If brain-emulation-based robots, built via an computational reproduction of human brain connections, come to dominate the world economy, that economy will grow far faster than today. Driven by abundance of labour resulting in higher returns to capital and lower commuting costs, most of this activity will be concentrated in a few dense cities.

We live in the age of industry. Our age followed the age of farming, which followed the age of foraging. Each age had its own distinct way of life. During each age the world economy grew at a steady pace, until suddenly, in less than a previous doubling time, it changed radically, and grew over one hundred times faster.

If another age follows ours by the same pattern, then sometime in the next century we’ll see a sudden transition. In less than a decade the world economy would will start doubling every month or faster, and ways of life will change dramatically1 .

There’s a decent chance that such a new era will result from the arrival of robots as smart as humans. In particular, such robots might be created as “brain emulations,” i.e., from taking a particular human brain, scanning it to record its particular cell features and connections, and then building a computer model that processes signals according to those same features and connections.

A good enough emulation, or “em” as I call it, has close to the same overall input-output signal behavior as its original human. An em thinks and feels like a human. One might talk with it, and convince it to do useful jobs. It can be happy or sad, eager or tired, fearful or hopeful, proud or shamed, creative or derivative, compassionate or cold. An em can learn, and have friends, lovers, bosses, and colleagues.

For several years now, I have opportunistically applied standard theories from economics, physics, computer engineering, and many other fields to study the new ways of life that would appear in an em era. I have found, for example, that once the cost to rent an em is substantially less than human subsistence wages, ems quickly dominate the economy. Humans are mostly forced to retire, but live comfortably off of em-economy investments.

From the farmer to the forager to the industrial era, we have consistently seen more and faster growth, larger organizations, more specialization and tool use, more artificial environments, more effective propaganda and drugs, more population density and inequality, and more alienation from work habits that feel natural to foragers. I find that these trends continue in em era.

In this short paper, I focus on two key results related to economies of scale. Economic cost and value vary with many parameters, and one key parameter is scale. That is, cost and value often vary with the total size of a product, plant, firm, city, market, industry, or world. Such economies of scale are important determinants for many kinds of behavior, and this remains true in an em economy.

My two main results are the following. First, an em economy grows faster that ours by avoiding the diminishing returns to capital that we suffer because we can’t grow labour fast enough. Second, an economy has larger cities because it avoids the commuting congestion costs that limit our city sizes.

On Growth

Many em era changes are driven by the fact that ems can be easily copied. Since an em mind can be stored as a digital computer file, it can be copied as easily as such a file. As a result, the size of the em population can grow as fast as factories can make computer hardware to run brain emulation models. This not only causes wages to quickly fall to em subsistence levels, it also allows the em economy to grow much faster, via eliminating a key type of diminishing returns. Let me explain.

The productive capacity of an economy comes from its capacity of inputs, such as land (i.e., raw materials), labor, and capital of various sorts, and also from its level of “technology,” i.e., the ways it has to convert inputs into outputs. While there have been times and places where growth has been driven mainly by increases in inputs, over the long run most growth has come from better technology.

So far, the diffusion of innovation has always been key. Societies have grown via their fastest available way to diffuse innovation, with each new faster diffusion method not feasible until the previous society had reached some minimum economic scale.

For example, foragers doubled roughly every quarter million years. They grew slowly by accumulating more ways to gain from plants and animals, in more kinds of environments. While it was easy to make more foragers, population hit diminishing returns, because it was harder to find new sources of food. Once foragers accumulated a sufficient density and reliability of food sources, they could stop wandering and stay in one place, allowing more physical capital and related innovations, and longer distance trade networks. This allowed farmers to grow in numbers more quickly faster.

During the farming era, when the economy doubled roughly every thousand years, it was easy to increase the population size, and most forms of capital, but growth remained limited because good land was limited. Given limited land there were diminishing returns to labor and capital. Growth mostly had to wait for innovations that made it feasible to take more advantage of available land.

