Public lecture by Professor Jeffrey D. Sachs
London School of Economics and Political Science, 27 October 2026
Chair: Professor Sir Tim Besley. Supported by the Huth Initiative for a New Political Economy.
Edited transcript, with endnotes added in editing
Introduction
TIM BESLEY: Good evening, everybody. My name is Tim Besley, and I'm delighted to welcome you to the LSE this evening for Jeff Sachs's lecture, which is supported by the Huth Initiative for a New Political Economy. The initiative brings people together across the LSE community to develop a new economic paradigm for fairer, more sustainable prosperity.
Jeff Sachs needs very little introduction. He is a University Professor and Director of the Center for Sustainable Development at Columbia University, and President of the UN Sustainable Development Solutions Network. As well as making major academic contributions, he has served as special adviser to three United Nations Secretaries-General, and he is the author of numerous books, including The Ages of Globalization: Geography, Technology, and Institutions and The End of Poverty.
The title of Jeff's lecture this evening is "Geography and the Wealth of Nations," a tribute to the fact that it is 250 years since Adam Smith's Wealth of Nations was published. He will speak for around 50 minutes, and then there will be plenty of time for questions, including from our online audience, whom I particularly want to welcome to the event. Jeff, the floor is yours.
[Applause]
The Lecture
JEFFREY SACHS: Thank you, Tim. I love being at LSE. It has always been a high point for me throughout my whole career. I was just reflecting with Professor Richard Layard, one of my heroes in our profession, that this is the 35th anniversary of the Robbins Lectures that I gave here on Poland's transformation back in 1991. That was a grand event for me, and I feel the same this evening. I'm thrilled to be here. Congratulations on this new series, and thank you for including me in it.
As Professor Besley just said, this is the 250th anniversary of The Wealth of Nations. Frankly, I think we should have done a better job celebrating it. I'm sure there were conferences that I don't know about, but there weren't enough. Not enough has been said about that remarkable book.
By the way, for the students: everyone reads a little snippet about Adam Smith, or knows about The Wealth of Nations, or knows that he was the start of classical economics, as Karl Marx labeled it. But my guess is that most of you have not read The Wealth of Nations, because it's an old book. It has no equations. What difference could it possibly make? It is actually incredibly fun to read, and brilliant. It is not just a famous book; it is an astoundingly interesting book. I admit not every chapter, so you don't have to go laboriously chapter by chapter, but it has some grand themes.
It also has economics practiced in the most wonderful way, which is that Smith was thinking in concepts. Of course, he introduced the division of labor as fundamental. He introduced trade as the mechanism of the division of labor. He introduced the idea that specialization is limited by the extent of the market. All rather wonderful ideas. But he also knew the world. He was a real scholar. He had studied world history, he had studied geography, and he had studied the contemporary world he lived in, and it shows. He talked about the price of transport in different places and by different means, very specifically, and then drew major principles from that.
One sentence that galvanized many studies and many articles that I published was his observation that the division of labor begins at the coast and only gradually moves inland, because sea trade is so much less costly than overland trade. So you get coastal populations engaged in trade; trade is the basis of the division of labor; and you can then chart the path of the division of labor spatially.
He also talked about landlocked countries, which became a big theme in my career, because I have advised many landlocked countries. Landlocked countries tend to be difficult places. My wife would say that only desperate places would call me for any kind of help, so almost by definition it was landlocked countries that were desperate enough to go to a crazy professor and ask what they should do. But Smith had actually pointed this out. It took me a while to recognize it. I started advising landlocked countries in Bolivia 41 years ago, and then I read the text and said, "Oh, that's really smart. That's actually quite helpful."
One of the things Smith said is really the theme of this lecture and of four articles that I will post. I hope you will read them. They are long, but I need your comments, because I think they are interesting. It concerns the longue durée of world history, as Fernand Braudel would have called it, the long sweep of world economic history. Smith made a quite fundamental point. He said that the discovery of the sea route from Europe to the Americas, by Christopher Columbus, and of the sea route from Europe to Asia, by Vasco da Gama, which came within six years of each other, in 1492 and 1498, were the two most significant events in the history of mankind.
What a weird statement. And how brilliant and incisive. We will see a piece of the quote in a moment. He wrote that these were the most significant events in the history of mankind because they united humanity. They reconnected the Old World and the New World, which had been separated for the previous 10,000 or 12,000 years. After the end of the Ice Age, the sea level rose by many tens of meters, and the land corridor that connected Asia with the Americas, called Beringia, was submerged. That corridor had been the route by which the Native Americans reached the Americas long before Columbus arrived. For 12,000 years, the Old World and the New World were basically separated, and Columbus inadvertently reconnected them.
Smith says that this is the most significant event in the history of mankind, and that it should help everybody. But in fact it immiserated the native populations of the Americas and of Asia, of the West Indies and the East Indies, as he called them. He then explains why, though he doesn't get it exactly right, as I will discuss in a moment. Then he says that someday those native populations will rise in force and rebalance the world. He says that the most likely way this will come about is through trade itself, through the flow of know-how. He doesn't use our words, technological diffusion, but he says it will come through the flow of knowledge, and knowledge is carried by trade. So someday international trade will rebalance the world and lead to an equality of power among the regions of the world that will stop the abuses of the European empires.
This is unbelievably smart. And what I find unbelievably interesting is that this is exactly the world we are in right now. The world has rebalanced in front of our eyes, in this generation. It really began after 1950, with the end of the European imperial age, but we especially feel it after the year 2000. I would say that for the last 25 years we have been in a multipolar world. And not just a multipolar world: by the measure of the IMF, the ultimate arbiter, China's economy is bigger than that of the United States. That is a fundamental change in the balance of power. The share of Europe and the United States in the world, the so-called West, which was the dominant part of the world, is by far no longer dominant. Asia has returned to center stage. I would say it is now half of the world economy.
