Chapter 12 — Public Goods and Common Resources

The Free Rider and the Tragedy of the Commons

Chapter 11 showed that externalities cause markets to produce the wrong quantity of a good — too much when there are negative externalities, too little when there are positive. This chapter introduces a related but distinct problem: some goods have properties that make markets unable to provide them efficiently at all.

The distinction comes from two features that every good either has or doesn't have: rivalry and excludability. Whether a good is rival or non-rival, and whether it is excludable or non-excludable, determines which of four categories it belongs to — and which of four very different economic problems it faces.

The chapter is built around the Millbrook downtown parking garage proposal — a local dispute that brings all four categories to life. By the end, you should be able to classify any good into the 2×2 matrix, identify the economic problem each category faces, and evaluate the main solutions.

12.1 The two dimensions: rivalry and excludability

Rival good: a good is rival if one person's use of it reduces the amount available for others. A slice of pizza is rival: if I eat it, you can't. A parking space is rival: if my car is in it, yours can't be.

Non-rival good: a good is non-rival if one person's use does not reduce the amount available for others. National defense is non-rival: my being protected by the military does not reduce your protection. A radio broadcast is non-rival: my listening doesn't prevent you from listening.

Excludable good: a good is excludable if it is feasible to prevent non-paying users from enjoying it. A movie ticket is excludable: the theater can refuse entry to non-payers. A cable TV channel is excludable: the company can scramble the signal.

Non-excludable good: a good is non-excludable if it is not feasible to prevent non-paying users from enjoying it. Clean air is non-excludable: you can't charge people for breathing. A lighthouse is (traditionally) non-excludable: any ship can see it.

These two dimensions combine into a 2×2 matrix — the most useful classification scheme in public economics.

                     EXCLUDABLE              NON-EXCLUDABLE

   RIVAL            PRIVATE GOODS           COMMON-POOL RESOURCES
                    (food, clothing,         (ocean fish, groundwater,
                     housing, most goods)     congested roads, clean air)

   NON-RIVAL        CLUB GOODS              PUBLIC GOODS
                    (cable TV, gyms,         (national defense, streetlights,
                     streaming services,      lighthouses, public parks,
                     toll roads)              basic research)

Figure 12.1 — The four categories of goods. Each category faces a different economic problem. Private goods work well in markets. Club goods work in markets with some mechanism for exclusion. Common-pool resources are prone to overuse (the tragedy of the commons). Public goods are prone to under-provision (the free-rider problem).

Let's walk through each.

12.2 Private goods: the easy case

Private goods are both rival and excludable. Most of what you buy is a private good: food, clothes, a haircut, a car, a laptop. Markets handle private goods well because:

1. Excludability lets sellers charge a price (non-payers don't get the good).
2. Rivalry means the good is scarce and has a meaningful opportunity cost.
3. The standard supply-and-demand framework applies directly.

Chapter 5's supply-and-demand model was built for private goods. Everything we've done since Chapter 5 — elasticity, surplus, taxes, trade — applies cleanly to private goods. No market failure here (assuming the other conditions from Chapter 8 hold: no externalities, good information, competition).

12.3 Public goods: the free-rider problem

Public goods are both non-rival and non-excludable. They are the polar opposite of private goods, and they are the category where markets fail most completely.

Examples: - National defense. Once a country has a military, every citizen is protected. My being protected doesn't reduce your protection (non-rival). And there is no way to protect some citizens but not others (non-excludable). - A lighthouse. Once lit, every ship at sea can see it. One ship seeing it doesn't reduce the light (non-rival). And you can't charge individual ships for the light — they can all see it regardless (non-excludable). (This is the traditional framing; modern lighthouses are sometimes excludable via electronic navigation aids.) - Basic scientific research. Once a scientific discovery is published, anyone can use it. My using Newton's laws doesn't prevent you from using them (non-rival). And you can't prevent someone from reading a published paper (non-excludable). - Clean air. We all breathe the same air. One person breathing doesn't reduce the air available to others (mostly non-rival — though polluted air is a common-pool problem). And you can't charge people for breathing clean air (non-excludable). - Street lighting. The light illuminates everyone on the block. One person's illumination doesn't reduce another's (non-rival). And you can't charge individual pedestrians for the light (non-excludable).

Why markets fail for public goods

The problem is free-riding. Because the good is non-excludable, I can enjoy it whether or not I pay. If national defense exists, I am protected even if I contribute nothing. If the lighthouse is lit, I can navigate even if I didn't pay for the light. If the park is maintained, I can enjoy it even if I didn't pay taxes.

If I can get the good for free, why would I pay?

The free-rider problem: when individuals can enjoy a good without paying for it, the private market provides too little of the good (or none at all), because each potential buyer has an incentive to "free ride" on others' contributions.

