Energized Crowding Turns Cities into Social Reactors

What is is about cities that makes them exciting and dynamic? Things are happening in cities and people are attracted to them. As Jane Jacobs said, “Cities have the capability of providing something for everybody, only because, and only when, they are created by everybody.” Some cities never sleep. Cities are the setting for activities that just aren't found in smaller settlements. The more people in a city, the more activity and the more excitement. This is not just a feature of contemporary cities:  ancient cities like Teotihuacan were also bustling, dynamic, and attractive places. Architectural historian Spiro Kostof coined the term "energized crowding" to describe this aspect of urban life and society.

Energized crowding doesn't just describe the condition of life in cities - it describes the basic social forces that lead cities to grow and to transform life and society. This is the basis of the work on settlement scaling by the Social Reactors Project: me and Jose Lobo at Arizona State University, Scott Ortman at the University of Colorado, and Luis Bettencourt at the Santa Fe Institute. Check out our website. In our model, the process of energized crowding turns cities into social reactors.

As the number of people in a settlement increases, the number of potential social interactions grows at an exponential rate (see graph). As settlements grow larger, the effects of social interaction are amplified. These include positive, negative, and neutral effects. Let's start with the negative side of things. As we as individuals have to deal with more and more people, we get overloaded. Too many people, too much going on. This is called scalar stress. Some of the effects are highly negative--more people means more crime, more poverty, more social alienation. But scalar stress is offset by one of the big "nuetral" effects of growing settlement: the formation of neighborhoods. As cities grow, people adjust their activities so that they can live life on a smaller scale--the neighborhood. As I have said many times in this blog, neighborhoods are one of the very few universals of the urban experience. Here are a few posts on this (out of many.....):

• How do neighborhoods form?
• Why do all cities have neighborhoods?
• Archaeology and pink flamingos in Chicago neighborhoods

 But there are also positive effects of energized crowding. Urban economists and economic geographers have known for a long time that when businesses and industries concentrate themselves in cities, it leads to economies of scale and thus major gains in productivity. These effects are called agglomeration effects, as in this diagram:

But it turns out that the positive effects of concentration and energized crowding are not limited to the modern industrial economy. In fact, they occur in cities before the industrial revolution, whether medieval European cities, or cities in the Roman or Inka empires. This fact alone shows that these effects are not due to factories, wage labor, advanced transportation, or other attributes of modern economies. In fact, these effects arise primarily out of the very act of social interaction within the built environment.

This realization was a real breakthrough in our understanding of the nature of city size and its role in generating the social and economic properties of cities. The key paper is Bettencourt (2013). Luis derives a quantitative model that predicts characteristics of cities based on their sizes, within a given region or urban system. The beauty of the model is that its conditions are general enough to fit cities before the modern era. In fact they also should work for non-urban settlements in agricultural village societies (and they do!).

Below is my diagram of energized crowding (from Smith 2017). When population grows, leading to higher densities, energized crowding increases. This can happen from regional population growth, or it can arise from the process of people moving into cities. The three results shown here are the negative, neutral, and positive outcomes of energized crowding.

In the time since Luis's 2013 article, our group has been scouring archaeology and history for cases where we can try out the model. Scott Ortman initiated this work with his studies of the settlement in the prehispanic Basin of Mexico. We've published a number of studies, and a bunch more are in the pipeline. Scott has even found the same scaling effects in village societies. The data requirements are heavy (a sample of 30 or more settlements from a given region and time period, with population estimates and other quantitative data to scale against population). If you think you know of any such cases, please let me know!

We have found the same quantitative relationships in modern and ancient settlement systems. This suggests that the same or very similar fundamental social processes operate when humans come together in settlements, whether today or two thousand years ago. Energized crowding--which is at a much higher level in larger settlements--has measurable effects on the density of settlement, and on the levels of economic and social outputs. In this figure, Graph A shows economic output measures for the modern U.S. economy, while Graph B shows wealth output for the ancient Inka economy. Quantitatively these two graphs are nearly identical. Both exhibit "superlinear scaling," with beta coefficients of 1.13.

So, how far can we push these relationships? Are they universal? Well, not quite. Hunter-gatherer campsites show very different patterns from the agricultural societies we have studied so far. This is something we are working on now. But for most systems we have examined, we find similar patterns, and when we apply Luis's model, we conclude that energized crowding turns settlements into social reactors.

For some other posts on the scaling work, see:

•  Cities as social reactors.
• Settlement scaling and social science theory

See our project website for more information.


Bettencourt, Luís M. A.  2013    The Origins of Scaling in Cities. Science 340: 1438-1441.

