Why will a market never supply street lighting, and why does it under-supply healthcare?
Distinguish public goods from merit and demerit goods and explain why each is mis-provided by the market
A focused answer to the H2 Economics learning outcome on public and merit goods. The non-rival and non-excludable properties of public goods and the free-rider problem, and why merit goods are under-consumed and demerit goods over-consumed.
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What this dot point is asking
SEAB wants you to distinguish public goods (defined by non-rivalry and non-excludability) from merit and demerit goods (defined by a gap between private and social valuation), and to explain why each is mis-provided by the market. The central insight is that public goods are not provided at all, while merit goods are under-provided and demerit goods over-provided.
The answer
Public goods
These properties cause total market failure through the free-rider problem. Because consumers cannot be excluded, no one will pay voluntarily; each free-rides on the hope that others will pay. With no one willing to pay, a profit-seeking firm cannot cover its costs, so the market provides none of the good, even though society values it. This is why public goods are funded by the government through taxation.
Many real goods are quasi-public: they have the properties only partly (a road is non-rival until congested, and can be made excludable with tolls), so some private provision is possible.
Merit goods
Crucially, merit goods are rival and excludable, so the market does provide them, just too little. Two forces cause under-consumption: positive externalities (, as with education's spillovers) and information failure or short-sightedness, where consumers underestimate the future private benefit. Governments respond with subsidies, direct provision or, for the strongest cases, compulsion.
Demerit goods
Over-consumption arises from negative externalities () and information failure or present bias. Governments respond with taxes, regulation, advertising bans and information campaigns.
Examples in context
Example 1. National defence in Singapore. Defence is the textbook public good: it protects every resident regardless of whether they contribute, and one person's protection does not reduce another's. No market could sell it, so it is funded entirely through the national budget, with conscription supplying part of the labour, an example of the state stepping in where the free-rider problem makes private provision impossible.
Example 2. Subsidised healthcare and education. Singapore heavily subsidises education and co-funds healthcare through schemes that lower the price of consumption. These merit goods would be under-consumed if left to the market because individuals under-weigh long-term and external benefits, so subsidy and provision push consumption toward the social optimum.
Try this
Q1. State the two properties of a pure public good. [2 marks]
- Cue. Non-rival (one person's consumption does not reduce what is available to others) and non-excludable (no one can be prevented from consuming it once provided).
Q2. Explain the free-rider problem. [3 marks]
- Cue. Because a public good is non-excludable, each consumer waits for others to pay and free-rides on their payment; with no one willing to pay, no firm will provide it, so the market supplies none.
Q3. Explain why education is a merit good. [2 marks]
- Cue. It is provided by the market but under-consumed, because it has positive externalities and consumers under-value its long-term private benefit, so output is below the social optimum.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original10 marksExplain, using the properties of public goods, why the free market fails to provide them, and how this differs from the under-provision of merit goods.Show worked answer →
A 10 mark question rewards the two public-good properties, the free-rider problem, and a clear contrast with merit goods.
- Public-good properties
- A pure public good is non-rival (one person's consumption does not reduce what is available to others) and non-excludable (no one can be prevented from consuming it once provided).
- Why the market fails
- Non-excludability creates the free-rider problem: since people cannot be charged, each waits for others to pay, so no one pays and a profit-seeking firm will not supply it. The market provides zero, even though society values the good. Examples: national defence, street lighting.
- Contrast with merit goods
- A merit good (education, healthcare) is excludable and rival, so the market does provide it, but under-provides it relative to the social optimum because of positive externalities and because consumers under-value the long-term private benefit. The failure is partial, not total.
Markers reward the two properties, the free-rider explanation of total non-provision, and the contrast that merit goods are under-provided rather than not provided at all.
Original8 marksExplain why a demerit good is over-consumed in a free market, and why this represents a market failure.Show worked answer →
An 8 mark question rewards the demerit-good definition, the reasons for over-consumption, and the welfare argument.
- Demerit good
- A demerit good is one that is more harmful than consumers privately realise, such as tobacco or excessive sugar.
- Why over-consumed
- Two reasons: negative externalities (harm to others, such as second-hand smoke or healthcare costs) mean exceeds ; and information failure plus present bias mean consumers over-value the private benefit, so overstates true benefit. Both push consumption above the social optimum.
- Market failure
- Because consumption exceeds the level where , the extra units cost society more than they are worth, creating a welfare loss. The market over-allocates resources to the demerit good.
Markers reward the harmful-beyond-perception definition, the externality and information-failure reasons, and the welfare-loss conclusion.
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