Monopoly, Price Discrimination, and Monopsony — Chapter 12 Study Materials Summary & Study Notes

📘 Overview of Monopoly

Monopoly occurs when a single firm is the sole supplier of a product with no close substitutes and entry into the market is difficult or impossible. A monopolist is a price maker and faces a downward‑sloping demand curve, so average revenue equals price ($AR = P$) and marginal revenue lies below demand ($MR < AR$).

⚖️ Sources of Monopoly Power

Common barriers to entry include legal restrictions (government‑granted monopoly franchises), patents, control of scarce resources, large sunk costs, deliberate strategic barriers (lawsuits, heavy advertising), technical superiority, and economies of scale. When a single firm can supply the entire market at lower average cost than many firms, the industry is a natural monopoly.

🧮 Monopoly Pricing and Output Decision

The monopolist maximizes profit by producing the output where marginal cost equals marginal revenue ($MC = MR$) and then choosing the price from the demand curve at that output. Because $MR$ lies below $AR$, the monopolist sells a lower quantity and charges a higher price than a perfectly competitive industry with the same costs and demand.

📉 Efficiency and Welfare Implications

Monopoly typically reduces total surplus relative to perfect competition. Under perfect competition $P = MR = MC$, but under monopoly $P > MR = MC$, so marginal benefit to consumers exceeds marginal cost at the monopoly output. The resulting deadweight loss measures the lost consumer and producer surplus due to restricted output.

🟢 Potential Benefits of Monopoly

Monopoly can sometimes foster innovation because protected firms can capture more of the returns to R&D. In natural monopolies, large scale may lower costs and thus potentially benefit consumers if regulated or priced appropriately.

💸 Price Discrimination

Price discrimination is charging different customers different prices for the same product when cost differences do not justify the price differences. Firms can increase profits by dividing customers into groups and charging each group the price that maximizes profit for that group. The profit‑maximizing rule when discriminating across groups is to set marginal revenues equal across groups: $MR_A = MR_B$, and to produce where those marginal revenues equal marginal cost ($MR_A = MR_B = MC$).

🧾 Examples and Social Effects of Price Discrimination

Examples include airline fares, movie ticket pricing, segmented tuition, and postal discounts. Price discrimination can increase firm profits and sometimes expand output (reducing deadweight loss), but it can also transfer surplus from consumers to producers and raise equity concerns.

🧭 Monopsony: Single Buyer Markets

A monopsony is a market with a single buyer of an input that has few alternative uses. A monopsonist faces an upward‑sloping supply curve for the input and a marginal input cost ($MIC$) that exceeds the supply price ($MIC > S$) because buying an additional unit requires paying a higher price on all units purchased. The monopsonist chooses input quantity where $MIC = MRP$ (marginal revenue product) and pays the input price from the supply curve.

🔁 Monopsony vs Monopoly and Efficiency

Like monopoly, monopsony leads to reduced trade relative to competitive markets and creates a deadweight loss. If a monopsony is broken into competitive buyers, the input price would rise and the quantity purchased would increase, improving total surplus.

☎️ Dynamic and Policy Considerations

Technological change (e.g., digital, satellite, and wireless communications) can undermine natural monopoly conditions by lowering replication costs. Public policy toward monopolies ranges from regulation of natural monopolies to antitrust actions and intellectual property rules that balance incentives for innovation against market power abuse.