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 metaphor goes as follows: the Commons is a shared plot of grass land used by all livestock farmers in a village. Each farmer keeps adding more livestock to graze on the Commons, because he does not experience a direct cost for doing so. In a few years, the soil is depleted by overgrazing, the Commons becomes unusable and the village perishes.
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 (e.g. passing drovers could lease grazing for "thistle rent"). 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 themselves "property", since they could not be traded or otherwise disposed of. In a traditional village these rights 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. Thus each peasant is logically tempted to keep adding cattle beyond the capacity of the common to sustain them all optimally. Where the grazing area could sustain 50 cattle indefinitely, this increased grazing load could diminish or even destroy the ability of the land to sustain any cattle, at any rate until it had recovered. (A tragedy of the commons can occur even without complete and permanent destruction of a resource, although such things as overfishing can indeed do that.)
Though this metaphor is not an accurate description of how the system worked during most of its history, 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.
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.
See also
External links and references
- From the Science Magazine website.
- by John Hickman and
