Market failure concepts

Market failure means a market, left alone, produces a quantity or quality that does not make the most efficient use of resources. This module covers three families of cause: costs and benefits that fall on third parties, goods that cannot be sold easily, and missing information.

In the syllabus it sits between supply and equilibrium and the later topics on government and policy. Check your own examination year on the Cambridge Economics 0455 page for the exact wording of the content you are expected to know.

What should you know before starting?

You should be comfortable with demand and supply curves, equilibrium price and quantity, and the idea that a curve moves when something other than price changes. Elasticity helps when later questions ask how much quantity changes, but it is not required for the core ideas here.

You also need basic arithmetic: reading values from a table, adding costs, and finding a percentage of a total. The percentage-base explorer can help if percentage bases still trip you up.

An orienting example

A fictional farm, Ladang Hijau, sprays a crop. The spray costs the farm RM 600 a week. The drift harms a neighbour’s beehives, costing the neighbour RM 150 a week in lost honey.

• The farm’s private cost is RM 600.
• The neighbour’s loss is an external cost of RM 150.
• Social cost is 600 + 150 = RM 750.

The farm decides using RM 600. Society bears RM 750. The gap of RM 150 is why the farm sprays more than the quantity that suits everyone.

This one chain, private decision, ignored third party, wrong quantity, runs through the whole module.

In what order should you study the lessons?

1. Separate a private from an external cost: everything else relies on knowing whose cost or benefit is counted.
2. Explain under-consumption in a stated model: the mirror case, an external benefit, and the first time you work with MPB, MSB and MC together.
3. Interpret a public-good example: two defined tests and the free-rider problem.
4. Describe information failure: a different cause, hidden quality rather than third parties.
5. Compare modelled policy effects neutrally: weigh two options without taking a side.

Then do the market failure practice set with the answers closed.

What are the common traps?

• Reporting social cost as external cost. Social cost includes the producer’s own cost.
• Mixing up MPB and MSB. The market uses MPB. The social optimum uses MSB.
• Calling something a public good because the government provides it. The two tests are non-excludable and non-rival.
• Adding motives the model does not state, such as “firms are cheating” in an information failure question.
• Slipping from analysis into opinion. Evaluation names an aim and the assumptions. It does not say what governments ought to do.

How should you use the practice set?

Attempt each question on paper first. Write the final answer with its unit, then open the working and compare line by line.

Use the “If you got these wrong” section to decide which lesson to reread. Keep a note of repeated errors, because they usually come from one habit, not several.

If your diagrams are right but you still mix up private, external and social cost, a teacher in online one-to-one Economics tuition can go through your answers with you.