Cesaretti, Rudolf, Luís M. A. Bettencourt, Jose Lobo, Scott Ortman, and Michael E. Smith 2016    Population-Area Relationship in Medieval European Cities. PLOS-One: 11:(10) e162678.  .

Ortman, Scott G., Andrew H.F. Cabaniss, Jennie O. Sturm, and Luís M. A. Bettencourt
2014    The Pre-History of Urban Scaling. PLOS-one 9 (2): e87902.

2015    Settlement Scaling and Increasing Returns in an Ancient Society. Science Advances 1 (1): e1400066.

Ortman, Scott G. and Grant D. Coffey  2015    Universal Scaling: Evidence from Village-Level Societies. SFI Working Paper, vol. 15-10-044. Santa Fe Institute, Santa Fe. 

Ortman, Scott G., Kaitlyn E. Davis, José Lobo, Michael E. Smith, Luis M.A. Bettencourt, and Aaron Trumbo  2016    Settlement Scaling and Economic Change in the Central Andes. Journal of Archaeological Science 73: 94-106.  .

Smith, Michael E.  2017    The Generative Role of Settlement Aggregation and Urbanization. In Coming Together: Comparative Approaches to Population Aggregation and Early Urbanization, edited by Attila Gyucha. State University of New York Press, Albany.

Cities as social reactors

Fig 1. Inka storehouses

Some traits of cities seem universal, shared by all cities, large and small, past and present. Neighborhood organization is one of these urban universals, something I have talked about in previous posts (here, and here, for example).  See Smith et al. (2015). Other traits seem more limited to only some kinds of cities, or cities in only a few regions or periods. For example, Inka cities were full of standardized stone storage facilities, built and maintained by the state (Figure 1); such storehouses are rare in other cities. Contemporary cities have organized trash pick-up (whether government or privately run), while past cities lacked this institution. One of my reasons for writing this blog is to explore the nature of these similarities and differences among cities across the span of deep history and around the globe.

A number of lines of research now suggest that that the role of cities as “social reactors” may be another urban universal. This means that the presence of greater numbers of people—in larger settlements—leads to more social interactions, which in turn produces social and economic benefits far beyond what smaller settlements can produce. Cities are places where individuals interact socially in all kinds of ways. As the number of people in a city goes up, the number of potential interactions with other people also rises, but it rises much faster than the number of people. The increase is exponential (Figure 2). These interactions have been called "buzz" (Storper and Venables 2004).

Fig 2. Interactions & pop.

A long line of research in the social sciences focuses on the negative consequences of growing city size. More people means more crowding, and crowding in cities can cause stress, both psychological and social. Larger cities have more crime and more poverty. Social relations may be less personal in larger cities, with neighbors less willing to help one another. One intriguing theory, by archaeologist Roland Fletcher (1995), posits thresholds of population size and density that growing settlements cannot cross unless they develop new means of communication and social integration (Figure 3). Otherwise the stresses of living with too many people make life intolerable and settlements will disintegrate or break down.  When early village dwellers figured out how to communicate information with writing, and how to divide their settlements into increasingly specialized spaces and buildings, they could achieve the transition to the first cities, which had more people and denser populations.

 

Fig. 3. Fletcher's book

Growing city size also has its positive consequences. In early times, the most basic attraction of city life was protection. War and violence have been prominent in all eras of history. Once our ancestors adopted agriculture and settled down, the concept of property was born. Property and riches led to crime and warfare. People quickly figured out that there was strength in numbers. Kings and rulers in past times wanted their subjects to move into town. People were easier to tax and control in cities, and their economic activity created growth and prosperity that benefitted the rulers.

Now let's jump to the present. In contemporary cities, urban growth has what economists call “agglomeration effects” (Figure 4). This means that as firms and factories set up in cities, they attract workers and create greater specialization and increased productivity. These in turn generate growth, attracting even more people to cities and creating more output. The spatial concentration of people and firms in cities leads to economies of scale, which pushes urban productivity even higher. Knowledge and skills can be transferred among people, and from one industry to another, because of their concentration in a city.

 

Figure 4.  Agglomeration effects

This picture of agglomeration economies is a pretty standard view of contemporary cities, as seen by urban economists and economic urban geographers. It is easy to see how cities in this sense can be called “social reactors.” They are places where concentrations of people, firms, and institutions create wealth and growth, built on a foundation of the way the people interact with one another. This is definitely the way cities operate within modern capitalist economies. But what about cities before the modern era, before the birth of capitalism? They didn’t have wage labor; workers did not move among firms and industries as they do today; land markets were rudimentary or non-existent; and economies were far less dynamic than they are today.

