The tragedy of the commons is a metaphor used to illustrate the conflict between individual interests and the common good. The term was popularized by Garrett Hardin in his 1968 Science article "The Tragedy of the Commons."
Hardin uses the example of English Commons, shared plots of grassland used in the past by all livestock farmers in a village. Each farmer keeps adding more livestock to graze on the Commons, because it costs him nothing to do so. In a few years, the soil is depleted by overgrazing, the Commons becomes unusable, and the village perishes.
The cause of any tragedy of the commons is that when individuals use a public good, they do not bear the entire cost of their actions. If each seeks to maximize individual utility, he ignores the costs borne by others. This is an example of an externality. The best (non-cooperative) short-term strategy for an individual is to try to exploit more than his share of public resources. Assuming a majority of individuals follow this strategy, the theory goes, the public resource gets overexploited.
The tragedy of the commons is a source of intense controversy, precisely because it is unclear whether individuals will or will not always follow the overexploitation strategy in any given situation. However, experiments have indicated that individuals do tend to behave in this way.
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 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 least until it has 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 include pollution of waterways and the atmosphere, logging of forests, overfishing of the oceans, personal vehicles jamming public roadways, tossing of trash out of automobile windows, poaching and e-mail spamming. The contribution of each actor is minute, but summed over all actors, these actions degrade the resource.
Possible solutions to 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 his share. Defection happens when an individual decides to use more than his share of a public resource.
Game theory shows that cooperation maximizes every individual's benefit in the long run (i.e. the 'tragedy' does not happen, the commons are preserved and can be used indefinitely), while defection maximizes an individual's benefit in the short run at the expense of destroying it in the long run (i.e. the 'tragedy' happens and all individuals lose). Thus, a possible solution to the tragedy of the commons is to simply have a group of far-sighted individuals who can see their long-term interest.
Articulating solutions to the tragedy of the commons is also one of the leading problems of political philosophy. Many such solutions involve 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 frequently-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 also the "Coasian" one.
In Hardin's essay, he proposed that the solution to the problem of overpopulation must be based on "mutual coercion, mutually agreed upon" and result in "relinquishing the freedom to breed." Hardin discussed this topic further in a 1979 book, Managing the Commons, co-written with John A. Baden.
External links and references
Last updated: 06-02-2005 05:21:36