Archive for the ‘Population’ Category

Log cabin

In my mind, my hometown will always be a city of 24,000 people. It’ll also be supported by three major manufacturing companies. And it’ll always have a certain, intangible something. Of course, today West Bend has 5,000 more residents despite the demise of all three manufacturers. And every time I return, that certain something isn’t quite the same either. It’s like waking from a dream I can’t entirely reconstruct.

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Gold L.A.

The U.S. Census released a report on urban population on Monday, and in it was a perhaps-unexpected fact: Of the ten most densely populated cities, seven of them are in California. Indeed, California’s showing was so strong that the great bastion of urbanism in the United States — the New York-Newark metro area — just barely made the top five.

John King, the San Francisco Chronicle’s urban design critic, interviewed a number of experts about California’s unique status. Among them was Jon Christensen, executive director of the Bill Lane Center for the American West at Stanford University. One of Christensen’s quotes caught my attention, so I followed up with him via email to explore why California is such a hotbed of urbanism. Our correspondence follows:

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Map of photos taken in Minneapolis and St. Paul, Minnesota

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Cities were, for thousands of years, distinct and easily identifiable entities. You were either in the city or in the country. Medieval cities took this to the extreme, building walls to make explicit the distinction. Johann Heinrich von Thünen systematized the idea in 1826 when he sketched a hypothetical map that, when simplified, looked like a bow-and-arrow target. The city sat in the center and was surrounded by rings of successively less valuable farmland. It was all very orderly and very German. And for a while it did a good job describing the relationship between the city and the hinterland.

Then came the railroads and automobiles that shot holes through von Thünen’s well-organized bullseye. And in places where two cities were less than a few dozen miles apart, even the boundary between the two became blurred. Today, it’s not uncommon to find metropolitan areas with two, three, even four major cities anchoring them.

Von Thunen's model of land use

Multi-city metros would seem to be a many-headed monster, riddled with contrary opinions and paralyzed by indecision. But that doesn’t alway seem to be the case. As far as labor productivity is concerned, multi-city metros—or polycentric metros, as the literature calls them—may have a distinct advantage. A study of all metropolitan areas in the United States with populations above 250,000 by Evert Meijers and Martijn Burger shows that productivity is higher in metros with more than one city. The effect is especially pronounced among smaller metro areas.

Meijers and Burger speculate that’s because smaller cities tend to have smaller problems—less traffic, lower crime rates, and so on. By splitting the problems up among a few cities, polycentric metros can host a large population without experiencing the problems of a similarly sized, monocentric metro.

But the advantages of multi-city metros diminish as the entire area’s population grows. It’s as though the larger entity needs one place to focus its efforts. So a metro area with two cities, each one-half the size of London, wouldn’t necessarily be more productive than London itself.

Multi-city metros also fall short on other critical parts of city life—cultural and leisure opportunities. Cultural outposts like opera houses and art museums benefit greatly from larger populations, which typically contain more benefactors, both wealthy and otherwise. The same goes for sports teams. Every city would like one for themselves. Say Ft. Worth wants to build an art museum. It’s probably not going to attract some donors from Dallas, who would rather see one built in their city. Chicago doesn’t have such a problem. Monocentric metros don’t have to worry about sharing.

As cities’ borders swell, multi-city urban agglomerations are probably going to be more and more common. Even within existing metropolitan areas, smaller cities could rise to prominence. Minneapolis and St. Paul, for example, have had to contend with the rise of Bloomington. The key will be for leaders to learn to work together, coordinating efforts rather than stepping on each other’s toes.


Meijers, E. (2008). Summing Small Cities Does Not Make a Large City: Polycentric Urban Regions and the Provision of Cultural, Leisure and Sports Amenities Urban Studies, 45 (11), 2323-2342 DOI: 10.1177/0042098008095870

Meijers, E., & Burger, M. (2010). Spatial structure and productivity in US metropolitan areas Environment and Planning A, 42 (6), 1383-1402 DOI: 10.1068/a42151

Map of the Twin Cities by the inimitable Eric Fischer.

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New York City skyline

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Q: Why is New York City the most populous city in the United States?

A. Because it was America’s most populous city in 1900.

Q. Why was New York City America’s most populous city in 1900?

A. Because it was America’s most populous city in 1800.

History seems to be protecting New York City’s status as the most populous city in the United States. Indeed, Paul Krugman has suggested that accidents of history gave New York City a leg up on others, and that once favored it grew into the metropolis we know today. But New York is not alone. Since 1840, the densest American cities have not only grown substantially, they also represent a larger share of the American population. The same can be said of other world cities, too. They are like snowballs—they’re big and they keep on getting bigger.

