discovers America, following this discovery, we have the so-called Columbian exchange. What is that? Crops--and not just crops, also disease, and other animals--move from the Old World, which is Europe, Asia, and Africa, to the New World, Americas. And also, they move in the other way.

So for instance, cassava, a very important roo--not in most Western societies, but in Africa today, cassava is one of the two major sources of calories. The other is corn. Both of them come from the New World, did not exist in Africa before the Columbian exchange. So, corn did not exist in the Old World. Cassava did not exist. Sweet potato, white potato did not exist.

On the other hand side, in the New World, from the major cereals, they only had corn. So, with the Columbian exchange, we get the transition of rice and wheat and barley all going to the Americas.

So, what do we do now? There's a different data set which looks at countries--the borders of countries today--and this data sets is over time. So, every 50 years, based on reading archeology and history, they define whether this piece of land is a state, a chiefdom, or just a tribe.

So, we take the data as is, and we ask, 'Could the change that happened in land productivity following the Columbian exchange?' Right? So, land productivity increases in price because suddenly you have crops that are more productive. So, could that explain the rise of countries? Answer?

Russ Roberts: No.

Omer Moav: It cannot. It doesn't. Well, maybe I shouldn't say it cannot: It doesn't. So, you look at the data, you see that a lot of areas, land productivity improved, but that doesn't explain the emergence of hierarchies. Whereas, the increase in the advantage of cereals over roots and tubers, this does explain.

So again, it's a very different empirical exercise using panel estimates. So, over time, rather than just a cross section. Using a different data set of hierarchies, a different period of time: exactly the same results. Not land productivity, but the suitability for cereals. So, it's the crop that matters.

But, that's not enough. So, we do more than that, because you really need to convince the skepticals and especially people who want to protect the theory they're engaged and invested in.

And, we want to go further back in history, closer to the point in time in which the transition really happened.

So, now you might say, 'Well, the food and agriculture organization data is based on modern crops.' The modern crops are not the same as the historical crops, because the mother of the wheat, 10,000 years ago, is not the wheat today. There was so much genetic breeding by farmers over time that it's a very different crop.

And this goes on: You could mention the green revolution. So, that is just 60, 70 years ago, and a huge change--genetic change--in crops to make them more suitable for human beings.

So, instead of that, we use an alternative proxy. Actually two alternatives proxies. One is quite simple. This was existing data. So, farming started, according to archeologists, identified something like 20 different points in the world in which farming started. It didn't start in one point and spread everywhere. There are 20 centers of domestication.

So now, here is an interesting proxy: the proximity of each unit of land to a center of domestication.

What our data shows is that what really matters for the emergence of hierarchies, proximity to a center of domestication of a cereal. Roots and tubers do not matter--simply have no positive effect on the proximity to roots and tubers, do not have an effect.

Now here, what we do, since we go back thousands of years, it's not states anymore that we look at. The data we look at is archeology.

So, we basically draw lines on the globe, every one degree North, South, every one degree East, West. And we get these chunks of land. And, for each chunk of land of this size, we first look at the proximity to a center of domestication. And, then we count 'stuff' that we find in this unit of land--stuff that indicates hierarchy, like ancient cities, temples, castles, pyramids, quarries, and so on. And we ask, 'What explains these findings?' And, the answer is cereals, not land productivity.

And, the last thing that we do is another data set that we actually build. And that took us more than a year, with cooperation with the diversity organization--oh, I forgot the exact name--but an organization that looks at the distribution of wild plants in the world. And the question we ask--and we're the first to do this. Jared Diamond in his book, Guns, Germs, and Steel, exactly talks about crops that are available for domestication, but he doesn't have the data. Or then, there were some research done later with some data, but the entire research had data points which is continents. And, what we have is very detailed data. We know where exactly in the world, what's the spread of the genetic parent or genetically related crops, wild crops, wild relatives of each domesticated crop. So, we know where the wild relatives of wheat are, where the wild relatives of barley, of cassava--all these major staple crops today.

