Interaction Maximization and the Observed Distribution of Urban Populations:
An agent-based model of humanity’s metric condition

André Ourednik, Pierre Dessemontet @ EPFL ENAC Chôros

Presented at the 15th European Colloquium on Theoretical and Quantitative Geography (ectqg'07) , 7-11 september in Montreux, Switzerland.

Published in the Colloquium Proceedings, ISBN: 978-2-940368-05-1.


The very existence of urban formations on all inhabited continents and throughout the history of mankind since the 3rd millennium B.C. leads to suppose a tendency of some structured societies to maximize interaction by minimizing physical distance. Were this tendency unconstrained, it should eventually lead to the concentration of all of the society’s population into one single point: a situation only partially realized by the distribution of urban populations at the global scale. Models of constraints preventing its realization have thus to be proposed. We have set up one such model, using agent based simulation of food production and accessibility, in order to account for the structural constraints particular to the physical space. The simulations have notably shown that, while necessarily emerging from a society investing agricultural surplus into the upholding of specialists, an upper limit to city-growth is imposed by the phenomena of spatial friction.

Model explanation

> > > Slide presentation (pdf.), with detailed model explanation.

Choose the interactive model version

v2 - growth, death and concentration

In this extended version, new cities can emerge, and disappear in any place on the map. A logistic function is used to determine growback based on the number and disatance of urban specialists.

v1 - Simple concentration

In this simple version, cities only grow and decline in 100 predefined locations.


The applets (Created with NetLogo3.1.4) require Java 1.4.1 or higher to run. It will not run on Windows 95 or Mac OS 8 or 9. Mac users must have OS X 10.2.6 or higher and use a browser that supports Java 1.4 applets (Safari works, IE does not). On other operating systems, you may obtain the latest Java plugin from Sun's Java site.

Accelerated Simulation Example: "Parasitic Cities"

An accelerated simulation of the 2nd version, with extreme settings: maximum growback, maximum reach, no urban spetialist effect. Think of Ancient Rome...


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André Ourednik, Pierre Dessemontet

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