Monopoly: Market Power, Pricing, and Policy (Chapter 12)
12.1 Introducing a New Market Structure
Perfectly competitive markets are a special case where firms are price-takers (they take the market price as given). A more common, real-world market structure features price-makers—firms that can set the price of a good.
Monopoly is the extreme market structure: a single seller with no close substitutes, giving the firm substantial market power to influence price.
Key contrast: price-takers vs price-makers influence the price; the firm’s demand facing a monopolist is downward-sloping, whereas a perfectly competitive firm faces a horizontal (infinite-elasticity) demand curve.
Exhibit 12.1 (conceptual): Perfect Competition vs Monopoly
Perfect Competition: many firms, identical products, no barriers to entry, price-taker, P = MR = MC, horizontal demand facing a firm, socially efficient outcome in long run (zero economic profits).
Monopoly: one firm, unique product or no close substitutes, high barriers to entry, price-maker, P > MR = MC, downward-sloping demand facing the firm, possible positive profits in long run, potential deadweight loss to society.
Implications for efficiency and welfare depend on the structure; monopolies can reduce total surplus relative to competitive benchmarks but can also spur innovation in some contexts (to be explored in evidence-based sections).
12.2 Sources of Market Power
Barriers to entry are circumstances that prevent potential competitors from entering the market.
Types of barriers to entry include:
1) Legal market power: government-granted rights that restrict competition (e.g., patents, copyrights).
2) Natural market power: arises from economics of scale or control of key resources.
3) Control of key resources: essential inputs controlled by one firm (e.g., Alcoa and bauxite; De Beers and diamond production).
4) Economies of scale: large fixed costs and scale economies that deter new entrants; natural monopolies arise when a single firm can supply the entire market at lower cost than multiple firms.
5) Network externalities: value of a product increases as more people use it (eBay, Facebook, Instagram) — raises barriers for new entrants.
Evidence/Examples discussed:
Legal power: patents and copyrights create temporary monopoly rights.
Turing Pharmaceuticals example: large entry barriers due to regulatory approvals (FDA) and time to develop generics, allowing a dramatic price increase for a drug (e.g., Daraprim).
Natural power and network externalities illustrate why some markets tend to be dominated by a single firm for extended periods.
Summary takeaway: Market power often arises from both natural market forces and government-protected rights; understanding these sources helps explain why monopolies emerge and persist.
12.3 The Monopolist’s Problem
Goal of any firm (monopolist or price-taking firm): understand how inputs combine to make outputs and know the production costs.
Key question: Can a monopolist charge any price it wants? The answer is no: profits maximize where marginal revenue (MR) equals marginal cost (MC). The price charged is the price corresponding to that quantity on the demand curve.
Revenue concepts:
Total Revenue: TR(Q) = P(Q)\cdot Q
Marginal Revenue: MR(Q) = \frac{d\,TR(Q)}{dQ}
Profit: \pi(Q) = TR(Q) - TC(Q)
Average Total Cost: ATC(Q) = \frac{TC(Q)}{Q}
Monopolist vs perfect competitor in terms of pricing:
Monopolist: sets output where MR = MC; price is determined from the demand curve at that quantity; typically, P > MR.
Perfectly competitive firm: sets output where P = MR = MC; price is taken from the market; firm’s demand is perfectly elastic.
Exhibit 12.3 (conceptual): Demand curves faced by the two types of firms
Perfect competition faces a horizontal demand curve; monopoly faces a downward-sloping demand curve.
Why MR ≠ Price for a monopolist:
For a downward-sloping demand, to sell one more unit, must lower price on all previous units sold (causing MR < Price). In many cases with linear demand, MR is steeper and lies below the price curve.
12.4 Choosing the Optimal Quantity and Price
The steps the monopolist follows to maximize profit:
Determine the revenue function: TR(Q) = P(Q)\cdot Q and the marginal revenue: MR(Q) = \frac{d(TR)}{dQ}.
Determine the cost function: TC(Q) with marginal cost MC(Q) = \frac{dTC}{dQ} and average cost ATC(Q) = \frac{TC(Q)}{Q}.
Find the quantity where MR(Q) = MC(Q). If multiple solutions, choose the one that yields the highest profit.
Use the demand curve to find the corresponding price: P = P(Q).
Check profit: \pi(Q) = TR(Q) - TC(Q); ensure second-order conditions hold (dMR/dQ < dMC/dQ around the optimum).
Example: Claritin (Exhibit 12.5, 12.6, 12.7)
Data points illustrate TR, MR, TC, MC, ATC across quantities 100 to 1,100 (in millions of pills).
