The four market structures compared

What separates the four market structures?

Five features: how many sellers there are, how different their products are, how hard it is to enter the market, how much control each firm has over its price, and how much firms compete on things other than price. Perfect competition sits at one end, with many identical sellers and no pricing power. At the other end is monopoly , a single seller with no close substitute.

Market structuresordered by how much pricing power each firm has

• Perfect competition Memorize many sellers, identical product, price takers
• Monopolistic competition Memorize many sellers, differentiated products, low barriers
• Oligopoly Memorize few interdependent sellers, high barriers
• Monopoly Memorize one seller, no close substitute, very high barriers

	Perfect competition	Monopolistic competition	Oligopoly	Monopoly
Number of sellers	Many	Many	Few	One
Product	Identical	Differentiated	Identical or differentiated	Unique, no close substitute
Barriers to entry	Very low	Low	High	Very high
Pricing power	None (price taker)	Some	Some to considerable	Considerable
Non-price competition	None	Advertising, branding	Advertising, branding	Advertising
Demand curve facing the firm	Horizontal (P = marginal revenue, MR)	Downward sloping	Downward, interdependent	The market demand curve
Long-run economic profit	Zero	Zero	Possible	Possible (if unregulated)
Well-defined supply curve	Yes (the marginal cost, MC, curve above average variable cost, AVC)	No	No	No

A price taker must accept the market price, because its output is too small to move it. Under monopolistic competition there are many firms, each selling a slightly different product, so each has a little pricing power. An oligopoly has only a few firms, so each one’s price depends on how its rivals respond.

Barriers to entry are anything that keeps newcomers out: large capital costs, patents, licenses, control of a key input, strong brands. Non-price competition means competing through quality, features, branding, advertising and service rather than a lower price. Perfect competition has none, because the products are identical.

Exam tip Count the sellers, check the product, ask how easy it is to get in.

How do you spot the structure in a scenario?

Use it

Use a three-question routine: how many sellers really set the price, can buyers tell the products apart and pay for the difference, and could a newcomer enter easily?

Which structure is this market?

• How many sellers really set the price? Use it many, few or one
• Can buyers tell the products apart, and pay for the difference? Use it identical, differentiated or unique
• Could a newcomer enter easily? Use it easy entry pulls behavior towards competition

Four scenarios to anchor the pattern:

• Wheat farmers selling into a commodity exchange. Thousands of sellers, identical product, free entry: perfect competition.
• Neighborhood hair salons. Many sellers, each with its own style, location and loyal customers, and a new salon is cheap to open: monopolistic competition.
• Three cement makers serving one region. Few sellers, an identical product, and a plant costs a fortune: oligopoly.
• The only licensed water utility in a city. One seller, no substitute, and the license blocks entry: monopoly (and usually regulated).

Appearance and behavior can differ. Three small firms making an easy-to-copy product with no brands or patents behave much like perfect competition, because the threat of entry is credible. A tight cartel of many firms can behave like a single monopolist. The structure that matters is the one that describes how firms actually set prices.

Who prefers which structure?

Owners prefer more pricing power, because it supports higher prices and profits. Buyers prefer more competition, which brings lower prices and more output. Structures with pricing power can fund research and product variety, though, so less than perfect competition is not always worse for consumers.

For an analyst, market structure drives how long a firm’s profits can last. A firm with high barriers can hold returns above its cost of capital for years. A firm in a crowded market with easy entry cannot. Porter’s five forces in Equity builds on the same features.

Go deeper Markets are defined by geography and substitutes

Ready-mix concrete is delivered within an hour of the plant, so each city is its own market, perhaps with only two or three sellers. A search engine competes globally. The same product can be an oligopoly in one definition of the market and a competitive market in another, which is why every concentration number in the next lessons depends on how the market is drawn.

Go deeper Regulated monopolies

A natural monopoly, such as a water network, has costs that fall as it serves more customers, so one firm serves the market at the lowest cost. Regulators typically cap its prices so that it earns a normal return rather than a monopoly profit. Monopoly pricing and regulation are not examined beyond the characteristics above.

Go deeper Porter's five forces and market structure

Rivalry among existing firms, the threat of new entrants and the threat of substitutes map directly onto the number of sellers, barriers to entry and the closeness of substitutes. The bargaining power of suppliers and of buyers are the two forces with no direct counterpart in the five features here. You will meet the full framework in industry analysis in Equity.