Plate viii in print

The Boundary

the deepest turn: that what counts as 'external' is set by where the law draws property, a line that moves as it becomes worth moving — so the price omits not what cannot be priced, but only what no one yet owns.

A right is drawn around a thing when, and only when, the spillover it would tame at last outweighs the cost of drawing it; what lies outside the line is not beyond price, but only not yet worth enclosing.

— the thesis of this plate, after Harold Demsetz, 1967

The volume has surveyed the externality and its cures — the smoke and the silence of the price, Pigou's tax, Coase's bargain, the market in permits. Each cure has taken the same shape: to bring inside the price a cost that fell outside it. The flagship asks the question all this presupposes and never quite states. What is it for a cost to fall outside the price? Where is the edge of the price's ledger, that some costs lie within it and some without — and who, or what, decides where that edge is drawn? The answer overturns the way we have been speaking, and with it the way the failure is usually understood.

We have spoken throughout of costs that escape the price, as though the price were a vessel that leaks — a measure that ought to capture the whole cost of a thing but lets some of it slip through. This picture is wrong, and seeing why is the beginning of the flagship's argument. The price does not leak. It captures, with perfect fidelity, exactly the costs that fall on the parties to the trade — the factory's fuel, the buyer's payment — and it is silent about exactly the costs that fall on everyone else. There is no malfunction in this; it is what a price is. A price is struck between two parties and reflects what those two parties bear; it was never built to carry what third parties bear, any more than a contract between two people binds a third. The smoke is not a cost the price fails to capture; it is a cost that, falling on no party to the bargain, was never the price's to capture at all. The ledger has no holes — it simply has edges, and the smoke lies past them.1

1. The externality is not a leak in the price but a consequence of its nature: a price reflects the costs borne by the parties to the trade and is silent about costs borne by non-parties. Third-party costs were never within the price to escape; they lie beyond its edge by definition. The failure is not a malfunction but a boundary.

If the price's ledger has edges, what determines where they fall? The answer is property. A cost enters someone's reckoning when it falls on something he owns — his fuel, his labor, his land — for then he must be compensated to part with it, and the compensation is a price. A cost stays outside all reckoning when it falls on something no one owns — the common air, the unowned river, the open sky — for then there is no owner to demand compensation, and no price arises. The edge of the price's ledger is exactly the edge of property: what is owned is priced, what is unowned is free, and the externality is precisely the cost that falls on the unowned. The smoke is an externality because no one owns the air. Grant someone the right to the air — let the neighbors own their share of it, or the factory own a license to use it — and the smoke at once acquires a price, for now it falls on something owned, and the owner must be paid. The externality is not a feature of the smoke; it is a feature of the air's unowned condition, and it vanishes the moment the air is owned.2

2. The boundary of the price's ledger coincides with the boundary of property: costs on owned things are priced (the owner must be compensated); costs on unowned things (common air, open sky) are free. An externality is precisely a cost falling on an unowned resource — and assigning ownership internalizes it, converting the externality into a price. This is the form behind Coase's "missing market."
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Here the inversion stands forth, and it is the deepest the family has reached. We take the boundary between the priced and the unpriced — between a thing's cost and its externalities — to be given, a fact of the world: some costs simply are internal, others simply external. But the boundary is not given; it is drawn, by the law of property, and it moves whenever the law moves it. What is an externality today becomes a priced cost tomorrow, the moment a right is defined over the thing it falls upon; what is a priced cost today would become an externality were the right abolished. Harold Demsetz saw the principle behind the movement: a society draws a property right around a thing precisely when the spillovers from leaving it unowned grow costly enough to be worth the trouble of enclosing — when the harm of the unpriced at last exceeds the cost of pricing it. The boundary of the ledger is thus not a natural frontier but an economic one, advancing into the unowned as the unowned becomes too costly to leave free. The externality is not the part of the world that cannot be priced; it is the part of the world we have not yet found it worth our while to own.3

3. The inversion: the boundary between priced costs and externalities is not natural but legal — set by property rights, and movable. Demsetz (1967): property rights emerge to internalize externalities when the gains from doing so exceed the costs of defining and enforcing them. The boundary advances into the unowned as spillovers grow costly enough to be worth enclosing. The externality is the not-yet-worth-owning, not the unpriceable.

This dissolves the volume's question, and answers it. Who pays for the smoke, when the price of the goods does not? The unowned air being no one's, the smoke is borne by whoever happens to stand in it — the neighbors, in their lungs and their wash — and they pay because they have not been given the right to refuse. That is the whole of it: the smoke is paid for by whoever the law has declined to make its owner. And this means the question of who should pay for the smoke is not a question about nature or about fault, as the moral picture supposed, but a question about property — about whom the law shall make the owner of the air: the factory, which may then smoke freely while the neighbors bear it, or the neighbors, who may then charge the factory or forbid it. Coase showed that, where they can bargain, the choice between these does not change how much smoke there is, only who is paid; but where they cannot bargain, the choice of owner decides who suffers the harm outright. Either way, the answer to who pays for the smoke is settled not by the smoke but by the assignment of a right — which is to say, by a choice, made or evaded, about who shall own the air.4

4. The open question answered: the smoke is borne by whoever lacks the property right to the resource it fouls (the air). "Who should pay" is therefore a question of property assignment, not of nature or fault — whom the law makes owner of the air decides who bears or charges for the smoke. With bargaining (Coase), the assignment sets distribution, not the quantity of smoke; without it, the assignment sets who suffers the harm directly.

