Games - Tragedy of the commons

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	Games - Tragedy of the commons

The tragedy of the commons is a phrase used to refer to a class of phenomena that involve a conflict for resources between individual interests and the common good. The term derives originally from a parable published by William Forster Lloyd who was Drummond Professor at Oxford and a Fellow of the Royal Society, in his 1833 book on population. It was then popularized and extended by Garrett Hardin in his 1968 Science essay "The Tragedy of the Commons". See also the related real-world event of the 'Enclosure of the commons', and its attendant social problems, which may have inspired the content of the parable. The opposite situation to a tragedy of the commons is sometimes referred to as a tragedy of the anticommons.

Introduction

The parable demonstrates how unrestricted access to a resource such as a pasture ultimately dooms the resource because of over-exploitation. This occurs because the benefits of exploitation accrue to individuals, while the costs of exploitation are distributed between all those exploiting the resource.

Like William Lloyd, Hardin was primarily interested in population and especially the problem of human population growth (similarly also to Thomas Malthus). However, he also focused more generally on the use of resources such as the atmosphere and oceans, as well as pointing out the 'negative commons' of pollution.

Similar to the phrase "Survival of the fittest", coined by Herbert Spencer and also widely misinterpreted, the "Tragedy of the commons" is a metaphor chosen for the way it "trips off the tongue", and should not be taken too literally as defining the concept. Hardin himself said that he used the word 'tragedy' in the sense that the philosopher Alfred Whitehead used it: "the remorseless working of things". The phrase is shorthand for a phenomenon, not an accurate description of it. Furthermore, the "tragedy" should not be seen as tragic in the conventional sense, nor must it be taken as condemnation of the processes that are ascribed to it.

The 'Tragedy of the Commons' has particular relevance in explaining behaviour in the fields of evolutionary psychology and sociology. More generally, it can be seen as an example of game theory, with the trading of costs and benefits between "players". Some also see it as an example of emergent behaviour, with the 'tragedy' the outcome of individual interactions in a complex system.

Garrett Hardin's essay

At the beginning of his essay, Hardin draws attention to problems that cannot be solved by technical means (i.e. as opposed to those problems with solutions that require "a change only in the techniques of the natural sciences, demanding little or nothing in the way of change in human values or ideas of morality"). Hardin contends that this class of problems includes those raised by human population growth and the use of the Earth's natural resources.

To make the case for "no technical solutions", Hardin notes the limits placed on the availability of energy (and material resources) on Earth, and also the consequences of these limits for "quality of life". To maximise population, one needs to minimise resources spent on anything other than simple survival, and vice versa. Consequently, he concludes that there is no foreseeable technical solution to increasing both human populations and their standard of living on a finite planet.

From this point, Hardin switches to non-technical or resource management solutions to population and resource problems. As a means of illustrating these, he introduces a hypothetical example of a pasture shared by local herders. The herders are assumed to wish to maximise their yield, and so will increase their herd size whenever possible. The utility of each additional animal has both a positive and negative component:

Positive : the herder receives all of the proceeds from each additional animal
Negative : the pasture is slightly degraded by each additional animal

Crucially, the division of these components is unequal: the individual herder gains all of the advantage, but the disadvantage is shared between all herders using the pasture. Consequently, for an individual herder weighing up these utilities, the rational course of action is to add an extra animal. And another, and another. However, since all herders reach the same conclusion, overgrazing and degradation of the pasture is its long-term fate. Nonetheless, the rational response for an individual remains the same at every stage, since the gain is always greater to an individual than the distributed cost is. The overgrazing cost here is an example of an externality.

Because this sequence of events follows predictably from the behaviour of the individuals concerned, Hardin describes it as a tragedy: "the remorseless working of things" (in the sense described by the philosopher Alfred Whitehead).

In the course of his essay, Hardin develops the theme, drawing in examples of latter day "commons", such as the atmosphere, oceans, rivers, fish stocks, National Parks, advertising and even parking meters. A major theme running throughout the essay is the growth of human populations, with the Earth's resources being a general commons (given that it concerns the addition of extra "animals", it is the closest to his original analogy).

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