EconomicsCounterintuitive resultDebated★ Famous
The Tragedy of the Commons
Also known as The commons dilemma, Overgrazing problem
Every herder gains by putting one more animal on the shared field. The field is destroyed by people behaving reasonably.
- When
- 1968
- Difficulty
- Intermediate
- Reading time
- 15 min
- People
- Garrett Hardin,Elinor Ostrom
Counterintuitive result. Nothing is wrong with the reasoning. The result is simply correct and human intuition is simply unreliable here. Not a contradiction at all.
Discover
Picture a big green field in the middle of a village. It does not belong to anyone. Everybody's sheep graze on it.
You have ten sheep on the field. So does everyone else. There is just about enough grass.
Now you think: what if I put one more sheep out there?
That extra sheep is entirely yours. Its wool is yours, its lambs are yours. All the good of it comes to you.
The cost is that the field gets a little more crowded and the grass gets a little thinner. But that thinner grass is shared out among every sheep in the village. You bear a tiny sliver of it. Everyone else bears the rest.
One extra sheep: all of the gain, a sliver of the cost. Obviously you add the sheep.
Here is the difficult part. Everyone in the village is standing at the edge of the same field, doing the same sum, and getting the same answer.
Add the sheep. Add another. Add another.
By autumn there is no grass, and everybody's sheep are thin.
Not one person in the village did anything foolish. Every single decision was sensible when it was made. And the field is bare.
Understand
The trap has a precise shape, and once you see it you will see it everywhere.
An action is privately profitable and socially costly, and the person deciding gets the profit while the group pays the cost. In economics the leftover cost is called an externality — a real consequence of your choice that lands outside your accounts.
Nothing in the story depends on greed. It works just as well with a village of kind, thoughtful people. Restraint by one herder does not save the field; it just leaves more grass for whoever is less restrained. That is what makes the situation genuinely hard rather than merely a moral failing. Being good, on its own, does not help. It only helps if everyone else is good too, and nobody can guarantee that from inside their own farmyard.
Garrett Hardin, writing in Science in 1968, put it starkly: "Freedom in a commons brings ruin to all." He argued the outcome was inescapable, and that the only two escapes were to privatise the commons — divide the field into fenced plots, so each person bears their own costs — or to have an outside authority impose limits.
The part Hardin got wrong
He was right about the incentive structure. He was wrong that the outcome is inevitable, and the evidence against him is now overwhelming.
Elinor Ostrom, a political economist at Indiana University, spent decades doing something Hardin never did: she went and looked. She and her collaborators assembled hundreds of case studies of real shared resources — Swiss alpine pastures grazed in common since the thirteenth century, Japanese village forests, irrigation networks in Spain and the Philippines, inshore fisheries in Turkey and Maine, groundwater basins in California.
Many of these had been managed sustainably for centuries. Not by privatisation. Not by a state. By the users themselves, who had built their own rules, their own ways of watching each other, and their own penalties for cheating — and had kept them working across generations.
Some commons do collapse; Ostrom studied failures too, and was careful about them. But the collapse is not a law of nature. It is what happens when the governing arrangements are absent, undermined, or destroyed. Ostrom received the Nobel Memorial Prize in Economic Sciences in 2009 for this work.
Historians added a second correction. Hardin's illustration invokes the English commons, but the actual medieval English and Welsh commons were not open to all. Grazing rights were attached to particular holdings, the number of animals each commoner could pasture was capped — the practice was called stinting — and manor courts enforced the caps and fined violators. The historical example that gave the idea its name was a regulated resource, not a free-for-all. Susan Jane Buck Cox laid out the documentary evidence in 1985 in a paper titled, pointedly, "No Tragedy of the Commons".
The distinction that survives all of this is between a commons, which has identified users and rules, and open access, which has neither. Hardin described open access and called it a commons, and the mislabelling has cost the idea a great deal of accuracy. Ostrom's own view, stated plainly in Science in 1999, was that Hardin's analysis is correct for open-access resources and misleading for everything else.
What Hardin's essay was actually arguing
The pasture occupies about one page. The essay is about human population.
Hardin's thesis is that population growth is a problem with "no technical solution", that the freedom to have children is the freedom that must be withdrawn, and that the mechanism should be "mutual coercion, mutually agreed upon". He wrote that "the freedom to breed is intolerable". These are his central claims, not asides, and they are what the pasture illustration was constructed to support.
Hardin's later writing extended the argument to immigration and famine relief. In "Lifeboat Ethics" (1974) he argued that wealthy nations are lifeboats that must refuse to take on the people in the water, and opposed food aid on the grounds that it would let poor populations grow. He was a founder of, and adviser to, organisations campaigning to restrict immigration to the United States, and wrote of the need to preserve a particular ethnic and cultural character in the population. Scholars who have examined this body of work describe it as nativist and racist; the Southern Poverty Law Center maintains a file on him on that basis.