So there are two things about Smith that I want to stop on before I turn to some data. First, he predicted this. He didn't give a timeline, and he didn't talk about GDP numbers, because that concept did not exist and would not exist for roughly another 150 years, until we could measure these things in a meaningful quantitative sense. But he did say there would be a rebalancing of the world.
Second, he looked forward to it. That is an incredible tribute to the Scottish Enlightenment, and to Adam Smith as a very decent human being. He said that what the world needs is balance, in which every part of the world thrives. That is a great concept for economics; I think it is the most important fundamental concept for us. It is the reason why we should celebrate China's rise, not bemoan it. Not say, "Oh, how horrible," but say, "My God, this is phenomenal: nearly 800 million people lifted from extreme poverty in the past four decades. Great."
Instead, of course, we bemoan it. It's horrible. We have to get ready for war. We have to build up our military strength. These people don't read Adam Smith, they don't read Aristotle, and they don't have their heads screwed on right. We call them our political leaders. They are making a mess of the world because they don't understand economics, and they don't understand why the common good is good, beyond their own small vantage point.
One more point. Smith's idea of a rebalancing did not work for about 150 years, from the time Smith wrote until the middle of the 20th century. It didn't work because the natural economic forces that would have produced it were blocked by European imperialism, and by Japanese imperialism with respect to East Asia, especially China. The imperial age was an age of divergence, in which the powerful became richer and more powerful, and the weaker became subservient and suffered extraction, abuse, in some cases enslavement, and in some cases famine and utter disaster at the hands of the imperialists.
What makes the current age conform to what Smith said is that the end of imperialism, which came at the end of World War II, basically after two European civil wars, opened the way for sovereignty in the rest of the world. Sovereignty opened the way for catching up and for narrowing the gaps that had arisen during the high imperial age. That is what led to the period of convergence we are in right now, which Smith anticipated 250 years ago.
Convergence is now mainstream growth theory. My colleague at Harvard, Robert Barro, wrote beautifully about it, and I think his insights about conditional convergence are extremely important. They had a big influence on my understanding of events. But convergence was contingent on a world order in which countries could pursue their own destiny, and that came only after 1950.
All of this means for me that we have a big task in understanding the shape of the world. How did it come to be? How are we now in an age of convergence? What happened that led to the massive age of divergence? Is the return of Asia to center stage really a return, or is it something new? Is it something we could have anticipated and should have anticipated? Is it what Smith anticipated? Those are the questions that motivated the four papers behind the slides I am going to show you. I can't go into detail on anything, because time is very limited, but I want to touch on a few high points with you.
Through Smith, and through my own lucky experience of advising landlocked countries, countries high in the mountains, and countries burdened by malaria, I have felt viscerally for a long time that physical geography is absolutely fundamental to understanding the shape of the world economy and of world history. I assert that to be true, and I praise Adam Smith for knowing it in certain respects.
He did not understand the role of pathogens in history, because it would be another 100 years before germ theory was established science, with Koch and Pasteur. So he did not understand what led to the misery of the West Indies. The main cause was Old World pathogens carried by the Europeans, which hit a virgin population that had never seen most of the diseases of the Old World. Those pathogens did not even exist in that form 10,000 or 12,000 years ago, when the ancestors of the Native Americans came from Asia across Beringia. So the Native Americans met smallpox and many other diseases for the first time, and it destroyed their population. Around 90 or 95 percent of the population died between 1500 and 1600, some by war, some by suppression, but many by pathogens.
Pathogens have shaped history fundamentally. Rivers have shaped history, climate has shaped history, and mountains have shaped history. The role of geography in understanding these events is enormous, and that is really what I want to share with you in some broad outlines.
As I said, my favorite sentences in The Wealth of Nations are these: "The discovery of America, and that of a passage to the East Indies by the Cape of Good Hope, are the two greatest and most important events recorded in the history of mankind. … By uniting, in some measure, the most distant parts of the world, … their general tendency would seem to be beneficial." Then he says that at the particular time when these discoveries were made, the superiority of force happened to be so great on the side of the Europeans that they were enabled to commit with impunity every sort of injustice in those remote countries. And hereafter, perhaps, the natives of those countries may grow stronger, or those of Europe may grow weaker, and the world will be rebalanced.
What I want to describe is how to understand these events in a longer sweep of history. The history in these papers covers 2,000 years for most of it, and 3,000 years for part of it. We live in a beautiful age, because we now have data, imperfect but extremely interesting, on world populations at every century benchmark for the last 2,500 years. We have political boundaries that have been assembled for the last 2,500 years. We have estimates of land use, of city populations, and of farming populations and types of farming for 2,000 years. Much of this was developed in the Netherlands, building on projects that Angus Maddison started decades ago, which continue to be extended, now on the basis of geographic information systems. What I have done is put all of this on a common grid: the politics, the land use, the climate zones, the physical geography, the population estimates, the urban extents, and the imperial extents, to see what it can tell us about the broad sweep.
The main points are the following. The food system was the great shaper of the world economy for thousands of years. In fact, I would say it was the defining element of the world economy until around 1800. The only fundamental change from the principle that the food system defines the economy came in the 20th century, with the invention of synthetic nitrogen fertilizer. This was the first time in world history that you could break the fundamental constraint of growing crops, which is to have the right nutrient in the right place at the right time. Fertilizer changed everything. That is a new phenomenon. The Haber-Bosch process for nitrogen fertilizer was completed in 1913, and its diffusion took place throughout the 20th century. It remains incomplete in Africa to this day, where fertilizer is little used because of poverty and the lack of economic systems, and so crop yields are desperately low. But for the world as a whole, there was no fertilizer, and especially no synthetic nitrogen fertilizer, for almost all of our history.
