Difficulty: Introductory to Intermediate | Prerequisites: Parts 1 and 2 of these notes
Part 3 of three covering Chapter 11 of Perloff's Microeconomics (5th Ed.). This part covers Section 11.4: why monopolies arise, including cost advantages, natural monopoly, government actions, patents, and licensing.
Monopolies arise from two broad sources: cost advantages (the firm can produce more cheaply than any rival) and government actions (patents, licences, public utility franchises). A natural monopoly exists when one firm can serve the whole market at lower total cost than two or more firms could, typically because of high fixed costs and constant or declining marginal costs. Governments grant patent monopolies as a deliberate trade-off, accepting short-term deadweight loss in exchange for long-term incentives to innovate.
Natural monopoly
A market in which one firm can produce the total market output at a lower total cost than any combination of two or more firms. Formally: C(Q) < C(q1) + C(q2) + ... + C(qn) for all ways of splitting Q among n >= 2 firms.
In simple terms: it is cheaper to have one producer than several, usually because of large fixed costs that would be duplicated.
Essential facility
A scarce resource controlled by one firm that rivals need access to in order to compete. Owning the only quarry in a region, or the only pipeline network, can give a firm monopoly power.
Think of it as: the one piece of infrastructure everyone else needs but only one firm owns.
Patent
An exclusive right granted by government to the inventor of a new and useful product, process, or design, allowing the inventor to be the sole seller for a fixed period. In the US, patents now last 20 years from the filing date.
In simple terms: a legal monopoly given to inventors so they can recoup their R&D costs before competitors copy them.
Copyright
Similar to a patent, but for artistic, literary, dramatic, or musical works. Gives the owner exclusive production, publication, or sales rights.
Public utility
A provider of essential services (water, gas, electricity, mail) that is granted monopoly rights by the government, usually because the market is believed to be a natural monopoly. The government may regulate the utility's prices or capture some of its profits through franchise fees.
Economies of scale
A cost structure where average cost falls as output increases. If economies of scale persist at all output levels, the market is a natural monopoly because a single firm always has a lower average cost than multiple smaller firms.
Think of it as: making more of something makes each unit cheaper, because the fixed costs get spread across more units.
A firm becomes a monopoly through cost advantages when it can profitably sell at a price so low that no rival can enter without incurring losses. Three sources:
Essential facility. The firm controls a scarce resource rivals need. Example: the only quarry in a region, or the only pipeline network connecting producers to markets.
Superior technology or organisation. A firm with better production methods has lower costs. Example: Henry Ford's assembly-line methods gave him a cost advantage over rivals until they adopted the same techniques.
Natural monopoly. One firm can produce the entire market output more cheaply than any combination of multiple firms.
The formal condition is C(Q) < C(q1) + C(q2) + ... + C(qn) for all possible splits of total output Q among n >= 2 firms.
A sufficient (but not necessary) condition: the firm has economies of scale at all output levels, meaning average cost falls continuously.
The typical case is a firm with high fixed costs and constant marginal cost. Total cost: C(Q) = mQ + F. Average cost: AC = m + F/Q, which declines as Q rises.
Example: a water utility with F = $60 and m = $10. One firm producing 12 units has AC = $15 (total cost $180). Two firms each producing 6 units have AC = $20 each (total cost $240). The single firm is cheaper by exactly F = $60, the duplicated fixed cost.
With two firms, the marginal cost per unit is the same, but total fixed costs are doubled. Every additional firm adds another layer of fixed cost.
Licences and entry restrictions. Governments require licences to operate in many industries. If obtaining a licence is difficult, the first firm to get one can maintain its monopoly. Certificates of need (for hospitals), broadcast licences, and taxi medallions are examples.
Public utility franchises. Instead of running a utility directly, a government grants a private company the monopoly right to operate it. The government may charge a franchise fee or regulate the monopoly's prices.
Auctions. Governments sometimes auction monopoly rights to private firms. A welfare-maximising approach is to auction the right to the firm that offers the lowest consumer price.
Patents. Patents give inventors 20 years of monopoly protection (from the filing date in the US) as an incentive for costly R&D. The government explicitly trades short-term deadweight loss against long-term innovation benefits. Without patents, firms would have less incentive to spend hundreds of millions developing new drugs or technologies.
Copyrights. Similar logic to patents, but for creative works.
