Imperfect competition

• 1. Introduction

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  Imperfect competition describes a market that fails to satisfy every condition of a perfectly competitive one. That shortfall produces market inefficiencies, and those inefficiencies can harden into outright market failure. The behavior in question usually belongs to sellers. Their rivalry with each other sits below what a perfectly competitive market would produce. Economists link a market's competitive structure, the behavior it produces, and the financial performance that follows into a single causal chain. They call it the structure-conduct-performance paradigm. To trace that chain, they measure the concentration of suppliers in a market, since concentration reveals how competitive that market really is. What concentration measures, in the end, is market power: a firm's ability to push the price of a good above its marginal cost, abbreviated MC. The further a price climbs above marginal cost, the deeper the resulting inefficiency runs. Every market sits somewhere on a spectrum running from perfect competition at one end to pure monopoly at the other. Monopoly sits at the end with the greatest power to push price above marginal cost. What actually separates these two ends of that spectrum? Why does a market's demand curve bend the way it does? And why do economists still argue over whether policy should follow the perfect model or the imperfect one? Those questions frame everything that follows.

• 2. Demand Curves

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  A downward-sloping demand curve marks every imperfectly competitive market, unlike the perfectly elastic curve found under perfect competition. Product differentiation and substitution explain that slope. A buyer can switch sellers with little effort, which keeps buyers sensitive to price. The law of demand governs the relationship: as a product's price rises, the quantity buyers demand for it falls. Whether a market crosses fully into imperfect territory turns on a specific set of conditions. Those are the same conditions economists use to define perfect competition in the first place.

• 3. Drawing The Competitive Line

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  Economists rely on a set of assumptions to define a perfectly competitive market. They use those same assumptions to build economic policy around welfare and efficiency. Under those assumptions, sellers act as price takers rather than price makers. Supply and demand push price to equal marginal cost through Pareto Efficiency and the mechanism known as the Invisible Hand. A large number of sellers keeps any single firm from holding significant market power. Barriers to entering or leaving the market stay minimal or nonexistent, and buyers and sellers hold full information. Search costs stay negligible, and the products on offer are homogeneous and divisible. Collusion between firms is absent, and so are externalities such as increasing returns to scale.

  A market earns the label imperfectly competitive the moment even one of those assumptions breaks down. Economists apply a second, sharper test on top of that: if any one of five specific conditions holds, the market counts as imperfect. Firms that are not price takers, and instead control their own pricing, meet that test. So does a market supplied by a single seller or none at all. Barriers to entering or exiting the market qualify too, along with information asymmetry between buyers and sellers. So do goods or services that are heterogeneous or differentiated rather than uniform. Those five triggers matter well beyond an economics classroom. They shape how far governments should step in once a market falls short of the perfectly competitive ideal.

• 4. The Policy Divide

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  Imperfect conditions theorists argue that no market in the aggregate economy has ever met, or ever will meet, the full conditions of perfect competition. In their view, imperfect competition is built into the structure of capitalist economies. Firms chase profit by pursuing whichever competitive strategy earns the greatest revenue. That means setting price above marginal cost even at a cost to the wider economy's efficiency. Monopoly represents the most extreme version of that trade-off: producers overcharge for what they sell and underproduce it relative to a competitive market. The resulting pricing strategies shape what consumers choose to buy, how businesses operate and earn revenue, and how policymakers write economic rules.

  Economists disagree over which assumption should guide policy, perfect competition or imperfect competition. Those who favor the imperfect view argue that policy built on perfect-competition assumptions fails, since no market ever meets purely perfectly competitive conditions. Even so, the perfect-competition approach still dominates policymaking. Its logic is widely used, and economists still lack a substantial, consistent body of imperfectly competitive models to replace it.

  Foreign trade policy shows what that theoretical divide looks like in practice. Under perfect-competition assumptions, foreign trade policy favors minimal government intervention, and subsidies count as harmful. Improving a country's terms of trade becomes the first response to import protections. Imperfect-competition assumptions push the opposite way, favoring intervention in international trade. That approach lets economists model policies that rein in an imperfectly competitive firm's market power. It can also justify building up a monopoly's power when doing so serves the national interest. Either way, the choice between these two assumptions carries consequences for policy decisions at home and abroad. Which of those two worlds a market resembles most closely depends on how many sellers compete within it, a question with four distinct answers.

• 5. Monopolistic Competition And Oligopoly

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  Four broad market structures produce imperfect competition: monopolistic competition, oligopoly, duopoly, and monopoly. Monopolistic competition seats many buyers alongside many sellers, each offering products with only some differentiation and only some control over price. Many firms compete here by selling products that are highly substitutable but never quite identical. Each seller assumes that a small change in its own price will not move the overall market price. Each also assumes rivals will not react to that change either. Products in this market are non-homogeneous, giving companies some control over price while consumers choose according to their own subjective judgment.

