Market failure and government intervention (SACE Stage 2 Economics)
“Explain the main types of market failure and evaluate government policies used to correct them.”
Market failure occurs when a free market allocates resources inefficiently, so society's welfare is not maximised. The main causes are externalities, public goods, asymmetric information and market power, and governments respond with taxes, subsidies, regulation and direct provision.
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What this dot point is asking
You need to identify the main types of market failure, explain why each one leads to an inefficient outcome, and evaluate the government policies used to correct them.
What market failure means
Markets usually allocate resources efficiently, but sometimes the price mechanism produces an outcome that is not in society's best interest. This is market failure: resources are over-allocated or under-allocated relative to the socially optimal level. The main types are externalities, public goods, asymmetric information and market power (covered in the market structures note).
Externalities
An externality is a cost or benefit imposed on a third party not involved in a transaction.
- Negative externalities (such as pollution from a factory) impose costs on others. The market over-produces because private producers ignore the external cost. The socially optimal output is lower than the market output.
- Positive externalities (such as vaccination or education) create benefits for others. The market under-produces because private buyers ignore the external benefit. The socially optimal output is higher than the market output.
An externality is a spillover cost or benefit from production or consumption that affects a third party who is not part of the transaction, and which is not reflected in the market price.
Suppose a coal-fired power station emits pollution costing society $30 per unit of electricity, but this cost is not in its price. The market over-produces. A government can impose a tax of $30 per unit, raising the firm's private cost to match the full social cost. This shifts the supply curve up (to the left), lifts the price, reduces quantity towards the socially optimal level, and raises revenue. The tax internalises the externality.
Public goods
Public goods, such as national defence, street lighting and lighthouses, have two features:
- Non-excludable - you cannot prevent people who do not pay from using them.
- Non-rival - one person's use does not reduce the amount available to others.
Because of the free-rider problem (people benefit without paying), private firms cannot profitably supply public goods, so the free market under-provides or fails to provide them at all. Governments typically fund them through taxation and provide them directly.
Asymmetric information
Markets work well when buyers and sellers are well informed. Asymmetric information occurs when one party knows more than the other - for example, a used-car seller knowing about hidden faults, or a borrower understanding their own risk better than a lender. This can lead to poor decisions and even market breakdown. Governments respond with disclosure rules, labelling laws and consumer protection regulation.
Government intervention: the policy toolkit
| Type of failure | Policy responses |
|---|---|
| Negative externality | Indirect taxes, pollution permits, regulation, bans |
| Positive externality | Subsidies, free provision, education campaigns |
| Public goods | Direct government provision funded by taxes |
| Asymmetric information | Disclosure laws, labelling, licensing, consumer law |
| Market power | Competition law (ACCC), price regulation |
Each policy has trade-offs. Taxes raise revenue and reduce harmful output but may be regressive and hard to set at the right level. Subsidies encourage beneficial goods but cost the budget and can be captured by producers. Regulation is direct but costly to monitor and enforce.
Intervention is not always an improvement. Government failure occurs when intervention produces a worse outcome than the market, for example through high administration costs, unintended consequences, poor information, or political pressure. Evaluating a policy means weighing the gain from correcting market failure against the risk of government failure.
Why this matters
Market failure is the economic justification for almost everything governments do in microeconomics, from carbon pricing to public health and consumer protection. In the Economic Project, contemporary issues such as climate policy, housing affordability or vaping regulation are usually framed as market failures, so this dot point gives you the analytical tools to investigate them.
A strong answer does not just identify a failure and recommend a tax or subsidy. It evaluates whether the proposed policy actually corrects the failure efficiently, considers its costs and side effects, and weighs the possibility of government failure. The test is whether intervention makes society better off overall, not merely whether the market is imperfect.
Exam-style questions
Questions in the style of SACE Board exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
2022 SACE Stage 2-style2 marksGovernments highlighted the social and private benefits of wearing medical-grade face masks, including better public-health outcomes and reduced risk to healthy individuals of infection. Explain why the wearing of medical-grade face masks is associated with positive consumption externalities.Show worked answer →
Two marks: define the positive consumption externality and identify who gains.
Spillover benefit to third parties. When an individual wears a face mask, the benefit is not confined to that person. Others nearby gain because the wearer is less likely to spread the virus, so there is a positive external benefit to people who are not part of the transaction.
MSB exceeds MPB. Because of these spillover benefits, the marginal social benefit (MSB) of mask wearing is greater than the marginal private benefit (MPB) to the individual buyer. This gap between social and private benefit is what defines a positive consumption externality, and it means the free market under-consumes masks relative to the socially optimal level.
2022 SACE Stage 2-style3 marksIn an attempt to increase the supply of medical-grade face masks, governments offered large subsidies to encourage firms in other industries to switch to producing the specialised fabric used in these masks. Analyse the effectiveness of this policy, referring to one intended and one unintended consequence of the subsidies.Show worked answer →
Three marks: explain how the subsidy works, then give one intended and one unintended consequence.
- How it works (1 mark)
- A subsidy lowers producers' costs, shifting the supply curve of the specialised fabric to the right. This increases the quantity supplied and lowers its price, which feeds through to greater supply of face masks - the intended correction of the shortage.
- Intended consequence (1 mark)
- More firms switch into producing the fabric, raising output of masks towards the socially optimal level and easing the shortage during the pandemic.
- Unintended consequence (1 mark)
- Drawbacks such as the opportunity cost of government funds (money diverted from other uses), firms leaving their original industries (creating shortages there), or producers becoming reliant on the subsidy and over-supplying once demand falls. A balanced "analyse" answer weighs the gain against at least one such cost.
2022 SACE Stage 2-style1 markDairy-milk farmers asked the government to set a price floor (Pf) for raw milk, above the market price at the time, as a safety net against sudden falls in price. Explain the effect on the market for raw milk of setting a price floor above market price.Show worked answer →
One mark for identifying the surplus.
A price floor set above the equilibrium price is a binding minimum price. At this higher price, quantity supplied exceeds quantity demanded, so the market experiences a surplus (excess supply) of raw milk. Processing companies buy less than farmers want to sell at Pf, leaving unsold milk. (Markers accept "creates excess supply / a surplus" as the key effect; the price cannot fall to clear the market because the floor is legally enforced.)
Practise this
Sources & how we know this
- Stage 2 Economics subject outline (2025 onwards) — SACE Board
- Stage 2 Economics: external assessment — SACE Board