2.11 Market failure - market power (HL only)

Market failure is not simply supernormal profit or high prices; it requires a net loss of social welfare relative to the allocatively efficient outcome, which occurs when P ≠ MC, so resources are misallocated.

In perfect competition, every firm is a price taker with P = MR, so the profit-maximising rule MC = MR also gives MC = P. Resources are allocated to their highest-valued uses, and total welfare is maximised.

A monopolist faces a downward-sloping demand curve, so MR < P at every output. Profit maximisation at MC = MR yields quantity $Q_m$ where P > MC, meaning consumers value extra units more than they cost to produce, yet those units go unproduced — a net welfare loss.

The correct option states that the monopolist restricts output below the allocatively efficient quantity and charges P > MC, generating a net welfare loss — the precise definition of market failure. This is distinct from the mere redistribution of surplus from consumers to the firm, which on its own is not a welfare loss.

The question asks why the monopolist's outcome is market failure while the competitive firm's is not. The key distinction is allocative efficiency (P = MC) versus allocative inefficiency (P > MC).

'Earning supernormal profit is itself defined as market failure' is incorrect. A firm can earn supernormal profit without causing market failure if it produces at the allocatively efficient quantity; profit level is not the criterion for market failure.

The claim that 'persistent profit equals market failure' confuses the source of market power (barriers to entry) with the outcome (allocative inefficiency). Barriers are a cause, not the definition, of market failure.

The transfer of consumer surplus to the monopolist (the rectangle between $P_c$ and $P_m$ up to $Q_m$) is a redistribution, not a net loss — the firm gains what consumers lose. Redistribution alone is not market failure.

The remaining option correctly identifies that the monopolist produces where P > MC, restricting output below the social optimum and generating a deadweight loss — units not produced that consumers valued more than their cost — which is the net welfare loss defining market failure.

The firm changes nothing about the physical product — materials and construction are unchanged. The investment is in advertising, logo, and sponsorship: these are tools of branding, which aims to create a perceived difference in the minds of consumers rather than an actual functional difference.

Successful branding generates brand loyalty: consumers habitually choose this brand over functionally identical rivals and are willing to pay a premium. This makes the firm's demand curve less price elastic — consumers are less responsive to price increases because they feel the brand is distinct.

Because demand is less elastic, the firm can raise its price above the competitive level and still retain a substantial customer base. This is the essence of market power: the ability to sustain price above the competitive benchmark without losing all customers.

The correct option directly captures the branding mechanism: perceived differentiation reduces price elasticity, allowing the firm to sustain a price premium. This matches the scenario, which explicitly states no actual quality change occurred.

The question distinguishes branding (perceived difference, no real change) from quality differentiation (actual improvement), economies of scale (cost advantage), and legal barriers (law-based). The scenario emphasises advertising and image with no product change.

'Quality differentiation improves the actual durability of the garments' is directly contradicted by the scenario, which states materials and construction are unchanged. Quality differentiation requires a verifiable functional improvement, not just a perception.

There is no mention of cost advantages or large-scale production. Economies of scale relate to falling average costs with increased output, not to advertising or logo investment — these are unrelated mechanisms.

While trademark law does protect logos, the scenario is about the market power created by consumer loyalty from advertising, not about the legal protection itself. Trademark registration does not restrict other firms from selling clothing — it only prevents copying of the specific logo.

The branding option correctly identifies that the strategy creates perceived differentiation, reduces price elasticity, and thereby allows a sustained price above the competitive level — which is the definition of market power generated through branding.