  Two forms of differentiation exist here. Vertical differentiation ranks a product as objectively better or worse than a rival, for instance by efficiency. Customers then compare products on objective measures like price and quality. Horizontal differentiation instead splits consumers by preference alone, as with Mercedes Benz and BMW, where taste and location, not objective quality, drive the choice. A firm entering this market may see profit rise or fall in the short term, though normal profit is what survives in the long run. If price climbs high enough above marginal cost to cover fixed costs, new firms enter and undercut price until economic profit reaches zero. Each firm holds only a small slice of the total market. Its demand curve slopes downward rather than sitting flat, unlike under perfect competition. That gap between price and marginal cost, the paradox of excess capacity, is what separates monopolistic competition from the perfectly competitive ideal.

  Oligopoly narrows that field of sellers even further, to a small number, more than two, whose decisions ripple directly into each other's businesses. A change in one oligopolist's output or price shifts the supply and pricing of the entire market. Oligopolies lean on non-price weapons instead, using advertising or changes to product features rather than price cuts, which they treat as a dangerous strategy. Several large companies typically hold large shares of an industry's output, each facing its own downward-sloping demand, in a market marked by heavy non-price competition. Businesses in this position depend on one another, and products may or may not be differentiated. Barriers to entry can be natural, cost-based, tied to market size, or deliberately dissuasive. In oligopoly those barriers run high: patents, technology, economies of scale, government regulation such as restricted licensing, and firm-name recognition. A market can narrow further still, down to just two sellers, or all the way down to one.

• 6. Duopoly And Monopoly

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  Duopoly restricts a market to exactly two sellers, a special case of oligopoly in which both firms hold exclusive power over that market. Both companies produce the same type of product, and no other company produces anything comparable. Those goods circulate in a single market that no outside company intends to enter, leaving the two firms with substantial control over price. Positioned between monopoly and perfect competition, duopoly counts as the most basic form of oligopoly.

  Monopoly reduces the field to a single supplier facing many buyers, a firm with no competitors in its industry. When competition exists at all, it comes from marginal companies that generally hold only 30 to 40 percent of the market between them. That share is too small to materially affect the monopolist's profits. A monopolist holds real market power, able to influence the price of its own good. It is the sole provider of a good or service and faces no competition in its own output market. Significant barriers, including patents, market size, and control of raw materials, keep that position secure. Public utilities such as water and electricity, and Australia Post, serve as examples of monopolies in practice.

  A monopolist's demand curve also slopes downward, so raising the price still costs it units sold, even without rivals to react to. What separates a monopolist from firms in other market models is that it sets price without weighing any competitor's strategic response. Its profit-maximizing quantity sits at the point where marginal cost equals marginal revenue. At that point, output falls below what a perfectly competitive market would produce, and price sits above marginal cost. A firm counts as a monopsonist if it is the sole buyer in a market. A natural monopoly arises whenever it is cheaper for one firm alone to supply a market's entire output. Governments often rein in monopolies through high taxes or anti-monopoly laws, reasoning that a monopolist's high profits can harm consumers. Yet restricting those profits can also hurt consumers. Companies may otherwise withhold new products that would have delivered real benefits to consumers and real economic value to the makers themselves. Tax and antitrust rules can end up discouraging innovation altogether. How tightly a handful of firms can grip a market like this can actually be measured, and one index does exactly that.

• 7. Measuring Market Concentration

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  The Herfindahl Index measures exactly how concentrated a market's firms are, by summing the squared market share of every firm in that market. Large companies count for more in this index than they would under a simple concentration ratio based only on firm numbers. Its value ranges from 1 divided by the number of firms, N, up to 1, so a higher score marks a more concentrated market. Below an index value of 0.20 sit both perfect competition, where price competition stays fierce, and monopolistic competition. There, price competition runs light or fierce depending on how differentiated its products are. Between 0.20 and 0.60 sits oligopoly, where price competition again runs light or fierce depending on how rivals interact. Above 0.60 sits monopoly, where price competition turns light or nonexistent. The four broad structures scored on this index all trace back to one deeper concept: market power itself, and where it actually comes from.

• 8. Sources Of Market Power

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  Any market whose demand curve slopes downward holds market power, meaning it has some ability to set its own price rather than simply accept one. That power lets a firm choose its price, though the demand curve still decides how much quantity buyers will take at that price. A firm should expect quantity demanded to fall if it raises that price. Four factors create this kind of power.

  Control over an important input is one: the company that runs the operations of Sydney Harbour, in Sydney, holds market power for exactly that reason. Copyrights and patents are another, especially in the health industry. Governments issue patents on major drugs so a single company becomes that drug's only legal seller. Network economies form a third source. A product's value rises as more people use it, a dynamic that boosted Instagram's popularity as more consumers began using it. That kind of effect often creates a monopoly in the product's own market. A government license is the fourth source. Yosemite Hospitality holds a United States government license to run a lodge inside Yosemite National Park. That license was granted so the government could preserve the park, though it also created a monopoly there. That license shows how a government meant to protect a park can end up handing one company control over who stays there.