3.1.5.1 - The spectrum of market structures

The competition spectrum

A market structure describes the conditions in which firms compete. It helps explain how much influence a seller has over price and how rivals or newcomers constrain its decisions. First define the market: the product and geographical area in which buyers can realistically switch supplier. One bakery may be the only shop in a village while still competing with nearby supermarkets and home delivery.

Perfect competition is the theoretical end of the spectrum with many small suppliers selling identical products, free entry and exit, and perfect knowledge. Each firm accepts the market price. Pure monopoly is the opposite end: one supplier in the defined market, protected from entry, with no close substitute. The monopolist has price-setting power, although buyers' demand still limits what it can sell.

Between these endpoints, monopolistic competition has many sellers with differentiated products and relatively easy entry. Oligopoly has a few dominant suppliers whose decisions depend strongly on their rivals' responses. The number of tiny firms outside the dominant group need not be zero. Market power means some ability to influence price; it is not a promise of unlimited profit.

The models are benchmarks. A real market need not fit every assumption in one row. Oligopoly is especially varied: a homogeneous industrial material and strongly branded consumer products may both be supplied by a few dominant firms.

What changes competitive pressure

Competition depends on the strength of alternatives available to customers and potential entrants, rather than on the firm count alone.

With many small suppliers, losing one customer has little effect on total market supply; a firm charging more for an identical product can lose customers to others. With fewer large suppliers, one firm's output or price change can materially affect rivals' sales. This makes strategic reactions more important. Still, two vigorous rivals can compete intensely, so concentration alone does not prove weak competition.

Product differentiation makes a product distinct in buyers' eyes through features, quality, design, location, service or branding. A preferred café can raise its price slightly without losing every customer because its offer is not identical to its neighbours'. The closer the substitutes and the easier switching is, the more elastic its demand tends to be and the less price power it has. Advertising may communicate a real difference or create perceived loyalty.