1. In the discussions after the GSS workshop on territorial and functional patterns, Jose Lobo highlighted the 2011 paper on “Cities, Productivity, and Quality of Life” by Glaeser. A key point in the paper is the fact that high-density cities based on high-rise buildings – like the ones China is developing – are more energy efficient than the low-density cities induced by height controls like the ones enacted in India. This is but one example of the choices about urban form that matter for sustainability.

    You envisage a global urban system as a network with nodes called Phoenix, Amsterdam, Kabul, Lagos and so on. Through these nodes flow energy, matter, and information, and presently they flow in ways that are not sustainable. That is a judgement most people with a minimum of background knowledge will share.

    The idea of energy flows seems relatively clear: we can distinguish commercial energy flows like the gas burned in cars from non-commercial ones like the sunshine falling on the just and the unjust alike. Energy flows can be described with physical units for power like Watt, energy itself with units like kilowatthours. That urban studies are intimately connected with energy issues is quite clear, as is the fact that at given levels of income energy use per capita can be reduced by increasing population density.

    Matter is a bit more tricky, as it comes in so many kinds. Take water, clearly an important substance flowing through the global urban system. It can be salt water and fresh water, drinking water or contaminated – and pollution comes in more than fifty shades. Still, we can investigate flows of matter and at least come up with rough estimates, like the amount of water needed to produce a pound of New York steak (at least 2500 gallons or 10 cubic meters).

    Information is hard. In physics, the gasoline in the gas tank of a car has lower entropy than the CO2 and water leaving its exhaust pipe, which means that the expected value of the information conveyed by the precise micro-state of the gasoline is lower than the expected value of the information conveyed by the micro-state of the exhaust gases. This is not the kind of information we are interested in here. In computing, the information content of an arbitrary string of zeroes and ones is often identified with the length of the string. If we code yesterday’s sunset as 1 and all other things we may be interested in as any other string of zeroes and ones, then the information content of yesterdays sunset is one bit. There are several other more or less clear notions of information around, but none fits the bill of urban studies in general. For the moment, the best we can do is to trust our common sense as ICT users and speak of information flows in ambiguous ways that sometimes can be pinned down as something measurable, and sometimes not.

    Prices, e.g., convey some kind of information, and clearly they matter a lot for urban dynamics. But what kind of information do they convey? Adam Smith and the other classical economists thought that somehow they told how much labor was needed to produce something. This is not as weird as it may seem to us today, as it certainly takes more labor to produce a Rolls-Royce than a Fiat 500. Still there are problems with that view, one of which is the fact that prices of land cannot really be understood as reflecting the amount of labor needed to produce land.

    So economists developed the view that prices reflect the marginal utility to be gained from an additional unit of different goods (which is what is called scarcity in economics). The price of a square meter of ground in the Netherlands corresponds to the additional utility to be gained if the Dutch snap another square meter from the sea. There are serious problems with that view, too, however. First and foremost: whose utility? One might think some sort of aggregate Dutchman formed by weighting the wishes and needs of dutch people with their wealth. But even this would not do, because different prices for land can change these weigths so as to lead to different equilibria. The truth is that as a society relying very much on price signals, we do not know what information they convey.

    Given the role of house prices in triggering the first global economic crisis since nearly a century, it is quite interesting that we do not know what is the information conveyed by prices. Looks like a nice puzzle for global systems science, especially when looking at urban systems.

    And perhaps we will manage to solve that puzzle, too, if we address the research questions you outline in your post.

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