Public Goods, Commons, and Institutional Choice

Part A treated externalities as effects that escape an agreed price because the relevant rights are missing, vague, or costly to enforce. Clear rights sometimes permit bargaining; when many parties are involved, taxes or tradable permits can make users face a cost they otherwise escape. Part B turns to two harder cases: benefits that many people can use at once, and resources that anyone can enter but each user can deplete.

The labels matter because the problems point in opposite directions. A public good may be undersupplied because non-payers cannot easily be excluded. A commons may be overused because no owner can protect its future value. Neither label selects a remedy automatically. The institutional question is how to create enough control, payment, and accountability to align choices with the costs they impose.

A Public Good Is One Whose Use by One Person Does Not Reduce Another’s

We have been talking about goods that one person consumes: if I eat an apple, you cannot. Those are private goods. A public good is different. Once it has been produced, one person’s use of it does not reduce the amount or worth available to anyone else. My getting more of it does not leave you with less. A mathematical theorem, a broadcast program, a lighthouse beam, some forms of national defense: my having the benefit leaves yours untouched. Economists call this nonrivalry in consumption, and it is the defining feature. A second feature often travels with it, nonexcludability, the difficulty of keeping non-payers out, but nonrivalry is the heart of the definition.

Two confusions are worth heading off, since exam questions love both. The first: nonrivalry is a fact about consumption, not about production. Someone might claim we can produce more of a public good without giving up other goods, but that is false. Producing the broadcast, writing the theorem, building the defense, all of it consumes scarce resources like anything else. What is costless is the extra use of the good once it exists, not its creation. The second confusion is to think anything shared is a public good. A theater performance is shared, but it is not a public good, since seats are limited and every spectator who gets in keeps someone else out. Goods with limited capacity are rival, and rivalry, not the mere fact of being enjoyed together, separates a public good from a private or congestible one.

This difference also changes how we add up what a good is worth. For a private good, market demand is the horizontal sum of individual demands: at a common price you add the quantities each buyer wants, since only one person can consume each unit. A public good flips the axis. Because everyone uses the same single unit at once, you add the values each user places on a given quantity, a vertical sum at a common quantity. If three viewers value one more program on a broadcast at $5, $3, and $2, its marginal value to society is their sum, $10, and the program is worth producing whenever it costs less than that. A private producer who can collect from only some of those viewers sees only part of the $10, so he underprovides. It is also just where honesty breaks down, since no one has to reveal what a shared good is truly worth to him.

The Free-Rider Problem Makes Public Goods Hard to Pay For, and There Are Three Standard Fixes

If a good is nonrival and hard to exclude people from, a problem appears for anyone who would supply it. Why pay for something you can enjoy whether or not you chip in? This is the free-rider problem: since non-payers cannot easily be shut out, the reward for creating and maintaining a public good is hard to collect, so too little tends to get made. Three remedies recur, all variations on one theme, finding a way to make the beneficiaries pay.

The first is government provision financed by taxes. A government can do what a private supplier cannot: use force to collect payment and punish free-riding, jailing or fining the person who refuses to pay. This is how we fund mosquito control, flood control, streets, and police patrols, which carry strong public-good features. When the government charges a fee for access, people sometimes protest the very idea of an admission price, but the price serves a purpose beyond raising money. It rations use, and rationing can keep a shared good from being loved to death, which brings us to the commons shortly.

The second fix is the private club: a firm in which the investors and the customers are the same people, who band together to provide a public good for themselves and pay for building and running it. A members-only golf course, a yacht club, or a fraternal hall all work this way. What makes a club possible is excludability. Since members can keep non-members out, they can be sure those who enjoy the good are the ones who paid for it, which defeats the free-rider problem from the inside. How a club hands out membership matters here. A closed group that admits new members only by sale, the way a country club does, gives each member a stake he can cash out, so members tend to husband the place; an open group whose membership cannot be sold weakens that stewardship, since no one captures the value of caring for what he will simply leave behind. Shared ownership of this open, nonsalable kind is exactly why your college, where you cannot sell your place in the student body, runs short on the control and alienability that make a private owner careful. Whole nations have a faintly club-like quality, part of why residents so often resent newcomers who arrive without having paid in.