And then, again, we divide the world to these blocks, as we do, and we count archeological findings. And, here is what we find. If you divide the world to four types of units of land. One, only cereals are available for domestication. The other, only roots and tubers are available for domestication. Then, of course, there is none, and both.

What do we find? Well, hierarchies emerge where cereals are available, but roots and tubers are not. Places that only roots and tubers are available, you don't see the emergence of hierarchies. Places that both available are very similar to places that only roots and tubers are available.

And, that's exactly the theory we discussed earlier. That farmers, once they have the choice, they prefer to grow roots and tubers and they enjoy the protection that they provide. But this is the curse of plenty.


Russ Roberts: But of course, as we have alluded to earlier, there's a possibility that they chose roots and tubers for other reasons. They liked not having to do one-time storage. There were rats. As you point out in the paper, very honestly, there's a lot of, what we call confounding factors. But, you've done what I would say is heroic work.

And I want to put that in perspective--again, referring to this meta-question we mentioned briefly, about how science advances--I shouldn't call it science--published academic work advances in our field.

So, you confess that you've been working on this for 17 years. Which is consistent, again, with this previous episode of Adam Mastroianni, where a lot of times, again, I think unbeknownst to normal people, the idea that peer review takes a long time is kind of shocking. You'd think people just, 'I'll take a look at it, verify it, check it.' Yes or no, up or down.

But, no, it takes a long time.

So, some of that 17 years was the paper was rejected. They suggested--

Omer Moav: Well, 10 years was just work, before first submitted. But, then--

Russ Roberts: So, then you submitted it, and they said, 'Well, but you didn't look at this.' So, you did, and they still rejected it. But, eventually, it got published.

So, my question is: At some point you presented this paper at an academic workshop. You went to another university from your own; you started at your own, perhaps, but eventually you started sharing this work. And of course, the people whose work was challenged by your findings, many of them didn't like it. They pushed back. Thomas Kuhn and The Structure of Scientific Revolutions--I think I have this right--basically argued that science advances through death. People whose views are challenged by the new paradigm, until they die off, it's hard to make progress.

Omer Moav: I think that the saying is that the science advances from funeral to funeral.

Russ Roberts: Funeral to funeral, right. So--

Omer Moav: But, unfortunately, when they die, they already have all their intellectual offspring that still protect the old theorem.

Russ Roberts: That's true. It's tricky.

But, your paper was unpublished for long enough that you could have benefited from the death of some of your opponents. We don't need to name any names.

But, my serious question is: A lot of people probably didn't like this paper from the beginning and they still don't like it. What was that like? Were you discouraged? I've known you for a while. I think we've been talking about this paper off and on for probably about 10 years of the 17. What kind of reaction did it get in the academic setting. Not just from referees, but, when you presented it publicly: Did people like it, not like it? Tell me what happened.

Omer Moav: So, I and my coauthors, we presented it in many, many seminars and conferences. Most people really liked it and were actually even enthusiastic about it. Great news.

But, then, here is the problem. And, I actually had a rant on Twitter about that, which was quite--got a lot of attention. I made two comments.

The first one, and now I actually typically ask young economists, 'Could you tell me what is good research?' And, you know, people just give very different answers. The younger generation, 'Good research is a research in which I could really identify a causal effect.' And, I say, 'That's interesting.' I of course completely disagree, because that's not the goal.

And, here is the way I define good research. Good research is research that significantly changed your priors about an important topic.

Of course, if a paper carefully identifies the causal effect in a way you were not aware of it previously, then that could significantly change your priors about an important question. But, you could have a paper that doesn't direct very careful identification, but still the combination of data and logical arguments makes a significant change of one's prior beliefs about an important topic. And that's exactly the paper we have now.

Of course, we don't just show some correlations. We do a very careful empirical exercise with causal identification, and it's very robust. We control for all the confounding--blah, blah, blah. Of course, one could only refute theories; you can never prove a theory.

