Monopoly

Definition

A monopoly is a market with a single seller offering a product with no close substitutes. Unlike a competitive firm, which takes the market price as given, the monopolist IS the market — it faces the entire downward-sloping market demand curve and must decide both how much to produce and what price to charge. This power to set price above marginal cost is what economists mean by market power, and it is the feature that distinguishes monopoly from competition.

The presence of a monopoly is not itself a legal violation or a moral failing. Some monopolies arise from legitimate sources — patents reward innovation, network effects naturally concentrate markets, and natural monopolies exist where a single firm can serve the market at lower cost than multiple firms. The economic concern is the deadweight loss created when price is set above marginal cost.

Why it matters

Key takeaways

The monopolist maximizes profit where Marginal Revenue = Marginal Cost (MR = MC), then charges the highest price the demand curve allows at that quantity.
Monopoly price is always above marginal cost (P > MC) — creating a wedge that prevents mutually beneficial transactions from occurring.
Deadweight loss is the value of transactions that would occur under competition but are priced out under monopoly — the social cost of market power.
Sources of monopoly power: government-granted (patents, licenses), natural monopoly (infrastructure with high fixed costs), resource control, and network effects.
Price discrimination — charging different prices to different buyers — can increase output and reduce deadweight loss while redistributing surplus from consumers to the monopolist.
The natural monopoly dilemma: a single firm is most efficient, but unregulated it over-prices; regulated to price at MC it may not cover its fixed costs.

Monopoly pricing versus competitive pricing

Read it as: Competition (green) forces price down to marginal cost — the allocatively efficient outcome. When a single seller gains market power (red), they raise price above MC and reduce quantity. The shaded region between the two represents the deadweight loss — value that could exist in the economy but doesn’t because the monopolist has priced out those transactions.

Sources of monopoly power

Government-granted monopolies

Patents give inventors exclusive rights to their invention for a limited period, creating temporary monopolies in exchange for disclosure and incentive to innovate. Copyright and licenses operate similarly. These are deliberate policy choices — trading short-term inefficiency for long-run innovation.

Natural monopoly

Some industries have very high fixed costs and low marginal costs (electricity transmission, water distribution, railroads). The total cost of serving the market is minimized when a single firm serves all customers. Multiple firms in such markets would duplicate expensive infrastructure and face higher average costs than a single firm. The dilemma: the natural monopolist, if unregulated, will still price above marginal cost.

Network effects

When the value of a product increases with the number of users (social networks, operating systems, payment systems), the largest network becomes self-reinforcing. Competitors face an insurmountable disadvantage because users go where other users already are.

Price discrimination

A monopolist who can charge different prices to different buyers can increase total output (and profit) compared to single-price monopoly. First-degree (perfect) price discrimination captures all consumer surplus and eliminates deadweight loss entirely — but requires knowledge of each buyer’s willingness to pay. Third-degree price discrimination (student discounts, airline pricing tiers, coupons) segments buyers by observable characteristics.