Were cities in the past also “social reactors”? My answer to this question a few years ago would have been “no.” It seemed to me (and to many urban scholars) that the generative properties of cities—their capacity to grow quickly and expand economically, their ability to create wealth—arose from the capitalist economy. Ancient cities did not have agglomeration economies, and thus their roles as social reactors must have been far less important than today.

But then I started working on urban scaling with three colleagues. The results have been surprising and illuminating to me, and important for a general understanding of urbanism. I’ve blogged a bit about the scaling work previously (an early post, and later), and I will talk about it more in the future. For now, I will say that this research had convinced me that the concept of social reactors definitely applies to ancient cities, and it even applies to large villages and towns. Something fundamental happens when people live together in settlements, and these fundamental processes become stronger as a settlement gets bigger.

Here is a very brief description of three reasons why I changed my mind on ancient cities and settlements as social reactors.

First, the very regular patterns of how urban traits change with city population, as found for contemporary cities, also apply to past cities. These relationships are analyzed with scaling models, and our research group has found that the scaling patterns of modern cities are also present in cities before the modern era.

 

Fig. 5. Mandan village

Second, these scaling relationships are also found in village settlements among tribal peoples (Figure 5). To me, this is an astounding finding. Generative processes that are thought to be “urban” in nature also affect much smaller settlements in societies that lack cities, kings, laws, and social classes. Wow, this is nothing short of incredible.

Third, the explanation for the above reasons comes from Luis Bettencourt’s (2013) formal model of scaling. Rather than tracing the city dynamics that create scaling to agglomeration economies, this model traces them to face-to-face social interaction within a structured built environment. This means that they should be present in historical cities, in ancient cities, and in non-urban village settlements. And they are!

After a few years of working groups and meetings our project now has a name: “The Social Reactors Project: Human Settlement and Networks in History” and a website. We are physicist Luis Bettencourt, economist Jose Lobo, archaeologist Scott Ortman, and me. Our website has just gone live this week! Check it out for our work and papers, and for the names of postdocs and students who are helping.

The idea that face-to-face social interactions (buzz) are crucial to cities and to urban life is nothing new. Here are three quotes from diverse authors:

“The central theme of this book is that cities magnify humanity’s strengths. Our social species’ greatest talent is the ability to learn from each other, and we learn more deeply and thoroughly when we’re face-to-face.”

--Urban economist Edward Glaeser (2011:250).

“Again and again, we find that one key to creating social capital is to build in redundancy of contact. … Common spaces for commonplace encounters are prerequisites for common conversations and common debate.”

-- Political scientist Robert Putnam and Civic leader Lewis Feldstein (Putnam and Feldstein 2003:291).

“Stable physical settings” promote community. “The neighborhood accommodates and facilitates social interaction.”

--Urban planner Sidney Brower (Brower 2011:19)

I believe this notion was also crucial to past communities, a theme I develop in my new book, At Home with the Aztecs: An Archaeologist Uncovers their Daily Life.

The innovation of our scaling research group is to demonstrate, with solid quantitative data, that these face-to-face interactions were not only present and important in the past, but that they also generated change and output in the past, just as they do today. We have a bunch of papers in production and in press, and some published (see the website). The role of cities as social reactors is not just a contemporary phenomenon, an attribute of capitalist economies. Rather, it is a fundamental attribute of human settlements through deep history and across space.

References

Bettencourt, Luís M. A.

2013  The Origins of Scaling in Cities. Science 340: 1438-1441.

Brower, Sidney N.

2011  Neighbors and Neighborhoods: Elements of Successful Community Design. APA Planners Press, Chicago.

Fletcher, Roland

1995  The Limits of Settlement Growth: A Theoretical Outline. Cambridge University Press, New York.

Glaeser, Edward L.

2011  The Triumph of Cities: How our Greatest Invention Makes us Richer, Smarter, Greener, Healthier, and Happier. Penguin, New York.

Putnam, Robert D. and Lewis M. Feldstein

2003  Better Together: Restoring the American Community. Simon and Schuster, New York.

Smith, Michael E., Ashley Engquist, Cinthia Carvajal, Katrina Johnston, Amanda Young, Monica Algara, Yui Kuznetsov, and Bridgette Gilliland

2015  Neighborhood Formation in Semi-UrbanSettlements. Journal of Urbanism 8(2): 173-198.

Storper, Michael and Anthony J. Venables
2004    Buzz: Face-to-Face Contact and the Urban Economy. Journal of Economic Geography 4 (4): 351-370.