Tragedy Of The Commons

or Why can Communism never succeed in RealLife.

The name of an essay on overpopulation by Garret Hardin.


A commons, that is, a shared or unowned resource, is used inefficiently (a lake being overfished to exhaustion, for example, or being used as a dump for toxic chemicals) because no one has any incentive to do otherwise.


The phrase is actually not commonly used by economists, who more often would describe a tragedy of the commons situation as an externality. Economists have long known that externalities can be ameliorated in several ways, including by making the commons a private good ("internalizing the externality") or by governing the externality through collective action (taxation, permits, ...). Which method is best depends on the situation and often the ideology of the person doing the analysis; it is known that when there are no transaction costs, privatizing the commons leads to an efficient outcome (this is Coase's Theorem).

But privatising can earn the ire of people whose commoners' rights are no longer respected.

The law locks up the man or woman
Who steals the goose from off the common
But leaves the greater villain loose
Who steals the common from under the goose.
(from 17th century anti-enclosure protests in England)

Application to Wikis

For discussions for whether a tragedy of the commons situation applies to Wikis such as this one, please see TragedyOfTheCommonsCantHappenHere; also, ComedyOfTheCommons.


Hardin's essay is problematic. See, for some discussion of why. In summary, he is using historically inaccurate 'evidence' to lend spurious credence to his thesis (which is also problematic, being overly simple, which is not to say useless).

Applying Policies and Excercising Controls

Modern British commons operate under a wide range of policies explained at . There are none that permit unrestricted use; most are controlled by small communities, which circumstance acts to render the modern British system innaccessible to the classic tragedy distinguished by Hardin. It's not without its own brand of tragedy however; the uncontrolled spread of disease vectors through Britain's extensive common lands is one of the factors implicated in the rapid spread of hoof and mouth there.

Economic Definition - Any Shared Resource

To economists, a Commons is any shared resource. The tragedy of the commons occurs when it is despoiled by over-utilization or abuse. This tragedy, of course, occurs in a great many other development contexts too.

Historically, a "Common" was a big patch of grass shared by a village. Villagers would graze sheep and cattle, or grow small market gardens there. These different uses interfere. Moreover, the more animals grazed on the Commons, the more its soil is compacted and eroded. This is obvious to everyone, but there's nothing anyone individually can do about it.

That's the tragedy: your best move as a villager is always down the path of eventual destruction of the Common, even though it's obvious that that's going to happen.

Collective Management

This is absent of effective collective action, of course. A TragedyOfTheCommons situation is an argument for acting together (e.g. setting a quota of sheep per villager, or per household; selling sheep medallions to make sure you can never catch a sheep when it's raining out, etc.).

In a village setting, such collective management is relatively easy to organize. On larger scales, and within corporate settings, however, humans have proved unable or unwilling to prevent such tragedies. Best recent example is the collapse of the world's fisheries.

Demonstrated via Games

There are some theoretical games in which everyone's best move considered individually turns out to be bad for everyone individually. There is good reason to think these games get instantiated in the real world. It's kind of important to recognize these instantiations, so you can take some collective action before you end up in a bad situation.

but if your best move is bad for everyone - its therefore bad for you (whether immediately, or because it reduces future good moves); and therefore cant be your best move.. the problem then reduces to achieving a true understanding what your actual best move is ... -- JaysenNaidoo

I know that usually, one would say that "everyone's best move individually turns out to be bad for everyone collectively" - there are many phenomena in which this is true. But this includes cases where some people actually gain individually, even if collectively, everyone is worse off. A very simple example would be passing around a plate of cookies with the rule that you can take one cookie or two cookies, but as soon as someone takes two cookies, nobody else gets any cookies (and those who already have a cookie have to give it back). If I take two cookies, it's obviously worse collectively (two cookies, N people vs N cookies, N people). But it's still better for me individually - I have two cookies, as opposed to one.