At Q = 500, Price P = 3.50; Total Revenue TR = 1{,}750; Total Cost TC = 510; Marginal Cost (constant) MC = 1.00; Marginal Revenue at 500 is MR = 1.
Profit maximizing condition MR = MC holds at Q = 500 (since MR decreases with Q and MC is constant at 1).
Profit: \pi = TR - TC = 1{,}750 - 510 = 1{,}240 (in millions of dollars). Price at optimum: P = 3.50.
Key takeaway: For a monopolist, the profit-maximizing quantity is where MR = MC and the price is found from the demand curve at that quantity. The monopolist typically earns positive profits due to P > MC and the absence of competition.
The Monopolist’s Problem (8–10) highlights the interplay between the quantity effect (selling more units) and the price effect (lower price to sell additional units), which together determine MR and thus the optimal output.
Does a monopoly have a supply curve?
No: a monopoly is not a price taker; it faces a downward-sloping demand curve and chooses quantity based on MR = MC. Therefore, there is no single, well-defined supply curve for a monopoly.
How profits are computed in the Claritin example (summarized):
Profit = TR − TC; where TR = P(Q)×Q and MC is the derivative of TC with respect to Q. Using MR = MC gives the optimal Q, then P from the demand. The example yields a positive profit at Q = 500 with P = 3.50 and π = 1.24 billion.
12.5 The “Broken” Invisible Hand: The Cost of Monopoly
Social surplus under monopoly is typically lower than under perfect competition due to the deadweight loss created by restricting output and charging a higher price.
Exhibit 12.11 (Surplus Allocations: Perfect Competition versus Monopoly) illustrates how the allocation of surplus differs between the two structures:
Under perfect competition: total surplus (CS + PS) is maximized; no DWL.
Under monopoly: some of the potential gains from trade are not realized, creating a DWL triangle and a redistribution of surplus from consumers to the monopolist.
The key intuition: Monopoly restricts output to raise price, reducing consumer surplus and transferring some surplus to the producer, but not all gains are captured because output is below the social optimum.
12.6 Restoring Efficiency
Price discrimination is one of the main tools to restore efficiency in monopolies by transferring more surplus to the producer and reducing or eliminating deadweight loss.
Three degrees of price discrimination:
First-degree (perfect) price discrimination: charge each consumer their maximum willingness to pay; outcomes:
Consumers’ surplus is eliminated; all surplus goes to the producer; total surplus equals the producer’s profit. No DWL.
Examples: personalized car pricing, some eBay transactions where the seller can extract the entire willingness to pay.
Second-degree price discrimination: price varies by quantity or version of the product, not by who is buying; examples include bulk discounts, block pricing, or versioning products.
Third-degree price discrimination: price varies by consumer characteristics or location (e.g., senior discounts, student discounts, matinee prices).
Why firms use price discrimination:
If firms can segment markets and prevent arbitrage, they can capture more of the total surplus as profit and potentially increase overall output efficiency.
Practical questions:
What if firms don’t know a consumer’s willingness to pay? Firms may use proxies (ages, student status, regional pricing) or employ dynamic pricing/discounts and rebates to approximate effective discrimination.
Rebates vs up-front discounts: rebates can serve as a form of price discrimination or consumer segmentation; they affect perceived price and consumer behavior differently than upfront discounts.
The goal of price discrimination in this framework is to reduce or eliminate the deadweight loss associated with uniform monopoly pricing, potentially increasing total welfare if implemented under credible market segmentation.
12.7 Government Policy toward Monopoly
Antitrust policy aims to prevent anti-competitive pricing, low output, and deadweight loss from dominant markets.
Sherman Act (1890): prohibits restraints on trade and attempts to monopolize markets; violations can be illegal and subject to penalties.
Case example: Microsoft faced allegations of restraint of trade by bundling Windows with Internet Explorer and attempting to exclude competitors; the outcome:
The firm was not broken up into two separate firms (OS vs applications), but it had to change practices and make it easier for other browsers to work with Windows.
Pricing regulation as an alternative to anti-trust action:
Efficient (socially optimal) price: P = MC
Fair-returns price: P = ATC
The choice between antitrust enforcement and price regulation reflects different policy tools to address market power and its welfare consequences.
Exhibit 12.11 (surplus allocations) recurs here as a reference point for policy impact on welfare under competition vs monopoly.
Evidence-Based Economics: Can a monopoly be good for society?
Evidence suggests that market power can be an important driver of innovation in many settings, especially when there are brilliant competitors to imitate and spur innovation.