So, as I will emphasize, and strangely enough although it has not been much of a feature of economic history, the nitrogen constraint is probably the single most important constraint that defined where people lived, how large populations were, how people farmed, where cities were, and where political systems were. Strange, but quite notable.
Second, Malthus was basically wrong. The theory we attribute to Malthus is that there is a land constraint; that if you ease the land constraint through a productivity increase you get a population increase; and that this drives living standards back down until fertility and mortality balance again. That is basically not right. What limited human populations for almost all of history was not land. The simple thing to note is that world population was about 500 million in 1500 and remained below 1 billion until the early 19th century, so we were using a small part of the arable land throughout human history. Land was never really the constraint. What was the constraint was survival, mortality. Interestingly, mortality, as best we can judge, was not limited by food. It was basically pathogen-driven. There were constant plagues and other epidemics that routed populations every few hundred years. Eventually those pathogens evolved, and those epidemics basically went away. Not because we got richer, but because there was enough time and genetic drift in the pathogens. Those pathogens were, in a way, human-created, because most of our diseases are somehow related to agriculture, to animal reservoirs, to zoonotic events thousands of years ago. Basically, we adapted to the pathogen set, and that broke the population constraint. So I argue that the issue is food systems, but not in the Malthusian sense. What held back population was that it kept getting wiped out every 100, 200 or 300 years in large parts of the world.
Third, population densities already differed radically around the world 2,000 years ago. Why? Nitrogen. Weird. Where could you grow food on a densely settled basis? It turns out, not in many places: only the temperate zones, or places with alluvial soils, where flooding replenishes the nutrients, like the Nile, the Indus, the Yellow River, or the Tigris and Euphrates. There you had very thick population densities because of the constant alluvial replenishment of nitrogen and other soil nutrients.
Or something extremely important and interesting: paddy rice replenishes its own nitrogen. It is its own fertilizer. Paddy rice, flooded rice, which for most of human history was essentially unique to South and East Asia, has cyanobacteria associated with it that fix nitrogen. The paddy is therefore a fertilizer machine, and it allows annual cropping of rice. Where you could grow rice in flooded paddies, you had high population densities. So, for 2,000 years, all the evidence is that India and China were packed with people. Europe was in the middle. Africa had very low densities, and the Americas very low densities. That, I argue, is because of different food systems.
Now, high population density creates states. Where there were organized large states is where there were large populations. The quintessential case is China. China has had the largest continuous organized state in human history. In fact, it is the only place that for 2,000 years was almost always a unified large state, typically with about 20 percent of the world population in it. No other part of the world has anything like that record. Second is India, which has had long periods of unity: under the Delhi Sultanate, under the Mughals, under the British Empire, and in the current Indian polity. But it has nothing like China's record: unity as a large state for about three-quarters of the past 2,250 years, based on a very dense population and a unity that did not come to other parts of the world.
Europe is the other place of relatively high population density. Not like the riverine systems of China or India, but relatively high, because Europe also solved the nitrogen problem in a distinctive way, through mixed farming, with animals whose excreta were used to fertilize the fields. That is also quite a distinctive farm system, not available in the Americas or in Africa, for very specific reasons.
Europe did not unify politically in the same way after the collapse of the Western Roman Empire in 476. So, what is interesting is that you have two cases of relatively high population density: high in East Asia and relatively high in Europe. Europe fragmented in 476 and never unified again. East Asia unified in 221 BC, broke apart for about 300 years, from roughly 200 to 500, and then has been unified from about 500 until today, with very short breaks. I try to argue that this is quite a significant feature.
The last point I would make is that you have large states in Asia, especially China and India, and many states in Europe: hundreds of individual polities, of course, because you had dukedoms, principalities, and all the different early proto-nation-states of Europe, generally fighting with each other for basically 1,500 years until today. Unfortunately, Europe seems to like to fight and does not seem to have an idea of peace as a strategy, only war as a strategy.
But Europe ended up dominating the world for about 150 years, from around 1800 to 1950. The Napoleonic Wars had to end first, and then the 19th century was Britain's century. Britain created the largest empire in world history: 29 million square kilometers and about a quarter of the world population. Nothing like it had ever been seen before, and nothing like it will ever be seen again, I believe. But it lasted quite a short time, roughly 130 years, and then it ended.
By the way, there is a wonderful quotation from Joseph Chamberlain, one of the great imperialists at the end of the 19th century, who declared that the British race was "the greatest of the governing races that the world has ever seen." Who could compete with Britain? That is basically what Americans say right now, which means that the end is very near. That naiveté is something that is true throughout history. It is called hubris: the pride before the fall.
So, we have this period of about 150 years when Europe dominated, and that of course requires an explanation. For a long time, the explanation given was Europe's superiority, in one of many different ways depending on the proponent: it was Christian, or it was white, or it had the right civilization, or it was a genetically superior race. Unfortunately, even the wonderful humanist Charles Darwin wrote in The Descent of Man in 1871 that "the civilised races of man will almost certainly exterminate, and replace, the savage races throughout the world," and he included Africans among them. Charles Darwin was a great scientist and a very wonderful person, completely wrong about this, but reflective of the dominant view at the end of the 19th century.