If everyone free-rides, no one pays, and the good isn't produced. Even if most people would benefit from the good and would willingly contribute to its provision if they could be sure everyone else would too, the incentive to free-ride undermines the system. This is a collective action problem — a situation where individual incentives and group interests diverge.

The standard solution: government provision

The traditional solution to public goods is government provision, funded by taxes. The government provides national defense, builds lighthouses, funds basic research, maintains streetlights, and runs public parks. Citizens pay through taxes — mandatory, non-voluntary payments that solve the free-rider problem by making everyone contribute.

This is why governments exist, in the economic view: to provide goods that markets cannot. The "minimal state" — the state that does nothing except enforce property rights and contracts — is a theoretical construct that ignores the public goods problem. A real economy needs a mechanism for providing public goods, and that mechanism is almost always the government.

How much should the government provide? The optimal quantity of a public good is where the sum of everyone's marginal benefits equals the marginal cost of provision. (For a private good, it's where the individual's marginal benefit equals the marginal cost. For a public good, because the good is non-rival, every person benefits simultaneously, so you sum the benefits.) In practice, governments estimate this through cost-benefit analysis, though the analysis is inevitably imperfect because people have incentives to overstate their benefits (to get more of the good) or understate them (to pay less tax).

12.4 Common-pool resources: the tragedy of the commons

Common-pool resources are rival but non-excludable. They are the category that produces the tragedy of the commons.

Examples: - Ocean fish. Fish are rival (if I catch one, you can't). But they are non-excludable in international waters (no one owns the ocean; anyone can fish). - Groundwater. Water in an aquifer is rival (if I pump it, there's less for you). But it's non-excludable (anyone whose land is over the aquifer can pump). - Congested roads. Road space is rival during rush hour (if my car is in a lane, yours can't be). But non-excludable (any car can drive on a public road). - A shared office refrigerator. The food in it is rival (if I eat your yogurt, you can't). But non-excludable (anyone in the office can open the fridge).

The tragedy

The tragedy of the commons is the result of each individual user having an incentive to use more of the resource than is socially optimal.

The classic formulation (Garrett Hardin, 1968): imagine a pasture shared by several herders. Each herder grazes cattle on the commons. The benefit of adding one more cow to the pasture is captured entirely by the herder (the profit from one more cow). The cost of adding one more cow — the reduced grazing for all other cattle — is shared among all herders. Because the individual benefit exceeds the individual cost (even though the social cost exceeds the social benefit), each herder adds more cattle. The commons is overgrazed. If each herder acted in perfect self-interest, the pasture is destroyed.

The tragedy is a special case of a negative externality (Chapter 11), but it has a distinct structure: the resource is shared, open-access, and depletable. The market doesn't assign a price to the resource (because no one owns it), so the resource gets overused.

Real-world tragedies: - Overfishing. Atlantic cod stocks collapsed in the 1990s. Grand Banks cod, once one of the world's great fisheries, was fished to commercial extinction. The classic tragedy: each boat had an individual incentive to catch more; the aggregate result was collapse. - Aquifer depletion. The Ogallala Aquifer under the U.S. Great Plains is being pumped faster than it recharges. Individual farmers have an incentive to pump as much as they need; the aggregate result is declining water tables. - Traffic congestion. Each driver choosing to drive during rush hour captures the full benefit of their trip but bears only a small share of the congestion they impose on everyone else.

Three traditional solutions

1. Privatization. Assign property rights. If someone owns the resource, they have an incentive to manage it sustainably (because depleting it destroys their asset). This works for land, forests, and some fisheries (tradable fishing quotas are a form of privatization). It doesn't work for the atmosphere or the open ocean.

2. Government regulation. Limit access (fishing quotas, pumping limits, road tolls). The government decides how much use is sustainable and enforces the limit. This works when monitoring is feasible and political will exists. It doesn't work when enforcement is impossible or the government is captured by users.

3. Community governance (Ostrom). Elinor Ostrom (Nobel Prize 2009) demonstrated that communities can sometimes manage commons without either privatization or government regulation. Her work, based on field studies of commons around the world — irrigation systems in Nepal, lobster fisheries in Maine, pastures in Switzerland, forests in Japan — showed that communities develop institutions, rules, and norms that prevent overuse.

12.5 Elinor Ostrom and the managed commons

Ostrom's contribution was to challenge the simple "tragedy → privatize or regulate" framing. She showed that real human communities had been managing commons for centuries — often successfully — without either selling off the resource or handing it to the government. The solution was community governance: a set of rules, developed and enforced by the community of resource users themselves.