But how big cities gained the upper hand is not necessarily an accident, as Krugman’s use of the word might suggest. What has helped them grow so large is actually a specific set of geographic characteristics—location near an ocean or river (or better, both), mild climate, and ready access to natural resources. City founders may not have been working off a checklist, but they knew where to site their settlements to make the most of their surroundings.

It’s no surprise that prosperous cities are often located near large bodies of water. Water is the cheapest way to move goods, and was even more so before the Industrial Revolution. Access to navigable water meant food and raw materials could be easily brought to market and goods manufactured in the city could be cheaply exported. Water facilitated the movement of ideas, too. Both New York City and San Francisco, for example, benefitted from their status as major gateways for immigration. Immigrants were not merely a source of labor—they brought with them a diversity of ideas. Eventually, the importance of water subsided as railroads and interstate highways were built. Yet cities that were founded on coastlines or rivers continued to dominate.

Their size was the secret to their success. One of Krugman’s important early contributions was a model that showed how an already large city could grow to dominate the region. His theory was really nothing new—Johann Heinrich von Thünen described nearly the same thing in 1826—but Krugman translated the concept into today’s mathematical vernacular. Other researchers quickly picked up the thread and dug out real-world evidence of the snowball effect, including one study that looked at population growth in nearly 800 American counties between 1840–1990. It found that not only did the biggest cities grow during that time, they grew at a faster rate than other cities. New York grew more than the rest because it was bigger than the rest.

Today, New York’s fate doesn’t depend on the ocean or the river, but it does owe its status to their confluence. Its geographic past continues to steer its future. I’m tempted to haul out a favorite phrase of mine—ghosts of geography—but these cities aren’t really ghosts. They’re are very much alive. Oceans and rivers may not be as relevant to today’s world cities as they once were, but without them, many cities wouldn’t be as successful. From that perspective, it seems less likely that the founders of New York, London, and Tokyo stumbled on a happy accident and more likely that they had a keen understanding of geography.


Ayuda, M., Collantes, F., & Pinilla, V. (2009). From locational fundamentals to increasing returns: the spatial concentration of population in Spain, 1787–2000 Journal of Geographical Systems, 12 (1), 25-50 DOI: 10.1007/s10109-009-0092-x

Beeson, P. (2001). Population growth in U.S. counties, 1840–1990 Regional Science and Urban Economics, 31 (6), 669-699 DOI: 10.1016/S0166-0462(01)00065-5

Gibson, Campbell. 1998. Population of the 100 largest cities and other urban places in the United States: 1790 to 1990. U.S. Bureau of the Census, Population Division Working Paper No. 27.

Krugman, P. (1991). Increasing Returns and Economic Geography Journal of Political Economy, 99 (3) DOI: 10.1086/261763

Photo by Greg Knapp.

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:amborghini Aventador in traffic

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Yours. Mine. Even a two year-old can understand the basics of ownership. Those two words are also freighted with meaning, implying volumes about resources, control, privilege, and social standing. But what they don’t say is why it is we care so much about who owns what.

There are a number of possible reasons for why we value our possessions and covet those of others. True to form, I found one paper that suggests that population density may be responsible for the evolution of ownership. It’s a game theoretic study by Japanese behavioral scientist Shiro Horiuchi in which he uses an established mathematical model—the Hawk-Dove-Bourgeois game—to sift through the possible origins of possession in both animals and humans.

The Hawk-Dove-Bourgeois game (HDB) is a modification of the classic Hawk-Dove game. In addition to the two existing player types—hawks, who fight to acquire resources or territory and viciously defend what’s theirs, and doves, who avoid conflict at all costs—HDB adds a third strategy, called bourgeois. Bourgeois are a bit of a hybrid of the two existing approaches. A bourgeois player, when challenged for ownership, will fight furiously to keep it. But unlike hawks, they won’t attack other players to acquire resources.

Horiuchi took this game and threw out the standard dove and bourgeois strategies, replacing them instead with strong and weak bourgeois. Weak bourgeois are more similar to doves, which means they are less likely to engage in conflicts. Strong bourgeois can adopt a hawk- or dove-like stance depending on their territorial boundaries: If the contested area is within their boundaries, they’ll fight like hawks. If not, they’ll sit out like doves. Players can change strategies depending on how well they are doing relative to their neighbors. The goal is to control 10 units of territory.

In layman’s terms, the strong bourgeois strategy is a proxy for ownership in its purest sense—strong bourgeois players only fight to retain what’s theirs; anything else and they abstain from conflict. And what emerged from the games was a clear picture of strong bourgeois dominance at higher population densities. That doesn’t mean strong bourgeois players controlled more territory—remember, they were limited to a maximum of 10 units. Rather it means that more players adopted that strategy, judging that it was the best way to obtain and hold the maximum territory, especially as the playing field became more crowded.

