How do firms behave at the two extremes of market structure, and which is more efficient?
The assumptions and outcomes of perfect competition and monopoly, the short-run and long-run equilibrium of each, and a comparison of their efficiency.
A focused CCEA A-Level Economics answer on perfect competition and monopoly, covering the assumptions of each, short-run and long-run equilibrium, the role of entry and exit, the sources of monopoly power, and a comparison of allocative and productive efficiency, with worked equilibrium reasoning.
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What this dot point is asking
CCEA wants you to state the assumptions of perfect competition and monopoly, derive the short-run and long-run equilibrium of a firm in each (using the MC equals MR rule), explain the role of freedom of entry and barriers to entry, identify the sources of monopoly power, and compare the two structures on allocative and productive efficiency.
Perfect competition
In the short run the firm maximises profit where MC = MR and can earn supernormal profit (price above average cost) or make a loss (price below average cost). In the long run, freedom of entry and exit drives the adjustment: supernormal profit attracts new entrants, raising supply and lowering price until only normal profit remains (price equals average cost); losses cause exit until normal profit is restored. The long-run equilibrium is therefore at normal profit.
Monopoly
The monopolist maximises profit where MC = MR, which gives a lower output and a higher price than perfect competition. Because barriers to entry keep rivals out, it can sustain supernormal profit into the long run. Barriers to entry include economies of scale (and natural monopoly), legal barriers (patents, licences), control of an essential resource, high sunk costs, and strong brand loyalty.
Comparing efficiency
This balance is why monopoly is regulated rather than always banned, and why the case against it is conditional, not absolute.
Try this
Q1. State three assumptions of perfect competition. [3 marks]
- Cue. Many small firms, a homogeneous product, perfect information, freedom of entry and exit, price takers (any three).
Q2. Explain why a monopoly can earn supernormal profit in the long run but a perfectly competitive firm cannot. [4 marks]
- Cue. Barriers to entry protect the monopolist; free entry competes away any supernormal profit under perfect competition.
Q3. Explain one way in which a monopoly might benefit consumers. [3 marks]
- Cue. Economies of scale lowering average cost and price, supernormal profit funding research and development, or avoiding wasteful duplication as a natural monopoly.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA A2 16 marksExplain why a firm in perfect competition earns only normal profit in the long run.Show worked answer →
Worth 6 marks. Markers reward the role of freedom of entry and exit and the adjustment back to normal profit.
Assumptions: perfect competition has many small firms, a homogeneous product, perfect information and freedom of entry and exit, so each firm is a price taker.
Short run: if firms earn supernormal profit, this is a signal to outside firms.
Adjustment: because there are no barriers to entry, new firms enter the industry, increasing market supply. This lowers the market price until the supernormal profit is competed away.
Long-run equilibrium: entry stops only when firms earn just normal profit, where price equals average cost. The reverse happens if firms make losses, with firms leaving until normal profit is restored.
CCEA A2 18 marksEvaluate whether a monopoly is always against the interest of consumers.Show worked answer →
Worth 8 marks. Evaluate requires the case against and the case for monopoly with a judgement.
Case against: a monopoly maximises profit where MC equals MR, restricting output and charging a higher price than under perfect competition. It is allocatively inefficient (price exceeds marginal cost) and may be productively inefficient and complacent (X-inefficiency), reducing consumer surplus.
Case for: a monopoly can use economies of scale to lower average cost, so price may be lower than many small firms could achieve. Supernormal profit can fund research and development and innovation, and a natural monopoly avoids wasteful duplication.
Judgement: monopoly is not always against consumers; it depends on whether economies of scale and innovation outweigh the higher price and restricted output, and on whether the firm is regulated or contestable, so the outcome is case-specific.
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Sources & how we know this
- CCEA GCE Economics specification — CCEA (2016)