Ostrom identified eight "design principles" that characterized successful commons governance:

1. Clearly defined boundaries — who can use the resource is known and enforced
2. Rules matched to local conditions — the rules fit the specific resource and the specific community
3. Collective-choice arrangements — most of those affected by the rules can participate in making them
4. Monitoring — there is a system for observing whether users comply with the rules
5. Graduated sanctions — rule-violators face escalating penalties, starting mild
6. Conflict-resolution mechanisms — there are local, inexpensive ways to resolve disputes
7. Recognized right to organize — external authorities (the government) don't undermine the community's ability to manage itself
8. Nested enterprises — for large resources, governance is layered (local rules within broader frameworks)

These principles are not a formula — they are patterns observed in successful commons governance around the world. Not every commons can be managed this way (Ostrom was careful to say so). But many can, and the "tragedy of the commons" is not the inevitable outcome the simple model suggests.

The Millbrook parking example

The Walden County Council has been debating whether to build a downtown parking garage near the Millbrook State University campus. The current situation: downtown Millbrook has about 500 metered street parking spaces and several small private lots. During weekday business hours and Friday/Saturday evenings, parking is scarce. Students, shoppers, restaurant-goers, and MSU employees all compete for spaces. The result is congestion (driving around looking for parking), illegal parking, and frustration.

Is downtown parking a public good? A private good? A common-pool resource?

Apply the matrix: - Rival? Yes — if my car is in the space, yours can't be. Parking is rival. - Excludable? It depends on the design. Street parking with meters is partially excludable (you have to pay, but enforcement is imperfect). A parking garage with a gate is fully excludable (you pay to enter). An unmetered lot is non-excludable (anyone can park).

So downtown parking is somewhere between a private good and a common-pool resource, depending on how it's managed. If the parking is metered and enforced, it's closer to a private good. If it's unmetered and first-come-first-served, it's a common-pool resource — and the tragedy of the commons applies (too many people drive downtown expecting to park, causing congestion and wasted time searching).

The proposed parking garage would make the resource more excludable (gated entry, paid parking), which would move it from the common-pool quadrant toward the private/club quadrant. This is a design choice — and it has economic consequences.

If the garage charges market-rate parking ($3/hour), it would allocate spaces efficiently (people who value the space most pay for it). If it charges too little (free parking), it would face the tragedy of the commons: too many drivers, too few spaces, long waits. If it charges too much ($10/hour), the garage would be half-empty and the investment would not be justified.

The council is debating all of these options. The economics is straightforward — price the parking to reflect the scarcity. The politics is harder — free parking is popular, and charging for it feels like taxing the public for using public infrastructure. This is the same tension that shows up in every discussion of pricing a good that people have come to expect for free.

12.6 Club goods: the intermediate case

Club goods are non-rival (up to a point — congestion can make them rival) and excludable. They are the category that private markets handle reasonably well through membership or subscription models.

Examples: - Streaming services (Netflix, Spotify). My watching a movie doesn't prevent you from watching (non-rival). But you need a subscription to access it (excludable). - Gym memberships. My using the treadmill doesn't prevent you from using another (non-rival, up to capacity). But you need a membership to enter (excludable). - Toll roads. My driving on the toll road doesn't prevent you from driving (non-rival, until congestion). But you need to pay the toll (excludable). - Cable TV. Same logic. - Private parks and beaches. Same logic.

Club goods work in markets because excludability lets the provider charge. The free-rider problem doesn't apply (non-payers are excluded). The non-rivalry means the marginal cost of adding one more user is approximately zero, which creates a tension: the efficient price for an additional user is zero (since their use doesn't reduce anyone else's benefit), but the provider needs to charge a positive price to cover costs. This is the tension between "efficient pricing" and "cost recovery" that shows up in digital goods, streaming, and many subscription services.

12.7 What this chapter taught

You should now be able to:

1. Classify any good into the 2×2 matrix (rival/non-rival × excludable/non-excludable)
2. Identify the free-rider problem for public goods and explain why markets underprovide them
3. Identify the tragedy of the commons for common-pool resources and explain why they are overused
4. Evaluate three traditional solutions (privatization, regulation, community governance)
5. Apply Ostrom's design principles to evaluate whether a specific commons can be managed by its community
6. Analyze the Millbrook parking garage as a case where the category of the good depends on design choices

In Chapter 13, we'll turn to the economics of inequality — a topic where the efficiency-equity tradeoff from Chapter 8 becomes the central question.

Key terms recap: rival — one person's use reduces availability for others non-rival — one person's use doesn't reduce availability for others excludable — non-payers can be prevented from using the good non-excludable — non-payers cannot be prevented private good — rival + excludable (markets work well) public good — non-rival + non-excludable (free-rider problem → government provision) common-pool resource — rival + non-excludable (tragedy of the commons → regulation, privatization, or community governance) club good — non-rival + excludable (subscription/membership models) free rider — someone who enjoys a good without paying for it tragedy of the commons — overuse of a shared resource because individual incentives don't account for the social cost Ostrom's design principles — eight conditions for successful community-managed commons

Themes touched: Markets power+imperfect, Tradeoffs, Disagreement (about Ostrom vs. privatization vs. regulation), Affects daily life (parking, roads, public parks, fish, water).