Even More

But the TragedyOfTheCommons is even worse than that: the tragic outcome is not only worse collectively (all of us together have less), it's worse individually (each one of us has less, with no exceptions). To translate it into cookies: every day the plate of cookies is passed around, and we each take as many as we want. The next day, the plate is replenished to its original level of cookies. But if the plate of cookies is ever emptied, it never gets passed around again. -- GeorgePaci

Destruction of Renewal Capacity

The reason it comes up is that biological resources tend to create the "commons" problem - any resource that grows proportional to it's unharvested size will produce this behaviour. Be it fish, trees, etc. Consumers rush to harvest as much as they can, because other consumers will deplete the resource and leave nothing... but if they had collectively held off, they would each individually have accrued more harvest in the long run. Resources that deteriorate in captivity are similar - imagine an oil well, where all oil stores are leaky - if each consumer drew from the oil well as they needed oil, they would each individually get more in the long run than if they all grabbed as much as they could up front and stored it for later... but because the oil well is being depleted by other consumers, they must grab it now (despite the wastefulness) or else miss out on their share.

Actually, one can be even more generic. A commons is any shared resource that provides more benefit to each individual user while it is in the commons than it does when harvested exploitively (as opposed to sustainably). It happens at its worst when it is possible for the most exploitive users (which are a small subset of all users) to accrue more benefit from it than they would if it were a shared resource. Even if they don't actually receive this benefit, the possibility will drive them to start the cycle of "it's being destroyed anyways, I'd better get my share while I can".

Examples: SUVs, Fisheries, and Sheep


Examples: driving SUVs. All the soccer moms want to be high up, so as to see over the traffic. The problem, of course, is that it's not possible for everyone to be higher than everyone else. The solution: make people ashamed of acting fearfully. Honour is not possible without courage. To be honourable is to act assuming that the other party will also be honorable.


Imho, the best example is fisheries. If not overfished, they can provide a middling amount of fish to each fisherman in perpetuity, as the stocks are self-regenerating. However, a fisherman can also take a large amount of fish for himself. If he does so, he will get more fish and be better for it, although he does damage to the stocks and removes long term viability. If nobody else was overfishing, the logical move is to fish in moderation - it maintains the perpetuity of the stocks. However, once others start overfishing, there is no disincentive to overfish - the stocks will be damaged, and the fish will cease regenerating. So the fisherman is faced with the option of (a) fish moderately, or (b) overfish. (b) provides him with more fish, and (a) has negligible benefit - the fish stocks will vanish and he will have gotten less fish. And the point is that every single person did what was in their own best interests, which produced an individual outcome that was worse than every single person acting in a collective manner. Depleted stocks sucks for every single fisherman - but fishing moderately when the stocks are being overfished by others is equally pointless. And remember, the first fisherman's overfishing had only minimal impact, so it was still in his best interests - he gets more fish, and the fishery will still produce for others.

Sheep, Farmers and Commons Grazing

Lest the basic point gets lost in the analysis... I think the key thing about a TragedyOfTheCommons is that a single farmer *does* in fact gain incremental benefit by grazing one more sheep on the commons -- but *only* if they assume that the other farmers are going to act stupidly/selfishly.

That is, each extra sheep decreases the overall quality of the grass, so obviously (at a certain point) it is suboptimal (for all the farmers collectively) to graze another sheep. And, yes, less obviously, it is also suboptimal for the individual farmer to graze another sheep -- if they assume that other farmers act in a similarly enlightened way.

But the basic point is that the quality of the grass is primarly a function of the efforts of the farmers overall, and if there is a lot of farmers overall, an individual farmer may feel that he does not have a lot of effect on that - ie "they're all gonna do it anyway so I may as well get mine".

The tragedy is that if the individual farmer assumes the other farmers will act stupidly/selfishly then grazing one more sheep will in fact accrue more benefit to him than not (ie his sheeps gets the last of the grass). The GoodNews is that if he is enlightened enough to see that others may calculate and act 'like him' then, at some point its better for his own purely selfish interests not to graze another sheep.

Also, its worth noting that in my mind this doesn't have a lot to do with historical village commons, or sheep - rather the whole thing is a good metaphor for a complex scenario that occurs all too often. The best real world example is probably over fishing.

-- MilesThompson

(As originally mentioned later in the page, this is a classic example of the PrisonersDilemma)


In general, any "looting" pattern can be thought of as the "tragedy of the commons".