What is interesting, of course, is that the African population will rise in this century, from around 9 percent of the world population in 1950 to around 35 percent by 2100. The reason is nitrogen. Until the 20th century, Africa could not sustain intensive agriculture. With fertilizer, Africa can sustain a vastly larger population, and that is the population it is on its way to sustaining.
All of this leads to my last point, which is that we are back in a multipolar world. The West should give up any idea that its economic and technological superiority means that it rules the rest of the world, because that is completely passé. The biggest geopolitical challenge in this world is for the United States to calm down and get its head on straight. But I wish the British government would also calm down a little. There is too much Russophobia, too much warmongering. We'll see what tomorrow's budget brings, but if it brings a call for more military spending, please reject it. It's absurd.
[Applause]
This is the last thing in the world that anyone needs. It is much cheaper to talk and work out mutual security than to have this escalation toward war.
I have probably used all my time, but I want to show you a couple of things. Ten more minutes? Okay. There is actually interesting material to show.
This is modeled data on the food systems used in 1500. The red is paddy rice; you can see where paddy rice is. These are rough estimates, and the papers have a full methodology explaining the derivations and the interpretation of the data. The brown is what is called swidden agriculture, or slash-and-burn agriculture. It supports very low population density.
Here is why. When you farm, you grow food. The food contains nitrogen; that's the protein. You eat the protein, and you excrete it not in your field but at your home. The nitrogen doesn't get back to the field, so you have depleted the field's nitrogen. That's the basic problem of nitrogen: you extract nitrogen, you eat it someplace else, and you excrete most of the nitrogen you eat, but not in the fields. The nitrogen you excrete volatilizes, turning back into atmospheric nitrogen, N2, rather than the forms that plants can use, such as nitrate or other reactive molecules the plants can absorb. That's the nitrogen problem. If you want to farm continuously, you have to put nitrogen back into the soil.
One way to do that is to take human waste and put it back on the soil. In East Asia, in some places in Japan, that was done; it's called night soil. It was also done in places in China. It was not done in most places in human history. It required a very highly organized activity of collecting the excreta and bringing it back to the fields, and it took a densely settled population to justify it. So most of the time, that's not how the nitrogen problem was solved.
How else do you solve it? One way is to grow food for a few years until the nitrogen in the soil is depleted and then leave the land for 20 years. That's the normal way, because nature then refixes the nitrogen, biologically and through lightning, and you get reactive nitrogen in the soil again. But it takes 20 years to replenish, and that's what swidden or slash-and-burn agriculture is. You can't crop a place continuously, so you need a huge area: you crop a place for a couple of years and then move somewhere else. The equilibrium population density is very low. That is one solution. All of the Americas had that solution, and most of Africa had it. Until the 20th century it was really the only practical solution in much of the tropics, because in the tropics you could not use the other solutions.
What is another solution? You have a farm and a large grazing area, and your animals graze. They pick up nitrogen from the distant pasture, not from where you're cropping. You bring them back into the fold, they excrete the nitrogen, you collect it, and you put it on the soil. That is the European mixed farming system, a mixed system of animals and humans. For it to work you need many things. First, you need the animals, and if the animals can't survive because of trypanosomiasis and other animal diseases, as is especially true in Africa, you can't keep livestock. You also need a dry season or a cold season. You gather the animals in the cold season, collect their manure, and put it on the fields. The cold stops the nitrogen from volatilizing back into the air. You need a way to make sure that the nitrogen doesn't leach into the groundwater or escape back into the air, and that usually requires cold. So mixed farming with animals is generally temperate-zone farming. That's the second way.
A third way is flooding. Alluvial flooding, river flooding, brings nutrients from the upper reaches of the river. The classic case is the Nile, which flooded every year until the Aswan Dam was built. It defined Egyptian civilization for 5,000 years. It brought nitrogen and other nutrients across the Nile valley, including the Nile Delta, and it supported a huge population. Indeed, the Nile Delta fed Rome. Grain was literally shipped from Egypt to feed Rome. One of the reasons Rome fell is that as the empire expanded, the grain from Egypt was diverted to Constantinople, because Egypt fed Constantinople. Rome then depended on grain supplies further west in North Africa, and when the Vandals captured those areas, Rome fell, because in the end it didn't even have a food supply left. So alluvial agriculture is another way of supporting a high population density, because the floods bring the nitrogen.
And then, as I said, paddy rice is the genius crop, because it fixes its own nitrogen. It is incredibly labor-intensive, by the way, so you don't have an easy life. You have a huge population working year-round in the rice fields. But the density is enormous: 10, 20, even 100 times higher than under swidden, and perhaps 10 times higher than in a typical mixed-farming environment.
In this study I track all of these systems, and I use estimates of nitrogen uptake by the crops and of nitrogen replenishment to estimate where populations would live. We find an incredible concentration of population in the world. Ten percent of the habitable land area routinely held more than 50 percent of the population. That was South Asia and East Asia, with the huge populations of China and India. It has been true for 2,000 years. It is a farm-system effect: a rice effect and an alluvial-agriculture effect more than anything else. It is not a political effect, and it is not geopolitics. It is simply where you could grow food at very high population densities. And this is where cities developed. Cities developed where population density was high enough to feed non-agricultural populations. Generally, our agricultural technology over the last 10,000 years has been barely enough to feed humanity, and in bad periods many people died. The surplus was perhaps 5 to 10 percent, and that surplus is what created cities, whether through tribute, extraction, or even market forces. You need an agricultural surplus to have a city. Urbanization everywhere in the world was 10 percent or less for almost all of human history. It started to rise to 20 or 30 percent only around 1700 and 1800, with improvements in agriculture in the Netherlands and in England, and most of the world remained 5 to 10 percent urban because the surplus was very small.
