This year marks the 40th anniversary of the publication of Garrett Hardin's extremely influential essay "The Tragedy of the Commons."

Hardin's argument was, essentially, this: Human beings are naturally selfish, and therefore when a resource is held as a pure commons, meaning everyone has the right to use it and no one has the right to exclude anyone else from doing so, human nature ensures that the resource will be over-exploited, in the sense that it will be exploited at a rate greater than that which is best for the community as a whole.

For example, suppose that a community of animal herders uses a certain pastureland as a commons. Each individual herder gets to keep the benefits of grazing another animal, while the community as a whole absorbs the costs of increased grazing.

Hardin points out that, assuming people are selfish -- or, as economists like to call it, "rational maximizers of their own utility" -- each individual herder will gain a large benefit from adding an animal, even when that benefit is smaller than the overall cost to the community of degrading the pasture through increased grazing.

The tragedy of this circumstance is that, absent the introduction of some other factor, the perverse logic of the situation guarantees overexploitation of the resource, because what is in any particular individual's best interest in regard to the resource conflicts with what's best for the community.

Hardin's essay has been much-cited by people who advocate transforming public resources into private ones because private property owners are forced to take into account the future costs of resource use, as well as the benefit to themselves, and by people advocating aggressive government regulation of public resources, particularly those, such as clean air or the ocean's fisheries, that are difficult or impossible to privatize.

If Hardin were alive today -- he and his wife committed suicide together five years ago-- it would be interesting to get his reaction to the remarkable success of the Wikipedia project.

Wikipedia appears to be the precise reverse of the Tragedy of the Commons -- a collectively-maintained and "owned" resource that produces huge benefits to its community of users, while all the costs are borne by a small number of individuals. An online encyclopedia that can be edited by anyone, Wikipedia is constantly improving in quality, because the sum of its editing process is positive over time.

This is the case even though it's estimated that fewer than 2 percent of Wikipedia's users ever edit (let alone create) an article. Even more strikingly, the vast majority of article creation and editing is done by a small subset of this much smaller group.

Thus the costs of creating and maintaining this collective resource are borne by a few, while the benefits are enjoyed by people who, in the vast majority of cases, contribute nothing to the enterprise themselves.

In his new book "Here Comes Everybody," NYU professor Clay Shirky asks the obvious question: given the way the process of creating and maintaining Wikipedia distributes its costs and benefits, why hasn't it been destroyed by free riding and vandalism, like an over-grazed pasture or the north Atlantic cod population?

The answer, he says, is that the project is like Japan's Ise Shrine, which for more than 1,300 years has been torn down and rebuilt from scratch in every generation by the Shinto priests who maintain it. They have now done so 61 times.

"Wikipedia," Shirky notes, "is a Shinto shrine; it exists not as an edifice but as an act of love. Like the Ise Shrine, Wikipedia exists because enough people love it and, more important, love one another in its context."

All of which is to say, I suppose, that selfishness is no more inevitable than love.

(Paul Campos is a law professor at the University of Colorado and can be reached at Paul.Campos(at)Colorado.edu.)

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