Sources of Monopoly Power

A monopoly is a market served by one seller without a close substitute. The definition depends on the relevant product and geographic market: one bakery may be alone on a street but still compete with supermarkets, delivery platforms, and home cooking.

Having one seller today does not guarantee durable market power. The key question is why rivals cannot enter or buyers cannot switch.

Four common barriers

• Legal protection: patents, copyrights, licenses, or exclusive concessions restrict who may supply.
• Control of an essential input: one firm controls a resource, location, standard, or dataset that entrants need.
• Network effects and switching costs: a service becomes more useful as others join, while moving data or contacts is costly.
• Economies of scale: average cost falls across most market demand, so duplicating infrastructure is expensive.

Barriers can have mixed purposes. A patent may encourage costly research by offering temporary exclusivity, but it can also raise access prices. Safety licensing may screen providers, but an unnecessarily tight quota creates artificial scarcity. Analysis should compare the benefit served by a barrier with its restriction on entry.

Durable power requires more than size

A large firm may have low prices because it is efficient, or high prices because entry is blocked. Market share alone cannot distinguish the two. Economists also examine price-cost margins, entry history, buyer alternatives, capacity, contracts, and whether customers can coordinate around a new platform.

Potential competition matters when entry is timely, likely, and sufficient. A theoretical entrant that needs ten years of construction does little to constrain today's price.

Diagnose three very different monopolies

A patented medicine is protected by law for a limited period. A social platform may be protected by network effects because a new service with few users is less useful. A water network may be protected by cost: duplicating pipes can raise total cost. Calling all three “monopoly” is only the beginning; each requires different evidence and policy.

For the patent, ask whether exclusivity encourages research and whether its duration is proportionate. For the platform, examine interoperability, data portability, and switching. For water, estimate average cost over the entire demand range. A single remedy cannot fit all three mechanisms.

Distinguish success from exclusion

A firm can become large by offering a better product, and that success can benefit consumers. Concern rises when the firm can prevent equally efficient rivals from reaching buyers or when customers cannot switch. Evidence about contracts, compatibility, control of inputs, and actual entry attempts is more informative than size alone.

Use a four-step investigation: define the market, identify the barrier, test how durable it is, and compare the barrier's possible benefit with its restriction on competition.