Monopolistic competition

Most everyday markets, restaurants, clothing, local shops, are neither monopolies nor perfectly competitive. They are crowded with rivals selling things that are similar but not the same. That is monopolistic competition.

Monopolistic competition is a market structure with many firms selling differentiated but broadly substitutable products, with relatively free entry and exit. It blends features of competition, many firms and easy entry, with a feature of monopoly, that each firm has some power over its own price because its product is distinctive.

Differentiation gives a little power

The key to monopolistic competition is product differentiation. Each firm sells something slightly different, in quality, style, brand, location, or service, so it is not a perfect substitute for its rivals. This gives each firm a small degree of pricing power: it can raise its price a little without losing all its customers, because some prefer its particular offering. But the power is limited, since close substitutes abound, so the firm faces a downward-sloping but elastic demand curve, more freedom than a perfect competitor, far less than a monopolist.

Entry erodes profit

Like perfect competition, monopolistic competition features relatively free entry, and this drives long-run profits toward normal levels. If firms in the market are earning good profits, new firms enter with their own differentiated offerings, dividing the market more finely and competing away the excess profit, until each firm earns only a normal return. So although each firm has some pricing power, the freedom of entry prevents that power from yielding lasting monopoly profits, an important difference from true monopoly.

Efficiency and variety

Monopolistic competition is less efficient than perfect competition in narrow terms: firms produce somewhat below the lowest-cost scale and price somewhat above marginal cost, a modest deadweight loss. But it delivers something perfect competition does not, variety. The differentiation that gives firms their pricing power also gives consumers a wide choice of distinct products suited to different tastes. Whether the value of that variety outweighs the small efficiency cost is a genuine trade-off, and one reason economists do not simply condemn the structure.

Monopolistic competition describes a vast swathe of real markets, those many industries of numerous firms offering similar but distinguishable products. It captures the everyday reality that most firms have a little pricing power from being distinctive, and a lot of competitive pressure from the many rivals offering close alternatives, with the freedom of entry keeping profits in check.