Patents create monopoly pricing and deadweight loss during their term. The justification is that without patent protection, the expected return on R&D investment falls, so fewer inventions happen. The costs of developing a new drug or computer chip can run into billions of dollars. If anyone could immediately copy and undercut the inventor, few would invest in the research. The patent system is a deliberate policy choice, not an accident.
Water utilities. A water company must build a plant and lay pipes to every house (high F). The marginal cost of delivering water is roughly constant. One firm serving a city has AC = m + F/Q. A second firm would duplicate the entire infrastructure, doubling fixed costs for no reduction in marginal cost. This is why water is almost always a regulated monopoly.
Pharmaceutical patents. Developing a new drug can cost over $1 billion. Plavix, Harvoni, and Daraprim all illustrate patent monopolies charging prices far above marginal cost. When patents expire, generic entry drives prices toward MC, but brand-name prices sometimes rise as the remaining loyal customers are less price-sensitive.
Botox. Allergan's patent on botulinum toxin for cosmetic use gave it a near-monopoly. With MC of about $25 and a selling price of $400, the elasticity of demand was only about -1.07. The near-absence of close substitutes explains the extreme pricing power.
"Natural monopoly means the firm is big." A natural monopoly is defined by cost structure (one firm produces more cheaply than multiple firms), not by absolute size. A small local water company serving a village is a natural monopoly if duplicating its pipes would raise total cost.
"Patents are unfair because they create monopolies." Patents do create monopoly pricing and deadweight loss, but this is a deliberate policy trade-off. Without patents, firms would have far less incentive to invest billions in R&D. The question is whether the patent length is set correctly, not whether patents should exist at all.
"If average cost is falling, the firm must be a natural monopoly." Economies of scale everywhere are sufficient for a natural monopoly, but not necessary. A firm can be a natural monopoly even if its average cost curve is U-shaped, provided the efficient scale is large enough relative to market demand.
"Government-created monopolies are always harmful." Public utilities, postal services, and patent systems are government-created monopolies designed to serve a purpose, whether that is avoiding wasteful duplication of infrastructure or incentivising innovation. The welfare effects depend on how the monopoly is regulated.
True or False: A natural monopoly requires that the firm's average cost curve be declining at all output levels. (False. Declining AC everywhere is sufficient but not necessary for a natural monopoly.)
Fill in the blank: US patents now last ____ years from the ____ date. (20, filing)
True or False: An essential facility is a resource that many firms in a market share equally. (False. An essential facility is a scarce resource controlled by one firm that rivals need to compete.)
Fill in the blank: The key reason natural monopoly arises with C(Q) = mQ + F is that each additional firm duplicates the ____. (fixed cost, F)
Q: A firm delivers water with total cost C(Q) = 8Q + 100. A potential entrant has the same cost function. Show that this market is a natural monopoly.
A: If two firms split output, their combined cost is C(q1) + C(q2) = 8q1 + 100 + 8q2 + 100 = 8(q1 + q2) + 200 = 8Q + 200. A single firm produces Q at cost 8Q + 100. The single firm is cheaper by 100 (one avoided fixed cost). This holds for any split, so the market is a natural monopoly.
Q: Name two cost-based sources of monopoly power and one government-based source.
A: Cost-based: (1) control of an essential facility, (2) natural monopoly (economies of scale). Government-based: patents (or equivalently, licensing restrictions or public utility franchises).
Q: Why might a government grant a monopoly to a water company rather than allowing free entry?
A: Water delivery has large fixed costs (plant, pipes) and roughly constant marginal cost, making it a natural monopoly. Multiple firms would each duplicate the fixed infrastructure, raising total industry cost without reducing the cost per unit of water. The government grants a monopoly to avoid this wasteful duplication, then typically regulates the firm's prices to prevent monopoly pricing.
Q: Explain the trade-off involved in granting patent monopolies.
A: Patents cause short-term welfare loss through monopoly pricing and deadweight loss. However, without patent protection, inventors could not recoup the often enormous R&D costs (hundreds of millions to billions of dollars for a new drug). Competitors would copy and undercut them immediately. The patent system accepts short-term inefficiency as the price of long-term innovation incentives.
Natural monopoly connects to the cost theory in Chapter 7 (economies of scale, fixed vs variable costs, average cost curves). Government regulation of monopolies (price setting, allowing entry) is covered in Section 11.5. In later chapters, barriers to entry reappear in oligopoly (Chapter 13) and cartel behaviour (Chapter 14). Network externalities as a source of monopoly (Section 11.6) connect to behavioural economics and the economics of platforms.
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