The lesson
Explain the mechanism, then qualify the outcome. Use this page as a fast, high-quality revision pass—not a wall of notes to memorise.
How structures differ
Market structure describes the conditions in which firms compete, including the number and size of firms, product differentiation and barriers to entry.
- Perfect competition is a benchmark with many firms and no individual price control.
- Monopoly involves one dominant supplier with significant barriers to entry.
- Oligopoly involves a few interdependent firms whose decisions affect one another.
Efficiency is not one thing
A market may offer lower prices and choice, but firms also need incentives and finance to invest.
- Allocative efficiency concerns whether price reflects marginal cost.
- Productive efficiency concerns producing at the lowest average cost.
- A monopoly may exploit market power, but economies of scale or innovation can sometimes provide benefits.
Worked exam thinking
Worked example: a natural monopoly
Prompt: Why might a regulator intervene in a natural monopoly?
How to turn knowledge into marks
Use this answer route
For a focused explanation or short evaluation question on this topic:
- 1Define the core idea precisely.
- 2Explain the chain of cause and effect.
- 3Apply it to the context in the question.
- 4Evaluate a limitation, trade-off or condition.
Quick questions
Check your understanding
What is a barrier to entry?
Anything that makes entry difficult or costly, such as patents, high start-up costs or control of key resources.
What is an oligopoly?
A market dominated by a small number of interdependent firms.
Can monopoly ever benefit consumers?
It can benefit consumers if scale economies, investment or innovation outweigh the risks of higher prices and restricted output.