Plate i in print

The Pasture

Hardin's tragedy: how a pasture open to all is grazed to ruin, each herdsman gaining the whole of his beast and bearing only a sliver of the cost, till the field that feeds all feeds none.

Picture a pasture open to all. Each herdsman, gaining the whole of every beast he adds and bearing but a share of the ruin they together work, adds without end; and the liberty each takes in the common field is the undoing of them all.

— the tragedy of this plate, after Garrett Hardin, 1968

The last of the failures begins on a pasture open to all, where any man may graze his cattle. The land will bear only so many beasts before the grass is gone; but no one owns it, and no one can be kept off it, and so the question each herdsman faces is not what the pasture can bear but what he, himself, should do. The answer that ruins them all is the answer each, reasoning for himself, will give.

The reasoning is simple, and was set out in its bleakest form by Garrett Hardin, who borrowed the pasture from a forgotten Victorian pamphlet. Consider, says the herdsman, adding one more animal to my herd. The gain from that animal — its sale, its milk — is wholly mine. The cost — a little more crowding, a little more wear on the common grass — is not mine alone but shared among all who graze here, and so falls on me only in part. The gain being whole and the cost being fractional, the balance for me is positive: I add the beast. But every herdsman reasons the same, and so every herdsman adds, and adds again, each pocketing the whole of his gain and shunting most of his cost onto the others — until the pasture, loaded far past what it can bear, is grazed to ruin, and the cattle starve on the bared ground. Each acted rationally; together they were destroyed.1

1. Garrett Hardin, "The Tragedy of the Commons" (1968), drawing on a parable of William Forster Lloyd (1833): each user of an open pasture captures the full benefit of an added animal but bears only a fraction of the overgrazing cost, so each adds until the resource collapses. Freedom of access, through individually rational use, compounds into collective ruin.

What makes the pasture a commons, and not merely a thing badly run, is a pair of properties worth naming exactly, for they recur in every case the volume treats. The grass is rival: the blade one beast eats is gone, denied to the next, so that one user's taking subtracts from what remains for all. And the pasture is non-excludable: no one owns it, no fence rings it, and so no user can be barred. Rival and non-excludable together — this is the common-pool resource, the commons proper, and it is the conjunction that dooms it. Were the grass non-rival, one beast's grazing would leave as much for the next, and crowding would not bite. Were the pasture excludable, an owner could charge for entry, or limit it, and ration the grass as a scarce thing should be rationed. It is because the grass is depleted by use, yet the using cannot be controlled, that the stampede runs unchecked.2

2. The commons is defined by two properties: rivalry (one user's consumption subtracts from others' — the grass eaten is gone) and non-excludability (users cannot be barred — no fence, no owner). Their conjunction (the "common-pool resource") produces the tragedy: rivalry makes overuse costly, non-excludability makes it uncontrollable. Relax either and the problem eases. The full taxonomy of goods by rivalry and excludability appears in The Club.
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Once the structure is seen, the pasture is found to be a figure for a vast share of the world's most pressing troubles. The fishery is a commons: each boat that nets a ton of cod gains the whole of its catch and bears only a fraction of the resulting scarcity, so the fleet fishes the stock to collapse. The aquifer is a commons: each farmer who pumps the shared groundwater draws down a level all must share, and the water table falls toward exhaustion. The clean air and the stable climate are commons: each emitter enjoys the whole benefit of burning and bears only a sliver of the warming, so the atmosphere fills with carbon. The forest, the grazing range, the antibiotic whose power every overuse erodes, the very quiet of a shared street — all are commons, all rival and unowned, and all subject to the same remorseless arithmetic by which the sum of sensible private choices is collective catastrophe. The tragedy of the commons is not a quaint tale of cattle; it is the structure of the gravest problems our species has made for itself.3

3. The structure is pervasive: fisheries (overfishing to collapse), aquifers (groundwater depletion), the atmosphere and climate (carbon as a shared sink), forests, rangeland, antibiotic effectiveness, and congestion are all common-pool resources, exhibiting the same tragedy — private benefit whole, social cost shared — at scales from the village pasture to the planet. The global cases return in The Planet.

It is worth naming the deep form of the trap, for it is not peculiar to pastures but a structure the theory of games treats in its own right. The herdsman's situation is a prisoner's dilemma writ for many players. Each does better, whatever the others do, by grazing one more beast — restraint is his dominated strategy, overgrazing his dominant one — and so all, pursuing their dominant strategies, arrive together at the outcome all would least have chosen, the ruined pasture, when collective restraint would have left every one of them better off. The tragedy is not a failure of reason but its product: it is precisely because each reasons well, for himself, that all fare badly, together. This is what marks the commons as a failure of the market and not of the men in it — the incentives, not the characters, drive the ruin — and it is why the mere plea that each restrain himself breaks against the rock of private interest: the herdsman who alone holds back merely cedes the grass to those who do not.4

4. The tragedy is a many-person prisoner's dilemma: overuse is each user's dominant strategy (better whatever others do), so all reach the collectively worst outcome though mutual restraint would benefit everyone. The failure is structural, driven by incentives, not character — so moral exhortation alone fails, since a lone restrainer only yields the resource to the unrestrained. The game-theoretic foundation returns in The Sanction.

If the ruin flows from a structure — gain whole, cost shared, use uncontrollable — the cure must somehow alter the structure, must make each user feel the cost his taking imposes on all. Two ways to do this have long seemed the only ways, and between them the argument over the commons ran for a century. The first is to set a power above the users — the state, which by quota and rule and penalty commands what each may take, supplying from outside the restraint the users will not impose from within. The second is to divide the commons among the users as private property — to fence it, so that each, now owning his parcel and bearing the whole cost of his own overuse, restrains himself as a sole owner would. Regulate, or privatize; the Leviathan, or the fence. But the parable, having posed the tragedy, quietly forecloses a third answer that the volume's flagship will reopen — and the volume's question is the one Hardin's herdsman makes us ask: why is the shared meadow always overgrazed, and need it be?5

5. The two orthodox cures: state regulation (quotas, rules, penalties imposed from above — see The Leviathan) and privatization (dividing the commons into private parcels, each owner internalizing the full cost — see The Enclosure). Both concede the price's failure and impose a solution from outside the community. The flagship, The Covenant, reopens a third possibility the dichotomy obscured.

The pasture, then, is the tragedy in its oldest dress: a thing rival and unowned, taken by each to the ruin of all, not from malice but from the plain arithmetic of a gain kept whole and a cost shared out. It is the last of the failures because it is the most collective — not one party hiding from another, nor a cost stranded on a bystander, but every user burdening every other, all at once, in a trap each reasons his way into. The plates that follow trace the tragedy's mirror, the public good that the same arithmetic leaves unbuilt; the logic of collective action that underlies them both; and the two cures, command and enclosure, that the age proposed — before the flagship returns to the herdsman's despairing question and finds, against the parable, that the meadow need not be overgrazed after all. The next plate turns the commons inside out, from a shared thing overused to a shared thing never made: the lighthouse no merchant will build, though every ship would bless it.