The third fix is the tie-in, the cleverest. Some public goods cannot exclude non-payers at all yet get supplied privately anyway, sometimes precisely because the free-riders are welcome. Broadcast television and radio are the classic case. You pay nothing to watch, and nobody is shut out, but the program is not really free: the price is your attention during the advertisements, time that has other uses. The broadcaster cannot force you to watch the ads, but when you tune in for the program, the ads ride along as the price of admission. Newspapers and magazines, priced far below what they cost to make, are funded the same way. One useful corollary of such tied and charitable financing: a gift earmarked for something the recipient would have bought anyway frees up his own funds for other uses, since a dollar is a dollar wherever it comes from. We will leave the full who-gains-what arithmetic of earmarked gifts for class; the principle is what matters here.

The Tragedy of the Commons: Unowned Resources Get Used Up Too Soon

The flip side of the public good is the common-pool resource, where the absence of property rights bites hardest. A common-pool resource is open to all but used up in the using: a fishery, a public pasture, a forest, the apples on that park tree. Picture the tree again. Why do the apples get picked before they ripen? Not because anyone prefers sour fruit, but because no one owns the tree. If you wait for an apple to ripen, someone else picks it green first, so the rational move for each person is to grab it now, and the result is a resource harvested too soon and too hard. The same logic drove the American bison to the edge of extinction and threatens whales and seals: with no owner to husband the stock, each taker races the others to the kill. An owner faces the opposite incentive, since the future value of the herd or orchard is captured in what he could sell it for, so he has every reason to preserve it and harvest at the right time and rate.

Stock a lake with fish nobody owns, and you get the fishery version. The fish caught run younger and smaller than in a privately owned lake, for the same reason the park apples come down green: the only way to capture a fish’s value is to catch it before someone else does. Worse, the open lake draws in too much effort. Each fisher judges the worth of his own catch, never the total drain on the stock, so people pour more boats, gear, and hours into catching fish than the extra fish are worth to society. That double waste, fish taken too young and resources squandered racing to take them, traces straight back to a missing, unenforced property right.

This is also why “public good” and “commons” shade into each other once a crowd shows up. Let everyone in for free and the park, the road, or the beach gets congested, and now my use really does subtract from yours. Yesterday’s public good becomes today’s congested good, and the response is the same tool we keep meeting: control entry, or charge a price that rations access before the good is destroyed.

Who Bears the Cost Is a Political Question, Not Just an Economic One

I want to close by widening the lens from allocation to politics, since every remedy we have discussed lands its costs on some identifiable group, and the one a society actually adopts depends on who can capture the gains and who can be made to bear the costs. A ban, a tax, a permit market, public provision: none is free, and choosing among them is as much a political contest as an economic calculation.

The decision-maker’s own incentives steer the outcome. A private owner who can pocket the proceeds, the residual claimant on what he controls, has every reason to price a resource to clear and redeploy it when it would be worth more elsewhere; he eats the consequences of getting it wrong. A salaried administrator who cannot personally bank the gain answers to other rewards, prestige, popularity, the approval of donors, and so he may keep a public golf course underpriced long after a private owner would have sold the land, or hand out admissions and licenses below clearing to serve goals unrelated to revenue. The same divide explains why a license awarded “to the most deserving” rather than sold to the highest bidder draws lawyers and lobbyists who burn real resources competing for it, sometimes spending nearly as much as the license is worth.

Notice what stands behind that administrator. In a nonprofit or a government agency, no one owns the residual: no one can sell the assets or pocket the gains, so its operators have weaker reason to heed the marketable value of what they do. And where a private owner has one sharp target, profit, such a body is handed an ambiguous one, to “maximize public welfare,” with no crisp test of whether it is doing its job. Less able to price to clear, it is more prone to chronic shortages or surpluses and to nonprice rationing among buyers. The Postal Service is the clean illustration. It is built to pay its own way: by its own account it “generally receives no tax dollars for operating expenses,” and Congress shields its carriage of letters with a monopoly the GAO valued near $5.45 billion in fiscal 2015. Yet no one can claim the residual, and no bankruptcy or takeover forces a reckoning. It has lost money in every fiscal year but one since 2007, about $118 billion in cumulative losses, including $9.5 billion in fiscal 2024, and the GAO has kept its finances on the federal High-Risk List since 2009. Most of that loss traces to legislated pension and benefit accounting, not everyday waste; the structural point is that where no owner gains from closing the gap between cost and value, nothing forces it closed.