But where were the cities? No swidden system could support a city. Population densities were far too low. You couldn't collect taxes, and you couldn't base a city on a very diffuse population. So, the cities of the world are incredibly concentrated. It may be hard for you to see, but the dots show where the world's largest cities were, all in one band that historians have come to call the lucky latitudes. They never really defined why those latitudes are lucky. They are lucky because they support a high population density, and nitrogen is actually the key to that story. There were almost no large cities elsewhere. These are the 48 cities that had populations of 100,000 or more in 1500.
This is the miracle of our data right now. By the way, I didn't make any of these data; I just put them all on a common grid. What do we know about population size, about where populations were, about city boundaries? It turns out the large cities all sit on mixed farming or on alluvial or flooded farming, alluvial meaning river-fed and flooded meaning, basically, rice. That's where the big cities of the world are.
That is also where the empires of the world were. All empires were based on sustained agriculture, which produced dense populations. Even the Mongol Empire, which came from the steppe, a region of very low population density and a tiny population, conquered the largest contiguous land empire in history, about 27 million square kilometers. But the actual Mongol Empire was settled agriculture ruled over by a small nomadic conquering class. It exploded in 1206, when Genghis Khan united the tribes, and it lasted only about 150 years. But the empire was where the settled populations were, because you need populations to extract from.
This map shows where the states were. We now have not only GIS data on cities but also imperial maps at regular intervals going back 2,000 years, in a project called Cliopatria, from "Clio," the muse of history, and "patria." It is a wonderful GIS-coded database.
The final point I want to make is that you have settled populations across that band, but you have unity in East Asia and fragmentation in the west, in Europe. That is an interesting question in and of itself, and I offer some ideas about it in one of these four papers. Here is my basic point. China is a box. In the north are the drylands. In the south is the border of tropical rainforest and tropical disease with Southeast Asia, especially Vietnam and today's Myanmar. The east of the box is the Pacific Ocean, and the west is the Himalayas. That box has defined China for 2,200 years, with very little change, though there are some footnotes to that.
Second, most of China lies on two rivers that run east-west: the Yellow River in the north and the Yangtze to the south. Between 605 and 610, the Grand Canal linked the two rivers, and China was unified. So you have a box, and you have the unity of most of the population.
Also, in 221 BC, the Qin dynasty ingeniously created a unified logographic script, Chinese characters, that could be read across languages. That is hard for us to understand, I have to say. I have tried to understand it more precisely for decades, and I'm not sure I really do. But whether you speak Fukienese or Cantonese or Shanghainese, which are called dialects but are actually separate languages, the script is the same, and it was developed already in 221 BC. It also enabled a uniform examination system for a unified state. Everybody could read one written language and study one canon, basically the Confucian canon since 136 BC, and that also created unity.
India is a little different, because the geography of the north and the south of India is quite different. The population origins are also quite different, because the northern Indian populations probably came from around Iran and the steppe regions. In any event, India was semi-unified, and Europe was fragmented. It fragmented in 476 and had none of the features that could lead to long-term unity.
A final point, and then I'll stop, because I know the time is up. For 2,000 years Asia has had 60 to 70 percent of the world population, for the reasons I have given: China and India together usually between 35 and 50 percent of the world population, and the rest of Asia at lower density, for a total for Asia usually of 60 to 70 percent. For almost all of history, income levels per person were roughly equal, because every place was essentially agrarian, mostly rural, mostly eking out an existence, and not very different until the 19th century, especially the Industrial Revolution. So according to the Maddison data, which I used for this study, the population share and the share of world output were basically the same for as far back as one can gather. I think Maddison was not wrong in estimating basic equality of GDP per capita across the world.
That changed late. As you know, there is a big debate about whether it changed in 1700 or in 1800; this is the Pomeranz debate. How recent is the divergence, and what accounts for it? To my mind, two things can be said. First, the divergence came late: even 1700 is late. Second, the interesting point is why it persisted. To my mind, it persisted because of power, not because of economics. There would otherwise have been a rapid diffusion of the new technologies, because the Ottoman Empire was not stagnant, the Egyptian state was not stagnant in ideas, and China was not stagnant and paralyzed. But these places were prevented from adopting and adapting technologies by imperialism. That is my shorthand interpretation. Convergence was restored only with independence and the end of the imperial period, as I said.
What this means is that up until 1820, Asia's share of world output was 60 percent. It fell to around 19 percent in 1950, after what the Chinese call the century of humiliation and after India suffered basically 200 years of imperial domination, which did not treat India well. That was the low point. Independence came in 1947 for India and in 1949 for the People's Republic of China. Now we are back to 50 percent of world output being in Asia. I call it the return of Asia to center stage, and I think that what we are experiencing in this period is completely normal and completely in line with what Adam Smith brilliantly said.
I want to show you one more point that is interesting. This is the centroid of the world economy and of world population. You can calculate the center of gravity using geodesic distance, or economic distance, in a variety of ways, and it is quite interesting to do. The center of gravity of the world population was always in Asia, naturally, because that is where the world population was centered. But in the 19th century, the economic center of gravity moved from here to there. In 1950 the center of the world economy was literally in Britain. It probably felt like it was a few blocks from here, maybe right here. The point is that this was really odd from the point of view of long-term world history.
Now we are on the way back. This was 1950, and now we are somewhere around here, with the center of gravity of the economy coming back toward the center of Asia. Using standard convergence equations, the curve swings down here, because Africa becomes a much larger part of the world economy.
