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Excerpt from ["The Tragedy of the Commons," Garrett Hardin, Science, 162(1968):1243-1248]:

The tragedy of the commons develops in this way. Picture a pasture open to all [ed: a GlobalResource]. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land. Finally, however, comes the day of reckoning, that is, the day when the long-desired goal of social stability becomes a reality. At this point, the inherent logic of the commons remorselessly generates tragedy.

As a rational being, each herdsman seeks to maximize his gain. Explicitly or implicitly, more or less consciously, he asks, "What is the utility to me of adding one more animal to my herd?" This utility has one negative and one positive component.

Adding together the component partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to his herd. And another.... But this is the conclusion reached by each and every rational herdsman sharing a commons. Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit -- in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.

See also


There are two resulting courses of action in a capitalistic/materialistic society. Keep in mind that a free market economy is based on unbounded growth.

The first is obvious: total devastation. We have the Sahara Desert, the result of goat herders slowly eating up the grasslands. This kind of useless devastation could probably be seen in several African countries today.

The second is less obvious. The young, bright grain farmer discovers how to cultivate grass that the sheep will eat. In return for his services, he must be fed with the products of the cattle. This is the entrepreneurial solution.

The latter solution can be evidenced today with such things as the new field of environmental engineering, hybrid gas-electric cars, green products, etc.

However, in order to have the second (capitalistic) solution, everyone must be aware that there is a better way. This requires education and communication.

Another solution is to bring all the herdsman under the wing of one power. This requires a PoliceForce, and is very expensive. The advantage is the ability to control people's actions through violence. This is how we control the fisheries in Canada. You have to acquire a license. Fishing excessively puts you in front of the judicial system. The judicial system is empowered (at the extreme bottom) by the weapons of the police.

Now, online, you automatically control access to the commons anyway as it is on your server. You don't need to use a PoliceForce. This allows either a TechnologySolution or a CommunitySolution (or even a LegalSolution because you can uniquely identify people if you so choose) without the need for either capitalism or totalitarianism.

Online communities are not goat herding. Moreover, the pollution has nothing to do with resources (you can back up, move, undo, increase bandwidth, etc.) and everything to do with the community itself. More specifically, the community "flavour," or community life.

A community with strong life will overcome TheTragedyOfTheCommons by banding together to solve the problem. Just look at http://scoop.kuro5hin.org to see this happening. -- SunirShah


There is another factor, that of competition. The herdsman will reason, "If I don't, somebody else will".

A really rational herdsman will anticipate the tragedy. The chaos is not in his long-term interests; if all goats die the "negative component" becomes minus infinity. Many people are smart enough to understand this and be willing to practice self-restraint. However, it does him no good to hold back unless everyone else holds back too. In practice he knows there are cheats. He knows the commons is going to be overgrazed whatever he decides, so he might as well grab his share while he can.

Part of the role of a police force is not to deter me (since I am inclined to self-restraint), but to convince me that you have deterred all the others. Only then does my altruism achieve anything. A fair police force will be much cheaper than an unfair one, because it will rule with the consent of the population.


The Tragedy of the Commons was formulated by GarrettHardin?, human ecologist at the University of California, Santa Barbara, in a 1968 essay, and is the core of his somewhat controversial "Lifeboat Ethics". I attended UCSB in the late 1980s, met Professor Hardin, and read his works extensively.

The Tragedy is frequently misapplied, particularly to online, cyber, and free software situations. While it may be appropriate in some instances of application, it very frequently is not, and even where it is, is invoked without full understanding. There are any number of modern situations to which the reasoning is appropriate, shared computing, networking, transportation, and environmental pollution resources being among them.

TheTragedyOfTheCommons is based on 5 factors:

  1. A common resource. This is a resource which is used in common by several parties.
  2. Rivalrous consumption. The use of the resource by one party means that another party is denied use. Pastureland is an example of a rivalrous good -- capacity used by one herd of cattle is not available to another. Information is non-rivalrous in nature. For distributed data, access to the data by one party doesn't prevent another from accessing it as well. Note that server resources or bandwidth may themselves be rivalrous goods.
  3. A system at its carrying capacity. TheTragedyOfTheCommons only kicks in where a system is already providing its maximum sustainable output. Below this level, increased total output is possible. The tragedy is the paradox of increased personal benefit resulting in decreased social benefit (below). When adding an additional unit of consumption reduces total output, this situation occurs.
  4. Private accrual of benefits. The benefits of consumption accrue to the party consuming them. Cattle, in the classic case. Shared computer resources are another.
  5. Public accrual of costs. The costs of additional benefit are spread over the entire group.

Hardin identifies one solution to the paradox: mutual coercion, mutually agreed on. That is, in a situation where common resources are being utilized at capacity, the group as a whole must device means by which additional use of the resource is restricted. This can be a PoliceForce, taxation, moral suasion, cost/profit sharing, or other means, but it has to exist and be enforceable.

Significantly, the thought that Hardin opens his article with is that there are problems which exist for which there is no technical solution.

But we also have the problem that conscience is self-eliminating

To make such an appeal [to conscience] is to set up a selective system that works toward the elimination of conscience from the race.

Now that would be a tragedy of uncommon proportion, no? -- KarstenSelf


However, in order to have the second (capitalistic) solution, everyone must be aware that there is a better way.
Seems like the awareness among investors is enough. You can invest your money into someone herding on declining commons -- or you can invest your money into supposedly more stable businesses. Your choice? -- NikitaBelenki

Which is probably why one of the assumptions which economists make to justify the so-called free market is infinite access to and frictionless flow of information.


There is another quiet assumption, which undermines the "ruinous" conclusion: It is assumed that the utility of the thousandth cow is the same as the first. This is unrealistic. If you are eating the cows, eventually you become full. If you are selling the cows, eventually the market saturates. Can anyone think of an example where utility does not naturally damp out?

Once you add in the damping assumption, people will not be compelled to add more cows without limit. Eventually, everyone will have five billion cows, there will be cows on top of cows, and all players will say "why bother adding another?". 5 billion cows per person may well be more than would maximize the total utility, depending on the assumptions. However, the final stable state is probably not "ruinous" (though it depends on the assumptions). More importantly, the stable state may or may not be worse than particular attempted solutions.

The linked page uses this model to lead credence to flights of fancy and frankly disturbing policy proposals. It concludes from the model, for example, that humans left alone will reproduce without end -- disregarding that human populations have successfully damped themselves throughout history. It makes excursions into psychology regarding guilt. And it tells us to stop thinking of "coercion" as such a dirty word. Is this model ever used, well, usefully? Accurately? For any purpose besides rationalizing policies that defy common sense? This model appears better as a basis for science fiction, than as a basis for reasoned policy decisions. -- LexSpoon

This "damping assumption" is a basic economic principle called the Law of Diminishing Marginal Utility. I wouldn't say it's the main factor behind population plateaus of humans, however... -- ChuckAdams

TragedyOfTheCommons explains, in exacting details, such diverse phenomena as:

Another possible solution is to interpret The Commons as a contribution-oriented ExtremeOpenBusiness, where all "contributions" are made visible to the public. See PublicGoodsGame. -- FridemarPache


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