None of this makes the incentive analysis of a shared pasture false. It is stated here because the 1968 essay is still routinely assigned to students as a neutral piece of ecology, with the pasture excerpted and the argument it was built to serve left out. A reader should know what they are reading.
The shape of it
Same shape, different costume:
Examples
The arithmetic of one extra animal. Ten herders share a pasture, with equal flocks. An animal is worth £100 a year when 100 animals graze, and every animal added beyond that thins the grass enough to knock £1 off the yearly value of every animal on the field. So with $N$ animals grazing, each is worth $200 - N$ pounds.
When a herder adds one animal, they gain that animal's value but lose £1 on each animal they already own. Everyone else simply loses £1 per animal.
| Animals on the field | Each flock | Value per animal | Total village income | Net gain to a herder who adds one more | Cost pushed onto the other nine |
|---|---|---|---|---|---|
| 100 | 10 | £100 | £10,000 | +£89 | −£90 |
| 120 | 12 | £80 | £9,600 | +£67 | −£108 |
| 150 | 15 | £50 | £7,500 | +£34 | −£135 |
| 180 | 18 | £20 | £3,600 | +£1 | −£162 |
| 181 | 18.1 | £19 | £3,439 | −£0.10 | — |
The village's total income is highest at exactly 100 animals — £10,000. Every herder nonetheless has a positive private reason to add animals right up to around 181, where the last column finally turns negative and the adding stops.
At that point the pasture yields £3,439. The village has destroyed roughly two-thirds of its own income, and every single decision along the way was correct. The tragedy is arithmetic, not psychology.
Where it appears, and whether it actually collapsed.
| Shared resource | Individually rational act | Outcome |
|---|---|---|
| North Atlantic cod | Catch one more tonne | Canadian Grand Banks fishery collapsed in 1992; a moratorium put roughly 30,000 people out of work and the stock has still not recovered |
| Atmosphere | Emit one more tonne of CO₂ | Ongoing; the archetypal global open-access resource with no enforcing community |
| Antibiotics | Prescribe for one more borderline case | Rising resistance, a shared resource being depleted prescription by prescription |
| Swiss alpine pastures (Törbel) | Graze one more cow | Did not collapse. Rules dating to a 1483 written charter cap each villager's summer grazing at the number of animals they can overwinter on their own land |
| Spanish huerta irrigation (Valencia) | Take a little more water | Did not collapse. The Tribunal de las Aguas has met weekly outside the cathedral to arbitrate water disputes for roughly a thousand years |
The bottom two rows are the ones missing from most retellings, and they are the reason this entry's status is "debated" rather than "resolved".
Ostrom's eight design principles. Extracted in 1990 from the long-enduring cases, and the most useful practical residue of the entire literature:
- Clearly defined boundaries — who the users are, and where the resource ends.
- Rules fitted to local conditions, not imported wholesale.
- Those affected by the rules can participate in changing them.
- Monitors who are accountable to the users, or are the users themselves.
- Graduated sanctions — a first offence costs little, repeat offences escalate.
- Cheap, accessible conflict-resolution mechanisms.
- Recognition by higher authorities of the community's right to organise.
- For large systems, governance in nested layers.
Principle 5 is the one people find least intuitive and it is among the best supported. Systems that punish a first offence severely tend to break down, because the punishment feels unjust and enforcement stops being applied.
Explore
The three-way disagreement. Hardin's own conclusion was that a commons requires either privatisation or coercive external…
The three-way disagreement. Hardin's own conclusion was that a commons requires either privatisation or coercive external authority. Ostrom's is that a third option — self-governance by the users — is not merely possible but common, and often outperforms the other two because local users hold information that a distant regulator does not. A third position, associated with the property-rights economics of Harold Demsetz, holds that the interesting question is why property rights emerge when they do, and predicts that communities will define rights once the resource becomes valuable enough to be worth the trouble of defining them. These are not merely academic. Which one you hold determines whether you respond to an overfished bay by auctioning quotas, sending inspectors, or funding the fishermen's own cooperative.
Where Hardin's analysis genuinely bites. Ostrom's design principles have prerequisites: a bounded group, repeated interaction, the ability to observe each other, and some authority permitting local rule-making. Take those away and the picture darkens sharply. Deep-sea fisheries in international waters, the atmosphere, and orbital debris are close to pure open access — billions of anonymous users, no boundary, no monitoring, no enforcement. Ostrom herself said so in 1999: the local lessons do not simply scale to global commons, and the scaling problem is unsolved. Anyone citing Ostrom to suggest that climate change will resolve itself through community management is misusing her.