Interestingly, you can calculate the distance between the population center of gravity and the economic center of gravity. If output per capita is equal everywhere, they are of course the same place, and that is what you find historically: no distance between them. Then suddenly, by 1950, there were about 6,750 kilometers between where the population center of the world was and where the economic center of the world was. Now we are coming back to what I think is normal again: over time, there will be relatively equal levels of income where people live. As long as there is peace and independence, there will be convergence.
One implication, by the way, is that Africa will be a very large part of the world economy by the middle of this century and later in the 21st century, because Africa, as I said, will have about a third of the world population. What makes that possible, again, is that we no longer have the nitrogen constraint we had before. Plenty of nitrogen can be made by the Haber-Bosch process, and now it can be made in a green way as well. That is going to change world history. Thank you very much.
[Applause] ## Questions and Answers
TIM BESLEY: Thank you very much, Jeff. I'm going to go straight to the floor and take questions in batches of three. I'll ask you to be super brief. I don't want statements; I want short, punchy questions. Then we'll go back to Jeff, and I will also take some questions from the online audience. Please don't ask your question until the roving mic reaches you. The first hand I saw was down at the front.
AUDIENCE MEMBER (NIGEL JEFFREY, KING'S COLLEGE LONDON): Thank you very much. You've emphasized agricultural production. What about consumption, and the relative efficiency of plant-based diets compared with meat-based diets, and the impact that could have had on the populations of the East?
TIM BESLEY: A question about consumption. The next question, here at the front, please.
AUDIENCE MEMBER: Thank you. Good to see you again; we last met at Harvard in 1999. My question relates to Mark Carney, who also went to Harvard. He has proposed an alliance of middle powers, anchored on shared values and technology. If you were to apply your analysis of nitrogen-based food systems to assess which countries from Asia and Africa should be included, which would you recommend, and why?
TIM BESLEY: And then a question at the back. If people are brief, we'll get a lot of questions in.
AUDIENCE MEMBER (FERNANDO MORALES DE LA CRUZ): Jeffrey, we spoke in the days of Skype, before Zoom, about coffee. I dare to ask you because you were so passionate about the Sustainable Development Goals and involved in coffee. Do you really believe that the coffee industry will change one day soon, so that people living in the coffee lands can have three meals a day and can actually protect the environment? If I have a fair-trade coffee at LSE, less than 1 percent goes back to the farmers. That's not fair trade. Thank you.
TIM BESLEY: Three questions there, Jeff.
JEFFREY SACHS: Great. On consumption and production: at least across the span of history, from what I have been able to discern from the secondary literature, there is not a big difference in caloric consumption across the world. The differences are not primarily due to food losses, harvest losses, or different levels of consumption of proteins and calories. For most of human history, from what I can see, people lived on about 2,200 calories a day. They obtained them according to the endemic species, the animals that were present, and the farm system that could be sustained. But I don't see anything decisive myself on the side of per capita consumption that accounts for these differences, though I will go back and examine it. It is also generally taken to be the case that there were no significant differences in output per person. Of course, in the Maddison data what is being measured is mostly crop output, because these economies were overwhelmingly agricultural. So I don't think the differences come from the consumption side, but I will see whether there is any more mileage I can find on that.
On the middle-power alliance: first, Mark Carney was one of our best students in the Harvard economics department in the 1980s. We're very proud of him, and proud of him for standing up to Mr. Trump, which is an important thing to do.
But a few things. The world is going to be heavily shaped by a few great powers. There will not be one hegemon. The United States wanted to be the hegemon. It turned out that things were not the way America, or America's leaders, thought. China rudely stepped forward and said, "Excuse me, we're here too. We're bigger than you, and we're not going away." That was very rude of China, by the way, because nobody gave China permission to do that, least of all America. China was supposed to assemble our phones and be quiet.
But China has reached its peak population, and its population will decline significantly in the next 75 years. According to the UN forecast, China's population will fall far below a billion people; in the most recent revision, to about 630 million by 2100, and India at that point will have more than twice the population of China. China will not be the world's hegemon. I would also stress that China has no interest, tradition or desire to be the world hegemon. China has never wanted overseas empires. It never tried to build them, and it never tried to colonize overseas.
I like the fact that China never once in 2,000 years invaded Japan. Not once. Can you imagine? Britain and France were at it every month for about a thousand years across the Channel. It never dawned on the Chinese to do anything other than have a tribute exchange. Of course, they wanted the Japanese to bow a little lower, maybe even to kowtow, but generally what China gave back to Japan was worth more than anything it tried to extract. So the so-called tributary system, or Confucian system, was not an extractive system, and China never tried to invade its neighbors. It is fascinating and really important to look at this closely.
The Mongols, by the way, tried twice when they ruled China, in 1274 and 1281, failing both times because of typhoons, the so-called kamikaze winds of Japanese tradition. But that was the Mongols, and they didn't try again after 1281. China never tried. Japan, of course, invaded China pretty much nonstop after 1894. I would like the Japanese to calm down, stop saying that China is a threat, maybe even apologize for what was a very, very terrible period for China, avoid a military buildup, and tell America, "Take your soldiers home. We don't need them. We can have a perfectly safe relationship with China. Thank you very much." That would be my own advice to Japan. I think it would bring a lot of prosperity to Japan, because Japan has a lot that it could contribute to China, and China has a lot that it could do together with Japan. But the point is that China never tried.
Back to the question about the big powers. We have the United States, Russia, China, India, and possibly someday Europe, if Europe would actually behave as one rather than as 27. I'd even like it to be 28, frankly, and I think it would be good for the 28th, or the first, or whatever order you want to call it, to return to a good partnership. In any event, we have four major powers right now and nine nuclear powers. The middle-income countries can't undo the vast difference in power. What they can do is help establish and deepen norms of behavior.
