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The tragedy of the commons is a metaphor that illustrates the
sub-optimal use or even destruction of public 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 public resource gets overexploited. A popular solution to the problem is the
"Coasian" one.
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 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.
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.
See also
- tragedy of the anticommons
External links and references
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