Previous studies that used the unmodified HDB game didn’t come to the same conclusion, arguing that the bourgeois strategy—ownership, in other words—isn’t advantageous when resources are high. But those findings are refuted by real world studies of primates that show groups are willing to defend resource-rich home ranges, Horiuchi points out. His modifications and results more closely match the empirical data and suggest that ownership not only arises as population densities increase, but that it’s the best way to succeed.

As an ecologist, this result did not surprise me. In ecology, resources are everything. Even organisms as sedate as plants compete ferociously for resources, employing competitive tactics that range from rapid growth to chemical warfare. But in modern, developed societies where the bare necessities are frequently met, I wondered how these findings might apply. I ran Horiuchi’s result past a friend of mine who is a social psychologist, and he indicated that ownership today is not merely about resources, but status. Controlling more territory—or even just expressing one’s wealth in ever more ostentatious ways through possessions—is just another way in which the strong bourgeois strategy could continue to exert its influence, even though we’re not struggling to survive.

Frankly, I’m not surprised. Based on anecdotal observations of the various places I’ve lived, possessions appear to play a larger role in people’s lives the denser and more populous a city becomes. In large cities, people who earn double their peers seem more inclined to flaunt that wealth compared with the same individuals in smaller towns. The social psychological explanation makes sense in this case. It’s harder to stand out in denser, more populous places, which may lead to more conspicuous consumption.


Horiuchi, S. (2007). High population density promotes the evolution of ownership Ecological Research, 23 (3), 551-556 DOI: 10.1007/s11284-007-0408-6

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Agrippina the Younger

Over the last 30 years, wealth in the United States has been steadily concentrating in the upper economic echelons. Whereas the top 1 percent used to control a little over 30 percent of the wealth, they now control 40 percent. It’s a trend that was for decades brushed under the rug but is now on the tops of minds and at the tips of tongues.

Since too much inequality can foment revolt and instability, the CIA regularly updates statistics on income distribution for countries around the world, including the U.S. Between 1997 and 2007, inequality in the U.S. grew by almost 10 percent, making it more unequal than Russia, infamous for its powerful oligarchs. The U.S. is not faring well historically, either. Even the Roman Empire, a society built on conquest and slave labor, had a more equitable income distribution.

To determine the size of the Roman economy and the distribution of income, historians Walter Schiedel and Steven Friesen pored over papyri ledgers, previous scholarly estimates, imperial edicts, and Biblical passages. Their target was the state of the economy when the empire was at its population zenith, around 150 C.E. Schiedel and Friesen estimate that the top 1 percent of Roman society controlled 16 percent of the wealth, less than half of what America’s top 1 percent control.

To arrive at that number, they broke down Roman society into its established and implicit classes. Deriving income for the majority of plebeians required estimating the amount of wheat they might have consumed. From there, they could backtrack to daily wages based on wheat costs (most plebs did not have much, if any, discretionary income). Next they estimated the incomes of the “respectable” and “middling” sectors by multiplying the wages of the bottom class by a coefficient derived from a review of the literature. The few “respectable” and “middling” Romans enjoyed comfortable, but not lavish, lifestyles.

Above the plebs were perched the elite Roman orders. These well-defined classes played important roles in politics and commerce. The ruling patricians sat at the top, though their numbers were likely too few to consider. Below them were the senators. Their numbers are well known—there were 600 in 150 C.E.—but estimating their wealth was difficult. Like most politicians today, they were wealthy—to become a senator, a man had to be worth at least 1 million sesterces (a Roman coin, abbreviated HS). In reality, most possessed even greater fortunes. Schiedel and Friesen estimate the average senator was worth over HS5 million and drew annual incomes of more than HS300,000.

After the senators came the equestrians. Originally the Roman army’s cavalry, they evolved into a commercial class after senators were banned from business deals in 218 B.C. An equestrian’s holdings were worth on average about HS600,000, and he earned an average of HS40,000 per year. The decuriones, or city councilmen, occupied the step below the equestrians. They earning about HS9,000 per year and held assets of around HS150,000. Other miscellaneous wealthy people drew incomes and held fortunes of about the same amount as the decuriones.

In total, Schiedel and Friesen figure the elite orders and other wealthy made up about 1.5 percent of the 70 million inhabitants the empire claimed at its peak. Together, they controlled around 20 percent of the wealth.

These numbers paint a picture of two Romes, one of respectable, if not fabulous, wealth and the other of meager wages, enough to survive day-to-day but not enough to prosper. The wealthy were also largely concentrated in the cities. It’s not unlike the U.S. today. Indeed, based on a widely used measure of income inequality, the Gini coefficient, imperial Rome was slightly more equal than the U.S.

The CIA, World Bank, and other institutions track the Gini coefficients of modern nations. It’s a unitless number, which can make it somewhat tricky to understand. I find visualizing it helps. Take a look at the following graph.