I would like the world to tell Donald Trump, "Stop it. You're not a thug. We don't behave this way. You can't stand at the well of the General Assembly and say you're deciding whether to annihilate Iran or to make it a great country." Either you're nuts, or someone should sit down with you and have a chat, or take you away, or something. But we should not accept this as a norm. By the way, when Donald Trump said that he was thinking about annihilating Iran after our midterms, which European powers said, "Excuse me, no"? At most one, Spain, and as far as I know no others. That is incredible. That is really incredible.
So what I like very much about what Mark Carney is doing is that he is telling the truth. The biggest shortfall in the world right now is that people are afraid and they don't tell the truth. That is our biggest problem. Our biggest problem is not Russia, by the way, and it is not China. Our biggest problem is the truth, which is that we should stay out of each other's faces, avoid each other's red lines, and stop talking about war coming. I understand British politicians are saying that you need to stock up on water and food. Are they out of their minds? No, honestly, have them call me. I will talk to them.
[Applause]
I call it, by the way, the phantom empire syndrome. The empire is gone, but they still feel it every day. It's time to stop feeling the empire and get a grip on reality. We don't need a war with anybody. That's the main point.
Let me go back to coffee, to return to economics. What is going to happen in agriculture in general, including in coffee, is that the number of people working in agriculture is going to shrink tremendously, and their incomes will converge to the incomes of non-agricultural workers. That has happened in the United States, in Europe broadly speaking, and in Japan, and it is happening in China. Agriculture becomes mechanized. Coffee of course has its own specific set of issues. But in the United States, 1 percent of the workforce feeds the other 99 percent, plus a significant part of the rest of the world. You just don't need many farmers anymore, and that is the way the world will go. Colin Clark pointed this out in 1940, and he was right then, 85 years ago, and it continues to be the right answer now.
If we work at all, which is the question Keynes rightly asked in 1930, we will work in services, because there will be no jobs in agriculture, no jobs in mining, and basically no jobs in manufacturing either. I have recently been touring factories in China, manufacturing plants, and there are no workers there. So if you want the jobs to come back from China, forget it. They don't have jobs in manufacturing. These are what they now call dark factories. You don't even have to turn on the lights, because they are all robotic, AI-driven, and extraordinarily efficient. Of course I'm exaggerating a bit, but this is really the direction. We will do services. We'll talk to each other. We'll have coffee together for many more hours of the day. It will be quite wonderful, I promise. And the robots will actually harvest much of the crop in the end, and that will be fine.
When it comes to the specifics of coffee, because we have worked on this and talked about it together, the idea of a specific coffee fund, financed by the main roasters and the main global companies, is step by step getting onto the agenda. I was at FAO last week, where this was unveiled by Andrea Illy, who produces some wonderful coffee. Now the task is to get the big companies to put funds into it. What is needed is sustainability, because drought and climate stress are a tremendous challenge right now. That is also why coffee prices have soared recently: Brazil has lost much of its crop, and that will intensify in the future. So there is a lot that is specific to any crop, to the climate effects and the environmental effects, and to what to do. But broadly speaking, in terms of jobs and the future of employment, we will be able to grow enough food with very, very few farmers. We will have largely urban societies and largely service economies, and manufacturing and mining, which is already being done autonomously in many major regions, will be fundamentally altered by technology.
TIM BESLEY: Now, Jeff, my understanding is that you have another engagement, which means you have to leave approximately now.
JEFFREY SACHS: No, I have a bit more time. Oops, my watch died. No batteries left.
TIM BESLEY: Why don't we take one more round? We'll go to the online audience first. Nikki, you have a question from the online audience.
ONLINE MODERATOR (NIKKI): Yes. One question: you mentioned that the economic centers will move toward the population centers in Asia. Geography aside, Asia is also facing strong demographic pressures on birth rates and so on, especially China. How will that affect your analysis of the future of the global political economy? This is from a student at LSE.
TIM BESLEY: I'll take someone from the back, right at the end of the row there. Please be brief.
AUDIENCE MEMBER: Thank you, Jeff, for your comments. I'm really a big fan. In your articles, why is colonialism only an undertone in your findings, and how do you address neocolonialism? Agriculture is very big in Africa and in Asia, but companies use neocolonial, exploitative methods in Africa. How do you address that in your articles? Thank you.
TIM BESLEY: And I'll come to the front here.
AUDIENCE MEMBER: Thank you, and thanks, Jeff, for a wonderful world history through the lens of geography. I want to connect with your last comments on technology and innovation, because you didn't really mention technology in your account of world history, except at the point where pathogens ceased to be the constraint on mortality. It seems to me hard to avoid technology, at least for the last 300 years, and there seems to be an ongoing interaction between the forces you have emphasized and technological development. When we use your perspective to think about the future, which you seem to want to do, how should we think about the joint dynamics of the natural, geographical forces and innovation as it goes on?
TIM BESLEY: With huge apologies, these will be the last questions. I know there are many more. Jeff, if you could wrap up.
JEFFREY SACHS: I will wrap up by trying to link the three together: political economy, neocolonialism and governance, and technological development.
I believe the biggest risk we face is conflict and mass disaster, because we seem not to understand how threatening that is and how close we are to it. My country's government, the United States government, does not behave properly, and it doesn't understand the world properly. I would say that Europe is having similar neurotic reactions. Basically, the United States and Europe are still living in a world of Western privilege and Western predominance. That world is over. The biggest risk, I feel, is a divergence between the world as it really is right now, a literate, urban world everywhere, where the differences are not so great and where a middle class is building everywhere, and the idea that the United States or the West still somehow runs the show. It doesn't, and that idea can get us into grave trouble.