Can the essay be separated from the man? There are two defensible positions and both are held by serious people. One: the incentive structure is a piece of mathematics with no politics in it, and it is legitimate to teach the mechanism while discarding the author. Two: Hardin's framing is not incidental to his politics — the specific choices to define the commons as unregulated, to declare the ruin inevitable, and to conclude that coercion is the only remedy are the choices a eugenicist argument requires, and teaching the frame smuggles in the conclusion. What is not defensible is the common third option of assigning the essay without mentioning any of this.
A note on terminology. Much of the confusion in public discussion of this topic would evaporate if people used "open-access resource" for what Hardin described and reserved "commons" for a resource with a defined community and rules. The field made this distinction decades ago. Popular usage has not followed.
Historical context
1833. William Forster Lloyd, a lecturer in political economy at Oxford, published Two Lectures on the Checks to Population. In it…
1833. William Forster Lloyd, a lecturer in political economy at Oxford, published Two Lectures on the Checks to Population. In it he asks why cattle on a common are "so puny and stunted" and the common itself "so bare-worn" compared with adjacent enclosed fields, and gives the incentive answer. Lloyd's context, like Hardin's, was Malthusian anxiety about population.
1954. The economist H. Scott Gordon published a formal model of the common-property fishery, showing that open-access entry dissipates the entire economic rent of the resource. The mathematics of the tragedy was in the economics literature well before it had a memorable name.
December 1968. Hardin, then professor of human ecology at UC Santa Barbara, published "The Tragedy of the Commons" in Science. It began as his presidential address to the Pacific Division of the American Association for the Advancement of Science. It became one of the most cited papers the journal has ever published, and the phrase entered general English.
1975–1990. Field researchers repeatedly failed to find Hardin's predicted collapse in real common-property regimes. Anthropologists studying inshore fisheries, historians of the English open-field system, and development economists working on irrigation all reported the same thing: the users had rules. In 1985 Susan Jane Buck Cox published the historical rebuttal. In 1986 the US National Research Council convened a panel on common property that gathered much of this evidence in one place.
1990. Elinor Ostrom published Governing the Commons. Its method was what made it decisive: rather than presenting counterexamples, it compared long-lived successes with documented failures and asked what distinguished them, generating the eight design principles as an empirical result rather than a recommendation.
1999. Ostrom, with Burger, Field, Norgaard and Policansky, published "Revisiting the Commons" in Science — the same journal, thirty-one years later — distinguishing open access from common property and posing the global-commons scaling problem.
2009. Ostrom was awarded the Nobel Memorial Prize in Economic Sciences, the first woman to receive it. The prize committee's citation named the challenge to "the conventional wisdom that common property is poorly managed and should be either regulated by central authorities or privatised".
2003–present. Hardin died in 2003. Reassessment of his wider work has intensified since, with a substantial literature examining the relationship between the commons argument and his advocacy on population, immigration and race.
Why it matters
It supplied the default frame for environmental policy for forty years. If ruin is inevitable without ownership or enforcement,…
It supplied the default frame for environmental policy for forty years. If ruin is inevitable without ownership or enforcement, then the policy menu has two items. A great deal of fisheries management, forestry policy and land reform in the second half of the twentieth century was designed on that assumption, and some of it did real damage — nationalising forests in Nepal and parts of Africa dispossessed communities that had been managing them successfully, and in several documented cases the forests deteriorated faster afterwards, because the functioning local institution was destroyed and the replacement state authority could not monitor what the villagers had monitored for free.
Ostrom's correction changed how institutions get designed. The eight design principles are now used directly in fisheries co-management, irrigation projects, community forestry and the governance of digital commons. The practical shift is from asking "who should own this?" to asking "who are the users, can they see each other, and can they make and enforce their own rules?"
It gave the externality a story. Economists had the formal concept of an external cost since Pigou in 1920, but "the tragedy of the commons" is the version that a legislator, a journalist or a fisherman can hold in their head. Concepts travel on their illustrations, which is precisely why the accuracy of the illustration matters.
It is a case study in how ideas get simplified in transmission. A one-page illustration inside a eugenics argument became a stand-alone law of social nature, was refuted empirically by a body of fieldwork that won a Nobel prize, and is still taught in its refuted form. Very few ideas offer such a clean record of the gap between what a field knows and what the public has been told.
Modern relevance
Climate. Greenhouse gas emissions are the closest thing to a true global open-access problem, and it is exactly the case where…
Climate. Greenhouse gas emissions are the closest thing to a true global open-access problem, and it is exactly the case where Ostrom's solutions are hardest to apply: no boundary, no way to exclude, weak monitoring, no shared enforcer. Ostrom's own late work proposed a polycentric response — cities, firms, regions and states acting at many scales at once rather than waiting for a single global agreement — on the grounds that the global commons will never have the single community that the local commons has.