But, a lot of referees, from mainly, I guess, the identification mafia, were just completely ignoring the big question. That, 'Wow, what a paper. This is so important and interesting,' which is a lot of what other people said. But, they just say, 'Oh, this paper tries to identify the effect of land productivity versus cereals on the emergence of hierarchies.' They ignore completely the logical arguments, the beauty of the argument, the importance of the argument, the originality. And, then, they just have a very long list of concerns.

Now, here's an interesting thing. If you tell someone, 'Look, I have a data set that shows that the effect of X on Y is positive,' and so, maybe it's right, maybe it's not. 'Okay, here is another data set that also shows the same result.' Does that strengthen your argument?

Well, of course, statistically it does, right? No doubt.

But, for many referees, that just makes their list of concerns longer. Well, with a longer list of concerns: of course we reject the paper. So, that was the one type of hostile layer, which is maybe--I don't know if hostile--I would say narrow-minded referees that were against us.

The other was really the hostility. Now, we didn't see many of them in the seminars, because if you're hostile, you typically hide it in a seminar to a large extent. But, an anonymous referee could go full--hide into a paper, hiding behind anonymity.

I think most of the really hostile referees were actually not economists.

So, an editor sees a paper which asks a question or refutes an important theory in political science, would typically feel obliged to send the paper to one or two economists as referees, but also to a political science, or a sociologist, an anthropologist. And, these guys--it's a bad combination because A), they're hostile. B), in many cases, they don't really understand what we are doing.

And so, you see the report, they're not just hostile, they're also silly. In some cases, editors just say, 'Look, I have this very negative report, so--or two negative reports--so I'm rejecting the paper.' Sometimes, unfortunately, they even say, 'I was convinced. Although I had my own reading, I liked the paper, but then this referee convinced me that it's not worth publishing.' And, I read this report, and wow, it's just a silly report. The arguments are flawed.

Anyway, luckily for us, the editor in the JPE, Ali Hortacsu, actually went to a large extent against the referees. One referee stayed hostile and negative throughout the process. The others started [inaudible 00:58:50] and eventually was convinced and became positive. And the paper is published. And I think they do not regret it. I think they're happy with the paper.

Russ Roberts: Well, it's young, we'll see. Just kidding.


Russ Roberts: Let's close with one of the things that I thought about when I was reading this, that I think is--again, it doesn't have a lot of policy implications, but it's part of being a human being, so I'm interested in it.

And, I think back to the interviews that I've done with Rachel Laudan, who is a food historian. And, we've been throwing around the words 'tuber' and 'cassav'a and 'wheat'. These things are really not that friendly to the human digestive system. They're not just things we grow and eat the way we do when we think about a carrot, say. You grow a carrot, pick it up out of the ground. Or if you're buying it at the store, you might rinse it off, you might not. You might peel it, you might not, but you eat it. Cassava, wheat, rice--these things take a lot of preparation to make them suitable for human consumption.

And, one of the things I liked about your paper was it makes you realize that--I don't really know how much we really truly understand about our pre-modern history of hunter-gathering and Dunbar groups of 47 people. I'm agnostic and I don't find it that interesting.

But, when I think about this evolution to agriculture and the rise of the city state--Mesopotamia, Samaria, Egypt--and we start to think about those cultures, they're still affecting us today. Hunter-gatherers, maybe our genes from those days are still in us when we see a tiger. But, those other things are really part of our modern existence, even though we don't think about it very often.

And, when I think about grain and the importance of grain, the storage aspect, the implication it might have had for our evolution of government, and just the whole challenge of subsisting, and the idea of surplus, which is a miracle, crazy.

Anyway, I just like that. I'm just going to say it. You can respond to it, say whatever you want. But, I think it's an important part of our humanity that's worth thinking about.

Omer Moav: I agree. Thanks.

Russ Roberts: My guest today has been Omer Moav. Omer, thanks for being part of EconTalk.

Omer Moav: Thank you very much for having me.