The answer carries a sting, for it means that the extent of the market — the reach of the price, the line between what is bought and sold and what is suffered for free — is not fixed by economics but chosen by politics, and chosen, often, by evasion. To decline to define a right over the air is not to leave the matter to nature; it is to decide, by default, that the polluter may pollute and the bystander may suffer. To define the right is to decide the opposite. Every externality is thus a question the law has left open, and the leaving-open is itself an answer — usually an answer in favor of whoever benefits from the absence of a price, which is the one who imposes the cost. The boundary of the ledger, drawn by property and movable by law, is therefore a perpetual site of struggle: those who would enclose a harm into the priced world, by defining a right against it, contend with those who profit from its remaining free. The question of what shall be an externality and what a cost is, at bottom, the question of whose interests the structure of property shall serve. The smoke is unpriced because someone prefers it so.5

5. The bite: the extent of the market — what is priced versus suffered freely — is set by political choices about property, and inaction is itself a choice, favoring those who benefit from the absence of a price (the cost-imposer). Every externality is a legal question left open, and where the boundary falls is contested between those who would enclose a harm and those who profit from its remaining free. The failure thus reconnects to distribution and power.
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The careful statement guards against two errors. It is not true that any externality could be cured by simply defining a right and walking away — for where the parties are a scattered multitude, as with the carbon in the sky, no bargain among them is possible, and defining a right, while it may help, cannot by itself summon the market that transaction costs forbid; there the collective hand of tax or rule or constructed permit must act, as the earlier plates showed. Nor is it true that the boundary can be drawn anywhere without cost — defining and enforcing a right is itself expensive, and Demsetz's lesson is precisely that we should enclose only where the harm of leaving free exceeds the cost of enclosing, so that some spillovers are rightly left unpriced, too small to be worth the machinery of ownership. The claim is the exact one: that the line between the priced and the unpriced is a legal and economic artifact, not a natural fact; that it is drawn where enclosure pays and moved as the calculus shifts; and that what we call an externality is the world on the far side of that movable line — sometimes left there wisely, because pricing it would cost more than the harm, and sometimes left there only because those who gain from its being free have prevailed.6

6. The honest edge: defining rights does not always suffice — scattered multitudes (carbon) still require collective intervention, since transaction costs bar bargaining; and enclosure is itself costly, so some externalities are rightly left unpriced, too minor to warrant the machinery of ownership (Demsetz). The claim is that the priced/unpriced boundary is a movable legal-economic artifact, drawn where enclosure pays — not a natural fact.

With this the second of the failures advances the family's argument a decisive step. The asymmetry showed that the price cannot convey what one side hides — that its competence as a signal is conditional on shared knowledge. The externality shows something adjacent and as deep: that the price cannot count what no one owns — that its competence as an accounting is conditional on complete property. In each, a celebrated power of the price holds only under a condition the textbook leaves unspoken: the signal informs only when knowledge is shared, the ledger totals only when the world is owned. And in each, the failure is not rare but pervasive, for knowledge is everywhere unequal and the world is everywhere incompletely owned — the air, the sky, the oceans, the quiet, the climate, the vast commons of things no one has found it worth or possible to enclose. The price keeps a perfect ledger of the owned and is blind to all the rest; and since the rest is enormous, the price's account of what things cost is, across great reaches of the world, radically incomplete — complete only for that portion of the world we have carved into property, which is far from the whole.7

7. The family's theme advanced: the asymmetry showed the price's competence as a signal is conditional on shared knowledge; the externality shows its competence as an accounting is conditional on complete property. Both powers hold only under unstated conditions, and both fail pervasively — knowledge is everywhere unequal; the world everywhere incompletely owned. The price perfectly accounts for the owned and is blind to the rest.

So the externality, rightly seen, is not a leak in the price but the shadow of property — the measure of how much of the world lies outside the boundary we have drawn around the owned. The price was offered to us as the full reckoning of what a thing costs; it is, in truth, the reckoning of what a thing costs those who hold the rights to its costs, and silent about all it visits on the unowning and the unowned. Where that silence is small, we may ignore it; where it is large — the fouled river, the warming sky — we must choose whether to break it, by drawing the boundary of property outward to enclose the harm, or by taxing or ruling where no bargain can reach. And that choice returns us to the family's final and largest case, the one this volume has circled and the next will face directly: the resource owned by everyone and so by no one — the common pasture, the open sea, the atmosphere itself — where the externality is not one neighbor's smoke upon another's wash, but every user's burden upon every other, and the boundary of property, which here would have to be drawn around a thing the whole world shares, is hardest of all to draw. The asymmetry was the price that cannot convey what is hidden; the externality, the price that cannot count what is unowned; and the commons, which comes next, the price that cannot defend what is shared.8

8. The close looks ahead: the externality is the shadow of property — the measure of the world outside the boundary of the owned. The next failure, The Commons, treats the hardest case: a rivalrous resource owned by all and none (pasture, ocean, atmosphere), where externalities are mutual among many users and property is hardest to define. The triad — the price that cannot convey what is hidden (asymmetry), cannot count what is unowned (externality), cannot defend what is shared (commons).