2.28 - Monopoly

The characteristics and market power of monopolies

A monopoly exists in a market where a single firm supplies a product or service, making it the dominant player. This market structure features unique products and significant barriers that prevent new firms from entering.

Key features of a monopoly

• Single dominant firm - One company controls the entire market supply, often producing goods or services seen as having no close substitutes.
• High barriers to entry - These obstacles, such as legal restrictions, high startup costs, or control over essential resources, stop potential competitors from joining the market.
• Market power - The monopolist acts as a price setter, facing a downward-sloping demand curve for the whole market, which gives it the ability to influence prices.

Monopolists have considerable control over the market but are still limited by consumer demand: they must balance output levels with the prices buyers are willing to pay.

Sources of monopoly power

• State-created barriers - Governments may grant exclusive rights, such as patents or licences, to protect innovation or ensure service quality.
• Firm strategies - Some monopolists maintain their position through tactics like aggressive pricing or lobbying.
• Natural monopolies - In industries like utilities, a single firm is more efficient than multiple ones, as duplicating infrastructure (e.g., water pipes) would lead to wasteful costs.

Pricing, output, and profit maximisation

Monopolists decide on prices and output to achieve their goals, typically focusing on maximising profits. Unlike firms in competitive markets, they can sustain high earnings over time due to entry barriers.

How monopolists set prices and output

Monopolists produce at the output level where marginal revenue (MR) equals marginal cost (MC). The diagram below shows this: MR cuts MC at point H, which fixes output at Qm. They then set the price based on the demand curve at that output point, so reading up from Qm to the demand curve (D, AR) gives point B and a price of Pm. This approach allows them to charge more than their production costs but prevents them from freely choosing both price and quantity independently.

Profit levels in monopolies

• Supernormal profits - Average cost at Qm is C, read off the average cost curve (AC) at point A, so every unit sold earns Pm minus C and total profit is the shaded rectangle between C, A, B and Pm. Monopolists can earn profits above normal levels (also called abnormal profits) in both the short and long run, as barriers block new entrants who might erode these gains.
• Constraints on profits - While profits can be high, they depend on demand: if consumers reject high prices, sales may fall, limiting overall earnings.

Inefficiencies and welfare loss in monopolies

Monopolies often lead to less efficient outcomes compared to more competitive markets, resulting in higher costs for society and reduced overall welfare. The diagram below takes the same monopolist, producing Qm where MR meets MC and charging Pm, and adds the output Qsoc that society would have wanted.

Types of inefficiency in monopolies

• Allocative inefficiency - Occurs because the monopolist sets prices above marginal cost (P > MC). At Qm the price is Pm at point B while marginal cost is only the height of point H, so output stops well short of Qsoc, where the demand curve (D, AR) crosses MC at point F. That leaves underproduction and resources not being allocated to meet consumer needs fully.
• Technical inefficiency - Without competitive pressure, monopolists may not minimise average costs: at Qm the firm is still on the falling part of its average cost curve (AC) rather than at its lowest point, producing less efficiently than firms in competitive environments.

The concept of welfare loss

Welfare loss, or deadweight loss, arises when monopolists restrict output below the level where price equals marginal cost, reducing total social benefits. Every unit between Qm and Qsoc is worth more to buyers than it costs to produce, and the value society never gets is the shaded welfare loss triangle H, B, F. This creates a gap between what society could gain from efficient production and what actually occurs.

Potential benefits of monopolies

Despite inefficiencies, monopolies can offer advantages in certain situations:

• Economies of scale - Large monopolists can produce at lower average costs by spreading fixed expenses over high output volumes.
• Innovation incentives - Supernormal profits allow investment in research and development (R&D), leading to new products or technologies.
• Efficiency in natural monopolies - A single provider avoids wasteful duplication, such as in rail networks, benefiting society through lower overall costs.

Comparison of monopolies with perfect competition

Monopolies and perfect competition represent opposite ends of market structures. Assuming identical cost conditions, key differences emerge in output, pricing, and efficiency.

Key differences between monopoly and perfect competition

Where:

• Qm - Quantity under monopoly
• Qc - Quantity under perfect competition
• Pm - Price under monopoly
• Pc - Price under perfect competition
• P - Price (general)
• MC - Marginal cost

In perfect competition, many firms produce identical products with free entry and exit, leading to efficient outcomes. Monopolies, by contrast, limit competition, resulting in higher prices and lower output.

Surpluses in monopoly and perfect competition

• Consumer surplus - The benefit consumers gain, measured as the area below the demand curve and above the price paid. It is smaller in monopolies due to higher prices.
• Producer surplus - The benefit producers receive, measured as the area above the marginal cost curve and below the price received. It is usually larger in monopolies.
• Social surplus - The total of consumer and producer surplus, which is reduced in monopolies, creating welfare loss. Monopolies also transfer income from consumers to producers through higher prices.

Both outcomes fit on one diagram, because the cost conditions are assumed to be the same. In the competitive market, demand D meets supply S, MC (the supply curve also reflects marginal cost) at price Pc and quantity Qc. Monopolise that market and the firm produces where MR meets S, MC, so output falls to Qm and the price rises to Pm. The curves and the price and quantity lines cut the space into eight areas, and numbering them 1 to 8 lets each surplus be read off directly.

Consumers lose areas 3, 4 and 5. The firm gives up area 8 but gains the larger 3 + 4, so it ends up better off. Areas 5 and 8 are made in perfect competition and not under monopoly, so together they are the welfare loss, while 3 + 4 is income transferred from consumers to the monopolist rather than value destroyed.

Measuring monopoly power and its impacts

Monopoly power refers to a firm's ability to set prices above marginal cost, which can be quantified and has broader economic effects.

The Lerner index

The Lerner index calculates the degree of monopoly power as follows:

$$\text{Lerner index}=\frac{\text{P}-\text{MC}}{\text{P}}$$

Where:

• P = Price charged
• MC = Marginal cost

In perfect competition, the index is 0 (P = MC, no power). Higher values indicate stronger monopoly power, often linked to fewer substitutes available for the product.

Impacts on income inequality

Monopolies can worsen income inequality by charging high prices, which transfers wealth from consumers (often lower-income groups) to firm owners or shareholders. This redistribution increases the gap between rich and poor, as supernormal profits benefit a small group while raising costs for everyone else.