Antibiotic resistance. The most direct medical instance, and one where the Ostrom prescription is actually being applied: hospital antimicrobial stewardship programmes are, structurally, monitoring plus graduated sanctions applied to a bounded community of prescribers.
Groundwater. Aquifers under the US High Plains, northern India and the Central Valley of California are being drawn down by individually rational pumping. Some basins — notably several in southern California — have escaped through negotiated adjudication among pumpers, which is an Ostrom outcome and one she personally studied for her doctorate.
Digital and informational commons. Wikipedia, open-source software and public scientific datasets are shared resources vulnerable to depletion of a different kind: not overuse, but under-contribution and abuse. Their governance arrangements — reputation, graduated blocks, elected arbitration, maintainer hierarchies — were invented independently and map onto Ostrom's principles closely enough that she and Charlotte Hess wrote a book about it.
Orbital debris. Low Earth orbit is a shared resource with rapidly growing use, no property rights, no enforcement, and a physical mechanism for catastrophic collapse in the Kessler syndrome, where debris collisions cascade. It is the newest large commons, and it currently has none of the eight design principles in place.
Free riding on the open web. Web publishers bear the cost of serving crawlers that train models they do not benefit from, and the individually rational response — blocking crawlers, paywalling, poisoning content — degrades the shared corpus that everyone including the publishers draws on. The structure is familiar; the governing institutions do not yet exist.
Sources & further reading
Primary source
(1968)The Tragedy of the CommonsScience, 162(3859), 1243-1248.Science 162(3859), 1243–1248.
The essay that named it. Read the whole thing, not the pasture paragraph.
(1974)Lifeboat Ethics: The Case Against Helping the PoorPsychology Today, 8, 38-43.
Hardin's own extension of the argument to immigration and famine relief.
Book
(1990)Governing the Commons: The Evolution of Institutions for Collective ActionCambridge University Press.
The empirical refutation of the inevitability claim, and the eight design principles.
ISBN 9780521405997
Paper
(1999)Revisiting the Commons: Local Lessons, Global ChallengesScience, 284(5412), 278-282.
Ostrom and colleagues answering Hardin in the journal that published him.
(2010)Beyond Markets and States: Polycentric Governance of Complex Economic SystemsAmerican Economic Review, 100(3), 641-672.
The Nobel lecture, summarising four decades of field and laboratory evidence.
(1985)No Tragedy of the CommonsEnvironmental Ethics, 7(1), 49-61.
The historical case that English commons were regulated, not open access.
How this connects
- Related to
- The Jevons ParadoxTwo ways efficiency fails to save a resource. Jevons shows that using less per unit invites more total use; the commons shows that whoever uses less simply leaves more for the next user.
- The Easterlin ParadoxBoth are arguments that aggregate gains dissolve at the level of the group, and both have been substantially revised by later empirical work that the popular version of the idea has not caught up with.
- Bystander EffectBoth describe how individual rationality produces collective failure. In the tragedy of the commons, each actor consumes shared resources; in the bystander effect, each actor defers helping to others, with the same result — the shared obligation goes unmet.
- Cobra EffectIn the tragedy of the commons, individuals rationally exploit shared resources to collective ruin. In the Cobra Effect, individuals rationally respond to incentives to collective ruin — the structure is identical.
- Goodhart's LawIn both, each actor optimises their own measured payoff and the shared thing everyone depended on is quietly consumed.
- Matthew EffectBoth describe systems where a structural mechanism, rather than individual character, produces a morally troubling outcome. The tragedy of the commons is about over-extraction; the Matthew Effect is about over-attribution of merit.
- Ringelmann EffectBoth describe how individual rational behaviour leads to collective underperformance. The tragedy of the commons is about over-extraction; the Ringelmann Effect is about under-contribution.
- The Abilene ParadoxBoth describe a group outcome that every member would vote against. The commons needs no misunderstanding to produce it, only incentives; Abilene needs no incentives, only misunderstanding.
- The Paradox of ThriftBoth are cases where individually rational actions produce a collective outcome that is worse for everyone — the same fallacy of composition in different economic domains.
- Influenced by
- The Prisoner's DilemmaThe commons is the Prisoner's Dilemma with a hundred players and a pasture. Each herder's extra animal is a defection that pays the herder in full and charges the cost to everybody, so the dominant strategy argument runs unchanged — only the accounting gets bigger.
- Influences
- Braess's ParadoxBraess's paradox is the commons on a road network. Road space is the shared pasture, each driver's route choice is the extra animal, and the surprise is sharper still: enlarging the commons can make the equilibrium worse for everyone rather than better.
Ideas involved
Part of a learning path
- When Groups Decide Badly — step 2 of 5