Obvious Solutions

There is an obvious solution to the TragedyOfTheCommons problem. Make the common a property of one owner which will control the valuable resource. To own something obligates. (AntoineDeSaintExupery). So, even though the individualistic action may be unfair, it will not be suicidal. Usurp it, or let them destroy it. -- GregorRayman

Damn, that's a nasty philosophy. Let them destroy it and have natural selection find a group to take their place that will do a better job. -- AndyPierce

It is also the solution that Economists like to recommend. For instance, divide the supportable amount of pollution that factories can support into pollution credits, give equal amounts to each, and then let each company decide whether it is cheaper for them to clean up their act and sell credits or else buy credits from someone else.

This falls apart in practice when the transaction cost of keeping track of who owns what outweighs the benefit to the owner of managing that resource. What I consider a good example of this is described at on page 31 where the cost of tracking down who owned copyright on publications from the 1920's and 1930's was a dozen hours of work per document. And this underestimates the cost since they only tried this when they thought it would be relatively easy.

-- BenTilly

I wrote about some research I did in a message with the title "Beyond the Tragedy of the Commons". The basic point is that there have been many examples of successfully managed commons over time, and that externally-imposed "solutions", whether capitalist, communist, fascist, ... almost always degrade both the commons and the community that used to manage it.

-- DonDwiggins

Punish Abusers

The Commons works best if it is possible for individuals to "punish" abusers. Odds are that if the guy taking 2 cookies is taken to the garden shed for a quiet chat by some of the others who had no cookie, he will only take 1 cookie the next time. And when the news spreads, so will the other. Now read me right, I'm not advocating that the "punishment" must be physical even if in some cases it is. More common is that you are more or less "frozen out". You are not invited to happenings and if you ask for a favor, it is not granted. That kind of social control works best in geographically small communities. If someone gets powerfull enough so he can safely ignore the threat for punishment, then the Commons are doomed. -- Anders C

Who makes the cookies?

Just an example from the beginning of the page. I suppose the person who made the cookies invented the stupid rules too. Probably it was someone who wants to publish a paper on social behaviour. ;-) -- Anders C

Well, in a democratic country the cookies are made by bakers. And the government takes some 40% of the cookies to make it to the Commons. So doomed are the bakers, the Commons will survive .-)


First, the singular noun for the piece of land shared by a village is common, not commons. The plural is commons. Since this is my first post to Wiki I'll let someone else edit the entire page to reflect this.

Second, and relevant to the question of whether the tragedy of the commons actually happens in reality, many of these commons still survive in London, despite it now being the largest city in Europe, and they are still called commons: Wimbledon Common, Mitcham Common, Clapham Common, and many more.

Another point, is that yes, there are many fine parkland areas in London called XXXXX Common (I remember with particular fondness living near Clapham Common) but sadly they aren't commons anymore, except in name. Just try grazing your sheep there or planting potatoes ;-) Indeed, the byelaws that are displayed at the entrance to every "common" explicitly forbid such activities.


An observation: all of the commons (at least in Britain and France and I suspect many other European countries) are now privately owned, albeit by the local authorities. The elected local officials administer the common using money raised from taxation; however, legally, the "commons" are the property of the local authority. You could argue that these communally owned areas are still just that, but the reallity of the situation is that these pieces of land are now privately owned by the local authority.


Many commons have long been owned by individuals. Those with property adjacent to (or on) the common had "commoners' rights". Those rights were the right to collect wood, graze sheep etc. The right goes to the owner of the property, not to the individual. You move, you lose the rights. In the 1960s people (in the UK) had to reapply to assert their commoners' rights. Many did not and the rights lapsed. Which is why I can't graze sheep on the common adjacent to me; the previous owners let the right lapse. Good job I don't have any sheep then.

A democratically elected council is not a private entity.

In these circumstances, the TragedyOfTheCommons has been averted by privatisation of the resource. Hence these pieces of land are not good examples for use as a basis of discussion.

The true "commons" of the modern world are those areas that fall outside of the control of a single person, organisation, or country. The world's oceans are a good example.

