Tragedy of the commons
The tragedy of the commons is a metaphor that illustrates what some observers may believe to be sub-optimal use or even destruction of public or other collectively shared resources (the "commons") by private interests when the best strategy for individuals conflicts with the common good. The metaphor is often used to argue in favour of private property and against theories such as libertarian socialism which aim at communal ownership of resources. The term was popularized by Garrett Hardin in his 1968 Science article "The Tragedy of the Commons."
The key to the tragedy of the commons is that when individuals use a public good, they do not bear the entire cost of their several actions. Each seeks to maximize individual utility, and so ignores costs borne by others. This is an example of an externality. The best (non-cooperative) strategy for an individual is to try to exploit more than his or her share of public resources. Since every rational individual will follow this strategy, the theory goes, the public resource gets overexploited.
Historical background
The originating metaphor is of a "common", which was not public land — the public at large had very limited rights, and only those locals who were also "commoners" had access to a bundle of rights; each commoner then had an interest in his or her own rights, but the common itself was not property, nor were the rights "property" since they could not be traded. In a traditional village these provided commoners with rights of grazing, gathering fuel wood non-destructively "by hook or by crook", etc. (the form "commons" is plural, and refers to the whole group of commons subject to these effects).
Consider an area used for grazing (among other purposes — it could be "Lammas Land", used for private crops in season) that can support 50 cattle indefinitely, a population of 25 peasant householders who keep cattle among a range of subsistence activities, and that each peasant can advantageously graze and profit from 2 cattle indefinitely. By grazing one extra cow, a peasant can make roughly 1/2 extra "profit" at a "cost" of only 1/50. However this was typically a subsistence activity, not a commercial one, so it is misleading to think in terms of "profit" and "cost"; keeping sheep would have been a more commercial activity, not typical of peasant life then. Thus each peasant is logically tempted to keep adding cattle beyond the capacity of the common to sustain them all optimally. In this example, the carrying capacity and potential yield of the land were not destroyed.
However, the metaphor is not an accurate description of how the system worked during most of its history, although it serves here for purposes of illustration. Historically, no single common was ever truly public but was reserved for its own commoners, whose own use was also restricted in various customary ways (which differed from place to place). The system indeed began to behave in the ways described, but that was not its standard mode of operation but rather a late response to internal and external stresses, e.g. from demographic and cultural shifts.
Modern equivalents
Modern equivalents are pollution of waterways, logging of forests, overfishing of the oceans, tossing of trash out of automobile windows, and e-mail spamming. The contribution of each actor is minute, but summed over all actors, these actions degrade the resource.
Another example would be hoarding supplies of an essential item during a shortage. Let's say that all our tap water gets poisoned, somehow, and everyone has to rely on bottled water from supermarkets. Rationally, each person knows that they should limit their purchases of bottled water for the period of the shortage (ie, they should 'co-operate'), because if everybody rushes to the supermarket and stocks up on water (ie, if they 'defect') supplies will quickly run out — so that, in the long-run, there will be nothing left for anyone. However, each person also fears that hoarding is precisely what everybody else will be doing; therefore, rationally, they know that if they are to be sure of securing any supply of water at all they had better go and stock up too.
Attempts to solve the 'tragedy'
The tragedy of the commons can be seen as a collective prisoner's dilemma. Individuals within a group have two options: cooperate with the group or defect from the group. Cooperation happens when individuals agree to protect a common resource to avoid the tragedy. By cooperating, every individual agrees not to seek more than their share. Defection happens when an individual realizes that it is in their interest to use more than their share of public resource.
One of the leading problems of political philosophy is to articulate a solution to the tragedy of the commons. Typically, a solution involves enforcement of conservation measures by an authority, which may be an outside agency or selected by the resource users themselves, who agree to cooperate to conserve the resource. Another commonly-proposed solution is to convert each common into private property, giving the owner of each an incentive to enforce its sustainability. Effectively, this is what took place in the English "Enclosure of the Commons"; this case highlights the effects of hidden wealth transfer in privatization, if no or inadequate matching compensation occurs.
A popular solution to the problem is the "Coasian" one.
Digital commons
Many people argue that the 'tragedy of the commons' principle does not apply to certain aspects of the digital world, because sharing information and software with other people does not decrease the amount that is available for others. Indeed, as the writer Eric S. Raymond, in an essay called The Magic Cauldron [1] has pointed out, in the case of open source software more widespread use actually tends to increase the usefulness of a product — the more people that are finding and correcting bugs, the better it is for everybody. Raymond has described this process as the inverse commons (see also: network effect). A similar process may be observed in collaborative, open content projects like the Wikipedia encyclopedia.
See also
External links and references
- The original article and responses to it From the Science Magazine website.
- "Global Tragedy of the Commons at COP 6" by John Hickman and Sarah Bartlett
- Government Meters On Private Water Wells -- concrete contemporary example
- What about the "Tragedy of the Commons"? Surely communal ownership will lead to overuse and environmental destruction? -- Libertarian Socialist critique of the "Tragedy of the Commons"