Once farmers had a fine enough division of labor, innovations could diffuse faster, such as via networks of topic specialists. In the industrial economy, we have plenty of land, relative to our needs, and are able to rapidly increase our capital, such as buildings and machines. However, our growth of inputs is still limited by the limited rate at which we can increase the number of skilled laborers. Given limited labor, we suffer diminishing returns to capital. Growth has mostly had to wait for innovations, mostly in better ways to make and use machines. The world economy has lately been doubling roughly every fifteen years.

In an em economy, however, labour can grow as fast as capital. Factories can make more ems to run machines as fast as they can make more machines to be run. While raw materials and real estate on Earth will eventually run out, ems have enormous room to grow before such limits matter much. And while humans must fear ecological collapse leading to economic collapse, ems need not depend on biological resources.

Thus there can be an important early em era where most economic growth comes from simple growth of inputs, i.e., from making more labour and capital as fast as factories can crank them out, in a background of plentiful natural resources. Since an em economy no longer suffers diminishing returns in growing labour and capital together, basic economic theories suggest that an em economy might double in a month, week, or even faster.

On Cities

The sizes of social groups sizes have steadily increased throughout over history. While most mammals live in groups of size two to fifteen2, most human foragers lived in bands of size roughly twenty to fifty. Most farmers lived in village-based communities of size roughly five hundred to two thousand people3 ; while larger empires often existed, they made little difference to most people’s lives. Today most of us live in metropolitan regions of size roughly one hundred thousand to ten million people4.

The size of each era’s communities have been roughly the square of those in the previous era: a band is a group of groups, a village is a band of bands, and a city is a village of villages. If this trend continues, ems would live in mega-communities containing roughly a trillion.

During the industrial era, organizations increased greatly in size and intensity. Cities moved from holding a few percent of the population to holding the majority. Firms moved from employing handfuls to hundreds of thousands. Empires that rarely mattered much to ordinary farmers were replaced by nations, with which individuals identified more strongly and which they saw as more influential over their lives.

Today, doubling a city’s population tends to increase economic productivity by 10% per person. Compared to any given sized city, double-sized cities have 21% more patents, and have 11% shorter roads and 9% shorter electrical cables per person compared with urban centres half the size. But these cities also suffer 12% more crime, 17% more AIDS cases, and 34% more traffic congestion costs per person567.

Optimal city size is in general a tradeoff between these gains and losses. During the farming era most people lived in small communities with populations of roughly near one thousand. There were 25% fewer people living in towns twice as large as any given settlement size. Compared to any given sized town, only about 75% as many people lived in double-sized towns8. Thus most farmers lived in the smallest towns, because during the farmer era larger towns suffered higher costs of crime, disease, and transport.

Within rich nations today, in contrast, people are spread roughly equally across all the different feasible city sizes, between a minimum viable modern town of a few thousand and a maximum city size set by a nation’s population. Compared to any given size city, about the same total number of people live in cities twice as big, and in cities half as big. This change to larger cities from the farming era is possible because industrial society has greatly lowered the costs of crime, disease, and transport, and increased our abilities to gain from specialization and innovation.

An em economy might further reduce the costs of crime and disease, and increase the gains from innovation. After all, well-designed computers can be very secure from theft, assault, and disease. More importantly, traffic congestion costs could be much lower in an em city because most transport of ems could be done via communication lines, and most virtual meetings within a city would not require the movement of em minds at all. Since congestion costs now limit city sizes, this increase in virtual meetings could plausibly tip the balance toward much larger em cities.

Thus instead of today’s equal distribution of people across all feasible city sizes, most ems might instead be found in a few very large cities. Most ems might live in a handful of huge dense cities, or perhaps even just one gigantic city. If this happened, nations and cities would merge; there would be only a few huge nations that mattered. This would represent a massive increase in the economies of scale and scope for cities.