Gini coefficient of inequality

To calculate the Gini coefficient, you divide the orange area (A) by the sum of the orange and blue areas (A + B). The more unequal the income distribution, the larger the orange area. The Gini coefficient scales from 0 to 1, where 0 means each portion of the population gathers an equal amount of income and 1 means a single person collects everything. Schiedel and Friesen calculated a Gini coefficient of 0.42–0.44 for Rome. By comparison, the Gini coefficient in the U.S. in 2007 was 0.45.

Schiedel and Friesen aren’t passing judgement on the ancient Romans, nor are they on modern day Americans. Theirs is an academic study, one used to further scholarship on one of the great ancient civilizations. But buried at the end, they make a point that’s difficult to parse, yet provocative. They point out that the majority of extant Roman ruins resulted from the economic activities of the top 10 percent. “Yet the disproportionate visibility of this ‘fortunate decile’ must not let us forget the vast but—to us—inconspicuous majority that failed even to begin to share in the moderate amount of economic growth associated with large-scale formation in the ancient Mediterranean and its hinterlands.”

In other words, what we see as the glory of Rome is really just the rubble of the rich, built on the backs of poor farmers and laborers, traces of whom have all but vanished. It’s as though Rome’s 99 percent never existed. Which makes me wonder, what will future civilizations think of us?


Scheidel, W., & Friesen, S. (2010). The Size of the Economy and the Distribution of Income in the Roman Empire Journal of Roman Studies, 99 DOI: 10.3815/007543509789745223

Photo by Biker Jun.

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Class portrait, unknown English school (undated)

Without the Industrial Revolution, there would be no modern agriculture, no modern medicine, no climate change, no population boom. A rapid-fire series of inventions reshaped one economy after another, eventually affecting the lives of every person on the planet. But exactly how it all began is still the subject of intense debate among scholars. Three economists, Raouf Boucekkine, Dominique Peeters, and David de la Croix, think population density had something to do with it.

Their argument is relatively simple: The Industrial Revolution was fostered by a surge in literacy rates. Improvements in reading and writing were nurtured by the spread of schools. And the founding of schools was aided by rising population density.

Unlike violent revolutions where monarchs lost their heads, the Industrial Revolution had no specific powder-keg. Though if you had to trace it to one event, James Hargreaves’ invention of the spinning jenny would be as good as any. Hargreaves, a weaver from Lancashire, England, devised a machine that allowed spinners to produce more and better yarn. Spinners loathed the contraption, fearing that they would be replaced by machines. But the cat was out of the bag, and subsequent inventions like the steam engine and better blast furnaces used in iron production would only hasten the pace of change.

This wave of ideas that drove the Industrial Revolution didn’t fall out of the ether. Literacy in England had been steadily rising since the 16th century when between the 1720s and 1740s, it skyrocketed. In just two decades, literacy rose from 58 percent to 70 percent among men and from 26 percent to 32 percent among women. The three economists combed through historical documents searching for an explanation and discovered a startling rise in school establishments starting in 1700 and extending through 1740. In just 40 years, 988 schools were founded in Britain, nearly as many as had been established in previous centuries.

School establishments in Great Britain before 1860

The reason behind the remarkable flurry of school establishments, the economists suspected, was a rise in population density in Great Britain. To test this theory, they developed a mathematical model that simulated how demographic, technological, and productivity changes influenced school establishments. The model’s most significant variable was population density, which the authors’ claim can explain at least one-third of the rise in literacy between 1530 and 1850. No other variable came close to explaining as much.

Logistically, it makes sense. Aside from cost, one of the big hurdles preventing children from attending school was proximity. The authors’ recount statistics and anecdotes from the report of the Schools Inquiry Commission of 1868, which said boys would travel up to an hour or more each way to get to school. One 11 year old girl walked ten miles a day for her schooling.

Many people knew of the value of an education even in those days, but there were obvious limits to how far a person could travel to obtain one. Yet as population density on the island rose, headmasters could confidently establish more schools, knowing they could attract enough students to fill their classrooms. What those students learned not only prepared them for a rapidly changing economy, it also cultivated a society which valued knowledge and ideas. That did more than just help spark the Industrial Revolution—it gave Great Britain a decades-long head start.


Boucekkine, R., Croix, D., & Peeters, D. (2007). Early Literacy Achievements, Population Density, and the Transition to Modern Growth Journal of the European Economic Association, 5 (1), 183-226 DOI: 10.1162/JEEA.2007.5.1.183

Stephens, W. (1990). Literacy in England, Scotland, and Wales, 1500-1900 History of Education Quarterly, 30 (4) DOI: 10.2307/368946

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Photo scanned by pellethepoet.

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