The contest also tilts toward concentrated interests. The cost of a remedy is often spread thinly across millions of taxpayers while its benefits pile up on a few, or the reverse, and the side whose stake is concentrated has far more reason to organize, lobby, and vote than the side whose stake is diffuse. So the remedy that wins is frequently not the one that does the most good overall but the one whose winners were best positioned to push it through.

There is a rhetorical hazard here too. Because so many goods carry some public-good character, “this is a public good” is an argument available to almost any group that wants a subsidy. It is genuinely not known how much of the debate over what government should do reflects a real concern that shared goods be valued properly, and how much merely dresses up a bid for subsidies to one’s own interest. The label alone cannot tell you which. And public-good features settle nothing by themselves, since plenty of goods that have them are supplied privately anyway: broadcast television, and ideas, which patents and copyrights fence off well enough to sell.

The same caution applies to redistribution. A program described as helping the poor need not transfer resources from richer people to poorer ones once all its effects are counted. Below-cost tuition at a state university subsidizes students whose current income is low but whose expected lifetime income may be high, including many people reading this page. Tariffs can raise the prices poorer households pay while protecting higher-income workers and owners in the favored industry. A government can even create or operate a monopoly, such as a state liquor store, partly to collect its monopoly return. The relevant question is not the program’s label but who ultimately receives the benefit and who bears the full cost.

Property systems also differ in how they distribute profits and losses. Under private property, a resource’s owner bears its rise or fall in value and can buy or sell holdings to choose which mix of risks he wants to carry. Under socialism, individuals cannot assemble that portfolio for themselves; gains and losses reach them through taxes, access to government resources, and the powers attached to political office. The risks do not disappear. The institution changes who bears them and how much discretion each person has to trade one exposure for another.

Watch all of this play out in one ordinary fight. A town owns an airport, and a developer holds a large parcel nearby. The town fears that families who move into new homes will complain about the noise and force the airport to cut back its operations, so it passes a zoning rule forbidding houses on the parcel. Notice first that any rule of this kind is two-sided. Whenever the law clarifies one party’s right, it necessarily curtails another’s: if a city says your neighbor’s building may not cast a shadow on your land at midday, it has strengthened your right to sunlight and, in the same stroke, narrowed his right to build as he pleases. There is no clarification that adds to one side without subtracting from the other. So whose rights does the airport rule curtail? If the developer bought the land when home-building was already allowed, the new rule takes a right he had paid for. But if there was no such rule when he bought, the ordinance is not really a taking; it defines and assigns, for the first time, a right that had been left vague, which is exactly why a careful buyer asks what the land may be used for before he pays, rather than after.

And zoning is not the only fix. A lighter one leaves the rights where they are and writes the conflict into a contract: require that any sale of the land to a home-builder disclose the airport next door. Buyers who know about the noise will pay less, the lower price reflects the nuisance, and the families who do move in have no standing to complain about a cost they were told of and accepted. The damage gets priced rather than prohibited, which is the Coasean move in another guise. Which fix a town actually picks, though, turns on the politics. A taxpayer who lives nowhere near the airport tends to vote for the homes, since more houses mean more residents paying property taxes for schools and services he uses, and his stake, like the developer’s, is concentrated enough to organize around, while the scattered would-be neighbors’ is not. Diagnosing an externality as a missing or unassigned property right tells you the economics; asking who bears the cost of the cure, and who has the motive and means to choose it, tells you the politics.

The economic diagnosis narrows the choices without pretending to make a value judgment for us. Ask who can control the resource, who can be excluded, whose use subtracts from another’s, and who captures the future value of restraint. Then ask the political question: who has the incentive and ability to choose the rule? Those two layers—resource characteristics and institutional incentives—are the durable lesson of this topic.

T9 will take the residual-claimant mechanism used here and develop it into a full theory of firms, monitoring, and organizational governance.