Explain market failure and misallocation
Connect public goods, merit and demerit goods, externalities and monopoly with over- or under-allocation.
Section 2.9 · Market failure
Cambridge IGCSE Economics 0455 / IGCSE (9–1) Economics 0987, 2027–2029 Version 1. Apply each model to the stated evidence and qualify conclusions where effects depend on context. Practice is original and self-checked; it is not a Cambridge paper, mark scheme or official grade.
Before you begin
- No prior economics study is assumed. Read the scenario for the decision-maker, the market or economy involved, the time period and the evidence supplied.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why may a public good be underprovided by private sellers?
What you will learn
- Define market failure
- Distinguish private and social effects
- Explain consequences of misallocated resources
Private choices can omit wider effects
Market failure occurs when market allocation misallocates resources relative to a social objective. Private benefits and costs affect a buyer or seller; external benefits and costs affect third parties. Social benefit equals private benefit plus external benefit, and social cost equals private cost plus external cost.
Merit goods may generate external benefits; demerit goods may generate external costs. Public goods are non-rival and non-excludable in the standard definition, which can make it difficult for private sellers to charge each beneficiary.
Trace the consequence, not just the label
If external costs are ignored, a good may be over-consumed; if external benefits are not fully reflected in demand, a good may be under-consumed. Public goods may be underprovided or not provided, and monopoly power can restrict supply and raise prices.
Market failure does not prove that every government intervention will improve outcomes. Compare the likely benefit with information, administration and unintended costs. Cambridge does not require demand-and-supply diagrams for market failure in this syllabus version.
Pause and explain
A firm restricts output under monopoly and charges more. Which market-failure consequence is illustrated?
Worked example
A vaccination programme reduces disease transmission to people who are not vaccinated. Explain the external benefit and likely market outcome.
Show the worked solution
- The health benefit reaches third parties.
- Private buyers may not consider the full social benefit.
- Voluntary market demand may be below the socially preferred level.
Answer The programme creates an external benefit for others. If buyers consider only private benefits, uptake may be lower than the level that accounts for total social benefits.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A factory's noise affects nearby residents who are not part of the sale. Classify the cost and explain why the market price may omit it.
Give me a hint
Identify who bears the cost and whether they are a party to the transaction.
Compare my reasoning
- Residents are third parties.
- Noise is an external cost if not compensated or included.
- The market price may reflect only costs paid by the firm and buyer.
It is a negative external cost if residents bear harm outside the transaction. A market price based only on private costs may omit that damage.
Look for these in your work
- Third party named
- External cost classified
- Price omission explained
A city funds street lighting that benefits pedestrians and drivers. Explain why a private supplier may not capture all benefits.
Give me a hint
Consider whether use is rival and whether people can be excluded.
Compare my reasoning
- Many people benefit from the same lighting.
- It can be difficult to exclude non-payers.
- The supplier may struggle to charge each beneficiary, risking underprovision.
Street lighting can benefit many users who are hard to exclude. Because the supplier may not capture all benefits through sales, private provision could be below the socially preferred level.
Look for these in your work
- Shared benefit identified
- Exclusion considered
- Underprovision linked
A government proposes a tax to reduce a polluting activity. Explain one expected benefit and one reason the policy may not fully correct the market failure.
Give me a hint
Consider incentives and information about the external cost.
Compare my reasoning
- A tax can raise the private cost of polluting.
- Firms may reduce or clean up production.
- The tax level and enforcement may be imperfect or costly.
The tax may make firms consider more of the external cost and reduce pollution. If the damage is hard to measure or enforcement is weak, the tax may not achieve the intended reduction and could impose other costs.
Look for these in your work
- Incentive mechanism explained
- Response identified
- Policy limitation explained
Common mistakes
- Calling every benefit external
- Confusing a merit good with a public good
- Assuming intervention has no cost or failure risk
What can you explain now?
What does market failure describe?
Compare with the explanation
A misallocation relative to a social objective
It concerns how resources are allocated, not just a price change.
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Make it stick
What does market failure describe?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.