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S4 Economics Market Structure Practice Paper 1 | Perfect Competition, Monopoly and Oligopoly – 10 Questions with Answers
S4 Economics Market Structure Practice Paper 1 | Perfect Competition, Monopoly and Oligopoly – 10 Questions with Answers
Ten market structure questions comparing the features of four market forms, concentration ratios and the causes of monopoly, with answers and a one-line explanation.
Direct answers This paper has 10 questions covering perfect competition, monopoly, oligopoly and monopolistic competition; suggested time is 18 minutes.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 18 minutes |
| Difficulty mix | Foundation 3 · Intermediate 4 · Challenge 2 · Error redo 1 |
| Chapter | S4 Economics: Market Structure |
| Level | S4 (DSE) |
02 Questions (10 items)
- FoundationWhat are the main features of a perfectly competitive market?
- FoundationWhat is the definition of a monopoly market?
- FoundationWhat is the most typical feature of an oligopoly?
- IntermediateWhat is the key difference between monopolistic competition and perfect competition?
- IntermediateThe market shares of the four largest firms are 40%, 25%, 20% and 15%. What is the four-firm concentration ratio?
- IntermediateContinuing from the previous question, what is the Herfindahl-Hirschman Index (HHI)?
- IntermediateWhy do oligopolies often show price rigidity or collusion?
- ChallengeIn long-run equilibrium, what profit can a perfectly competitive firm earn?
- ChallengeHow does a natural monopoly arise?
- Error redoWhat is wrong with the claim that an oligopoly has many firms competing with one another?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Many buyers and sellers, a homogeneous product, free entry and exit, and perfect information on both sides. | Neither side can influence price, so firms are price takers. |
| 2 | A market with only one supplier and no close substitutes for the product. | With barriers to entry added, the monopolist can sustain this position in the long run. |
| 3 | Only a few large firms, which are mutually interdependent. | If one firm cuts price, the others must respond. |
| 4 | Products are differentiated, so firms face a downward-sloping demand curve. | Differentiation gives a firm a little pricing power. |
| 5 | 65%. | The concentration ratio adds only the four largest firms: 40 + 25. |
| 6 | 2,850. | Add the squares of the market shares: 1,600 + 625 + 400 + 225. |
| 7 | Firms are interdependent; a price cut triggers a price war, so they tend to follow or agree instead. | Collusion is mostly illegal, so non-price competition is often used in its place. |
| 8 | Only normal profit; economic profit is zero. | Free entry and exit erode supernormal profit as new firms enter. |
| 9 | Economies of scale are so large that one firm can supply the whole market at the lowest cost. | Electricity grids and water pipes are typical examples. |
| 10 | An oligopoly has very few firms; the key point is the interdependence among those few firms. | Many firms selling differentiated products describes monopolistic competition. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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