The strongest case for monopolies as efficiency-enhancing occurs in industries where competition among many firms is hard to sustain yet where there is meaningful innovation/research that benefits from concentrated teams of innovators.
Case study: Claritin problem (patent-protected monopoly vs competition)
Problem setup: An allergy drug with constant marginal cost MC = 5; the annual demand and marginal revenue are given by a curve with MR and a downward-sloping demand.
a) In a competitive market with many firms, determine equilibrium price, quantity, consumer surplus (CS), and producer surplus (PS).
b) Under a patent (monopoly), determine the monopoly price and quantity.
c) Compare CS and PS under both scenarios; assess welfare implications.
Evidence-Based Economics Problem (Claritin) – Summary of setup and results
Given data (illustrative):
Demand and MR figures: MR takes the values 5, 4, 3, 2, 1, 0, -1, -2, -3, -4, -5 as quantity rises from 100 to 1,100 (units in millions).
Price schedule: starts at $5.50 when Q = 100 and falls to $0.50 at Q = 1,100.
Total Revenue (TR) and Marginal Revenue (MR) are computed from the price schedule; MC is constant at $1; ATC values are shown (ranging around ~1.01 to 1.10 across outputs).
Fixed cost given (e.g., 10 in the table, with MC = 1).
Key result from the monopoly exercise (as shown in the example for Claritin):
The profit-maximizing output occurs where MR = MC, which in the table occurs around Q = 500 (MR = 1, MC = 1).
Corresponding price is P = $3.50; TR = $1{,}750; TC = $510; Profit = TR - TC = $1{,}240 million (i.e., $1.24 billion).
This example illustrates how the monopolist’s choice (MR = MC) differs from competitive pricing, yielding a higher price and lower quantity than perfect competition but generating positive profits.
Takeaway: Patent protection can create monopoly power, affecting prices, quantities, and welfare; policy may balance incentives for innovation with consumer welfare through regulation, competition policy, and potential price regulation.
Practical Implications and Connections
The market power discussion ties to real-world questions about price-setting, access, and innovation (e.g., drugs, tech platforms, natural monopolies).
The policy toolkit (antitrust vs regulation) yields different welfare outcomes and depends on market structure, measurement of costs, and regulatory feasibility.
Price discrimination offers a potential mechanism to improve efficiency, but it requires credible ability to segment markets and prevent arbitrage; ethical and equity considerations also arise when charging different prices to different groups.
Network externalities and control of key resources can create barriers to entry that sustain monopolies, highlighting why some markets remain concentrated even in the absence of explicit collusion.
Quick Reference: Core Formulas and Concepts
Demand facing a monopolist: downward-sloping; price depends on quantity through the demand curve P(Q).
Total Revenue: TR(Q) = P(Q) \cdot Q
Marginal Revenue: MR(Q) = \frac{d(TR)}{dQ}
Total Cost: TC(Q); Marginal Cost: MC(Q) = \frac{dTC}{dQ}; Average Total Cost: ATC(Q) = \frac{TC(Q)}{Q}
Profit: \pi(Q) = TR(Q) - TC(Q)
Profit-maximizing condition for a monopolist: MR(Q^) = MC(Q^) with price determined from the demand curve at Q^; typically, P(Q^) > MR(Q^*)
Profit-maximizing condition for a perfectly competitive firm: P = MR = MC with price taken from the market.
Deadweight loss under monopoly: DWL is the triangular area between the demand and marginal cost curves for the units that are not produced due to monopoly output; can be expressed as an integral: DWL = \int{Qm}^{Qc} [P(Q) - MC(Q)]\,dQ where Qm is monopoly quantity and Q_c is competitive quantity.
Price discrimination degrees:
First-degree: charge each consumer their maximum willingness to pay; CS = 0; all surplus captured as profit.
Second-degree: price varies by quantity or version; e.g., bulk discounts.
Third-degree: price varies by consumer characteristics or location (student discounts, senior discounts).
Policy tools:
Antitrust: Sherman Act; prevents restraints on trade and monopolization.
Price regulation: P = MC (allocative efficiency) or P = ATC (normal profits).
Regulatory choice depends on market structure and feasibility.
Notes
This set of notes covers the content from the Monopoly chapter slides, including the definitions, the monopolist’s problem, the optimal pricing and quantity, the welfare implications of monopoly, price discrimination, and government policy toward monopoly.
The Claritin example provides concrete numerical illustration of MR = MC decision rule and profit computation in a monopoly context.
Real-world examples (e.g., Daraprim price hike by Turing Pharmaceuticals) illustrate how barriers to entry and strategic pricing affect welfare and policy.