Microeconomics
Public Goods
Non-excludable, non-rival — markets underprovide because of free riders
Public goods have two key properties: (1) Non-excludable — can't prevent non-payers from using. (2) Non-rival — one person's use doesn't reduce availability for others. Examples: national defense, clean air, lighthouses, public radio, fundamental research. Markets fail to provide adequate amount because of free-rider problem — incentive to use without paying. Solutions: government provision (taxes), assurance contracts (Kickstarter-style), club goods, charity. Different from: private goods (excludable, rival), common-pool resources (rival, non-excludable), club goods (non-rival, excludable).
- Two key propertiesNon-excludable, non-rival
- Free rider problemIncentive to use without paying
- Market failureMarkets underprovide
- ExamplesNational defense, clean air, lighthouses, basic research
- SolutionsGovernment provision, assurance contracts, club goods
- FoundationSamuelson 1954, mathematical analysis
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Why public goods matter
- Government role. Why government exists.
- Public economics. Foundation.
- Environmental policy. Clean air, climate.
- Research funding. Why governments fund.
- Tax policy. Justifying taxation.
- Crowdfunding. Modern alternative mechanisms.
- Education. Foundational economics.
Common misconceptions
- Just government goods. Definition based on properties.
- Always under-provided. Some private provision works.
- Pure public goods common. Most are mixed.
- Same as common-pool. Different (rival vs non-rival).
- Government always best provider. Trade-offs in different mechanisms.
- Solves all market failures. Specific to non-excludable, non-rival.
Frequently asked questions
What's a public good?
Two properties. (1) Non-excludable: can't prevent non-payers from using. National defense protects all citizens; can't exclude tax avoiders. (2) Non-rival: one person's use doesn't reduce availability. Lighthouse benefits all ships passing. Both: must hold. Different from: private goods (excludable, rival — like food), club goods (non-rival but excludable — Netflix), common-pool (rival, non-excludable — fish).
Why do markets fail?
Free rider problem. People can use without paying. So: rational to wait for others to pay. Everyone reasons same way. Result: under-provision. Markets work when can charge and exclude. Public goods: neither. Even if value greater than cost, voluntary funding often inadequate. Government often steps in.
What about national defense?
Classic public good. Military protects all citizens (non-excludable). Protecting one doesn't reduce protection for another (non-rival). If voluntary funding: free-rider problem; under-provision. Solution: tax-funded; government provides. Most countries: national defense as government function. Demonstrates: some essential goods need collective action.
What about basic research?
Public good qualities. Scientific knowledge: non-excludable (once published, anyone can use). Non-rival (many can apply same insight). Markets underfund: hard to capture full value. Solutions: government funding (NSF, NIH), university research, foundations. Patent system: makes some research excludable (creates monopoly to fund) but trade-off with deadweight loss.
What's an assurance contract?
Funding mechanism. Promises: I'll contribute if enough others do. Threshold reached: all contribute. Below threshold: nothing happens. Solves free-rider partly. Modern: Kickstarter, crowdfunding. Limited applicability: works for some public goods, not all (national defense too big). Useful: smaller-scale public goods.
What about club goods?
Non-rival but excludable. Examples: Netflix subscriptions, private parks, gated communities. One can use without reducing others' use; but excluded if not paying. Markets can provide: charge subscribers; cover costs. Different from public goods (truly non-excludable). Many "public" services are actually club goods.
How are public goods funded?
Government provision: most common. Tax revenue; provided to all. Examples: roads, police, fire, schools, parks. Sometimes: government funds private provision (charter schools, defense contractors). Voluntary: charity, foundations, crowdfunding. Public-private partnerships. Each method: trade-offs in efficiency, fairness, accountability.