Public goods

What you'll learn

• How to distinguish private goods, public goods and quasi-public goods.
• The key characteristics: non-excludability, non-rivalry, non-rejectability and zero marginal cost.
• Why the free rider problem can cause missing markets or under-provision.
• How to evaluate whether public goods should be provided by the state, the market, or a mixture of both.

Start point: why goods need classifying

In a market economy, goods are usually allocated through prices. If you want a good, you pay for it; if producers can earn profit, they supply it.

But some goods do not fit neatly into this system. The problem is not just that they are “important” or “nice to have”. The issue is whether firms can charge users and whether one person’s consumption prevents others from consuming the same good.

This is why economists classify goods using two key questions:

• Can non-payers be excluded?
• Does one person’s use reduce the amount available for others?

Private goods

Excludable means a supplier can prevent people from consuming the good unless they pay. For example, a shop can stop you taking a sandwich without paying.

Rival means one person’s consumption reduces the amount available for others. If you eat the sandwich, nobody else can eat that exact same sandwich.

Most ordinary market goods are private goods: food, clothes, phones, train tickets with limited seats, and haircuts.

Public goods

A pure public good is difficult for private firms to provide profitably because users can benefit without paying, and one extra user does not normally reduce the benefit to others.

Classic examples include:

• national defence
• flood defence systems
• street lighting
• lighthouse signals
• basic public safety information, such as emergency warnings

The classification matrix below shows how public goods differ from private goods and some “in-between” cases.

Quasi-public goods

Many real-world goods are not perfectly private or perfectly public. For example, a road may be non-rival when empty, because one extra car does not affect other drivers. But at rush hour, it becomes rival because congestion reduces the benefit for everyone.

Examples of quasi-public goods include:

• roads and bridges
• public parks
• beaches
• policing in specific areas
• public broadcasting
• museums and libraries

The characteristics of a public good

Non-excludability

National defence is the classic example. If the UK is defended from attack, it is extremely difficult to exclude one household from that protection because they did not pay directly.

This creates a problem for private firms. If a firm cannot restrict access to paying customers, it may struggle to earn revenue.

Non-rivalry / non-diminishability

If one more person benefits from a lighthouse signal or a streetlight, the signal or light is still available to others. The good is not “used up” by an additional consumer.

This matters because efficient pricing becomes tricky. If the cost of one extra user is zero, charging a positive price may exclude people even though society could let them consume the good at no extra resource cost.

Zero marginal cost

This does not mean the good is free to create. A flood barrier may cost millions of pounds to build. The point is that once it exists, protecting one extra household in the area may add no extra cost.

So public goods often have:

• high fixed costs
• very low or zero marginal costs
• difficulty charging individual users

Non-rejectability

If national defence or flood protection covers your area, you receive the benefit whether or not you personally wanted to buy it. You cannot realistically reject the protection in the way you could refuse to buy a private good.

This strengthens the case for collective decision-making, usually through government, because individual market choices do not reveal demand accurately.

The free rider problem

If everyone waits for someone else to pay, the good may not be provided at all, even if society would benefit from it. This is a form of market failure, meaning the free market leads to an inefficient allocation of resources.

For public goods, the free rider problem is especially serious because non-excludability makes it hard to force individual payment through normal market transactions.

Why markets may fail to provide public goods

Private firms usually need revenue to cover costs. For public goods, this is difficult because:

• non-payers cannot easily be excluded
• consumers may hide their true willingness to pay
• the good may have high fixed costs
• the marginal cost of extra users may be zero
• charging a price can be inefficient if it excludes people unnecessarily

In a normal market, demand reflects willingness and ability to pay. With public goods, demand is often hidden because people have an incentive to free ride. This can create a missing market, where no private market develops even though the good would improve social welfare.

Provision of public goods

The main policy question is: who should provide public goods, and how should they be paid for?

Government provision

Governments can provide public goods directly and finance them through taxation. For example, UK national defence is funded through general taxation rather than individual user charges.

This can solve the free rider problem because taxation is compulsory. It also allows decisions to be based on estimated social benefits, not just private profitability.

However, government provision has drawbacks:

• taxes have an opportunity cost because money could be used elsewhere
• governments may misjudge demand or costs
• public projects can suffer from inefficiency or delays
• political incentives may distort spending decisions

Private provision

Some public or quasi-public goods can be provided privately if technology makes exclusion possible. For example, encrypted broadcasting, toll roads, subscriptions and paywalls can turn some non-excludable goods into excludable ones.

This can reduce the burden on taxpayers and introduce competition. But it may also exclude low-income users, creating equity concerns, especially where the good has wider social benefits.

Voluntary provision and charities

Some goods are provided through donations, charities or community action. For example, local fundraising may support public defibrillators, parks or environmental projects.

This can work where communities are small and social pressure is strong. But it is less reliable for large-scale goods such as national defence or flood protection.

Evaluating the provision of public goods

A strong evaluation should avoid saying “the government should always provide public goods”. Instead, compare options.

For pure public goods such as national defence, state provision is usually the strongest solution. Non-excludability is extreme, the free rider problem is severe, and the benefits are national in scale.

For quasi-public goods, a mixed approach may be better. For example, roads can be funded through taxation, tolls, congestion charges, or public-private partnerships. The best choice depends on congestion, equity, administrative costs and environmental objectives.

Useful real-world application

Public goods are especially relevant to:

• national defence, including UK defence spending commitments
• flood protection, particularly as climate change raises flood risks
• street lighting and public safety, funded by local authorities under budget pressure
• clean air and climate stability, which have global public good characteristics
• public health information, such as vaccination campaigns and emergency alerts

Climate change is a powerful synoptic link. A stable climate is close to a global public good: countries benefit from emissions reduction whether or not they contribute. This creates an international free rider problem, making agreements such as COP summits difficult to enforce.

Bringing it together

Public goods matter because they show a limit of the price mechanism. Markets work well when firms can charge users and consumption is rival. But when goods are non-excludable and non-rival, individual incentives can conflict with social welfare.

The result may be under-provision, non-provision, or reliance on government intervention. Your evaluation should focus on whether intervention improves welfare after considering opportunity cost, information problems and incentives.