For example, the so-called West can wake up one day and say, "Why don't we just bomb the hell out of Iran?" That is what they did, totally arbitrarily, illegally, crudely and dangerously, on February 28th of this year. It is the most senseless, reckless war imaginable. The reason for the war was that they thought they would win it in 12 hours. They're idiots, I'm sorry. The people in my government don't know anything. They had no idea that what they imagined as a country of people in turbans was actually a quite sophisticated society of more than 90 million people that did not want to be run by the United States.
So that is where divergence comes in: the idea that you run the world when you don't actually run the world. And when you think you run the world, everything becomes a double standard. We can do what we want because we're good, and if you do the same thing, you're evil. We're good, you're evil. It's simple. And that is what gets us into escalating conflicts.
So I view our biggest risk as stepping into some total disaster sometime soon, and we have the tools to do it. Nuclear arms are enough to end the world. It takes about 72 minutes. I would recommend reading Annie Jacobsen's 2024 book, Nuclear War: A Scenario. It will leave you in a cold sweat, as it should. In her scenario, it is 72 minutes to the end of the world, and it is quite accurate and very well researched.
Biotechnology is another way. I am of the view that COVID was created in a laboratory, most likely at the University of North Carolina, as part of our so-called biodefense work in the United States, and it got out. Oops. And nobody wants to look at the lab records, by the way, because why would we? [Inaudible.] That's a conspiracy theory. I say open the books, and we'll see. In any event, even if we didn't create COVID, it is not hard to do now. It is not hard to create pathogens and bring them to life.
The third, of course, is AI, because AI can basically hack any connected system, and everything is connected. It can hack your bank accounts, your water supply, your utilities. And it doesn't have to be an Anthropic agent that escapes its sandbox. It can be some nasty son of a … that escapes its sandbox. So we are in a period when the tools are extremely powerful and very dangerous. We happen to have the worst governance in United States history, and that's saying a lot, by the way, because we've had real doozies before. But this guy is really exceptional, as he knows. A genius of destruction. So this is our biggest problem.
The reason I say all of this is that if we avoid all of it, there is actually great good news. That's the irony. We are in a technological age of wonders. That is the bad side and also the good side: all the problems can be solved. Extreme poverty has gone down decisively in this world. In 1990, extreme poverty affected more than 40 percent of the world population. Now it is about 10 percent. Of course there are many people who are poor but not living in extreme poverty, and extreme poverty could easily be ended now, because the tools are even better than 20 or 25 years ago. Similarly, we know we can decarbonize the energy system, and we know we can do what is necessary to avoid the worst of anthropogenic climate change. If we can get our heads on straight, and if tomorrow the Chancellor does not release a budget for more military spending but says, "Let's have some sustainable development," we would be on the right course. All of these issues can be tremendously relieved.
So in political economy, we will be in a truly multipolar world. Not a China world, not a Western-led world, not a US-led world, not an India-led world, but a multipolar world. Great. That is the world Adam Smith envisioned back in 1776.
As for neocolonialism, which is very real right now: a few agricultural companies, mainly American, dominate the world market, but those are American privileges that can easily be ended. What I recommend for Africa is union, the African Union, and Africa-wide standards. By the way, it was an absolute point of American policy for 80 years to ensure that there would be no Arab unity and no African unity, because the idea of American primacy is to make sure there is no unity in the rest of the world, so that we remain the primary power. We learned that from the British, by the way. It is a well-tested strategy.
And technological development is in a golden age right now. It is absolutely incredible what can be done. Demis Hassabis is a genius. He enabled the figuring out of more than 200 million protein structures, and he is not even a chemist. He is just very good at deep neural networks, he figured out how to do this, and he shared the Nobel Prize in Chemistry for it. So I think we are in an astounding, positive age if we want to be, and that our risks are ourselves.
Basically, we have no shortage, and population is peaking. It could peak even sooner if all the children in poor countries are in school; then fertility will fall a lot faster. Population will stabilize at perhaps 9 billion, or 9.2 or 9.3 billion, and will start turning down a lot faster. Even that issue was our great challenge: we went from 1 billion people in 1820 to 8 billion now. That is a lot for societies to absorb. It requires a huge increase in the capital stock, what we call capital widening, just to ensure the basics for a growing population. We no longer have that problem. We can now do capital deepening in a serious way: more technology, more assets, more knowledge, more social capital, more human capital and more natural capital per person, because we are not chasing a rapidly rising population.
So in my view there are no fundamental obstacles other than the political-economy and geopolitical ones. It is mainly our mindset, and mainly political systems geared toward very narrow interests, and in the US case very corrupted interests, mainly the president's family and those who pay his campaign bills. That defines most of American politics right now, maybe until next Tuesday. If we can get past that, we can do wonders.
If you are an economics or politics student, don't just study the trends; think about design, about how to make the world better. That is the most important point. I have two, or rather three, guiding gurus in economics: Adam Smith, John Maynard Keynes and Jan Tinbergen. Jan Tinbergen received the first Nobel Prize in economics. His basic idea was that you have targets and you have instruments, and you set your instruments to achieve your targets. What a beautiful idea. So if you are in politics, political economy or economics, don't just study phenomena and don't just look at predictions; think about design. How could we reach what we want to reach? Then look at the tools we have. They are better than ever, and Professor Layard and Professor Besley are master practitioners of that, so you have gifted teachers for it. Thank you very much.
[Applause]
TIM BESLEY: It just remains for me to thank Jeff for his very, very engaging lecture this evening.