Success by Cooperation

Maybe the whole point is "the individual" vs. "the collectivity". Maybe all people are really one, so individual profit is really an illusion. Or maybe all people and all the pastures and sheep are all one. I can't think about TragedyOfTheCommons happening inside my own body, where the liver gets to say: "A-Ha-Ha-Ha I get More Blood than any other organ!!" ?? -- FabioCecin

The beauty of evolution is that greedy competitiveness can evolve into cooperation (as in the liver example). However, that's not always the case. When separate individuals (with different genomes) are concerned, greediness may sometimes be the best strategy. It depends on the payoffs and the strategies of the other individuals. See PrisonersDilemma for more on how this works.

Policing Scarce Resources

I see that, after the initial mention of "overpopulation", it was quickly abandoned in favour of a discussion on how to police scarce resources. What is important about over-farming of a renewable resource due to overpopulation is that the resource is scarce (i.e.: the surplus beyond what is needed to allow continued replenishment is limited), and that someone is going to have to go without -- and you know it won't be the appointed manager of said resource. There are only two solutions to scarcity: fewer consumers or more product that fits the same need (I'm assuming that the need is really a need, i.e. necessary for survival, and that the consumers can't simply make do without). Nature will happily take care of thinning out the consumers. It is the choice/fortune of human beings to seek ways to increase the amount of a resource, although limiting/reducing growth of the consumer population is a high priority when too many resources become scarce or cannot replenish themselves.

Individual vs collective: this is a subjective attitude, which does not do much to explain the way systems change, only the way people "feel" about the changes. Your bodily organs don't compete because they are part of a balanced system, but if you decide to starve yourself, watch as the various parts of your body begin to compete for the limited calories. It's no fun waiting to see which organ fails first. You'll notice that low priority systems like muscles are deprived before the organs.

There is no scarcity of wiki, or any other type of information, for that matter, unless it is artificially imposed by copyright. -- Brent

How do we apply this analogy to software development? In a team environment with a set of library classes that are used by everyone but are unknowned by any team or team memeber, it's not clear that the problem will occur. Every one has incentive to make sure the code works well for its intended purpose. No one has incentive to contribute to it rotting.


The problem with the common library in my experience, is that if no one "owns" it it will rarely get any updates or fixes. Problems with the library are instead fixed in the individual applications that use it, by whatever sneakiness the language allows, when faced with making the same changes again in the common library and making sure said changes are acceptable to everyone, most developers will throw up their hands and say, "Not my problem."

this would lead to the common library freezing with bugs intact, but not actually degrading further so isn't a 'tragedy of the commons'

Reducing Headcount

I see the problem, as with almost everything in life, as being too many people. More people means more individual anonymity and therefore less individual responsibility. If there are two people in an elevator, no one will fart because it will be known who did it. Put three in an elevator... you can get away with it because of reasonable doubt. And so, once again I am hard pressed to think of a problem that can not be solved by reducing the head count.

Future Discounting

I severely miss a reference to FutureDiscounting here. The problem is not, that the farmers are too stupid to see, that in the future there might no common any more. It's that they value it just very low. The small benefit of letting the sheep eat the grass now is higher than the cost it incurs in the indeterminate future (when they may be dead a long time). Maybe their children will suffer from it - but so will all other children. And who says, that a king will have claimed or invaders have raided the commons by then. From an evolutionary psychology point of view, it is quite sensible to do FutureDiscounting. -- GunnarZarncke

ThomasMore's Utopia was in part about the TragedyOfTheCommons.

The office refrigerator is a perfect example. So many people will leave food in there indefinitely rotting away, not caring or counting on someone else to clean up after them. Notice this does not happen with the office coffee machine since most people derive daily personal benefit from it.

This is a false analogy. Were it not for someone else providing the coffee, the filters, et. al., most people would resort to bringing in their own coffee machines.

Thus, if you want to offer a shared resource, you must provide a steward for that resource in order to enforce proper sharing. In the absence of a steward, you must resort to private property. There can be no compromises.

See and the write-up at our sister site (click icon below). Both are worth reading.

See WhyWikiWorksNot, WikiMindWipe, TragedyOfTheCommonsCantHappenHere, TragedyOfTheCommonsHappenedHere, FutureDiscounting


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