What it means
Economics textbooks start with perfect competition, a tidy model in which many small firms sell identical products, everybody knows every price and no single seller can shift the market. That model is a useful benchmark, but virtually no real market meets its conditions.
Imperfect competition is the umbrella term for everything else. It includes monopoly, where one firm supplies the market, oligopoly, where a handful of large firms watch each other closely, and monopolistic competition, where many firms sell products that customers see as meaningfully different.
What links these structures is pricing power. Because customers cannot switch instantly to an identical substitute, a firm can raise price somewhat without losing all its sales, which means it faces a downward sloping demand curve rather than a flat one.
That single fact changes how the firm should think about price, volume and investment. For managers this is not an abstraction, it is the whole basis of strategy.
Brands, patents, network effects, switching costs, distribution control and location are all ways of creating or defending the imperfection that lets a firm earn more than a bare return on capital. The measurement most often used is the Lerner Index, the gap between price and marginal cost expressed as a share of price.
It runs from zero under perfect competition to close to one where a seller faces almost no competitive constraint, and competition authorities use similar reasoning when assessing mergers and market dominance.
In practice
Real-world examples.
Example
Two supermarket chains dominate a small country and each monitors the other's weekly promotions closely. Neither cuts headline prices deeply, because both know a price war would be matched within days and simply shrink margins across the whole sector.
Example
A coffee roaster in a city with dozens of independent cafes charges 15% more than the shop across the street and still fills its seats. Its customers value the roast, the room and the staff, which is monopolistic competition in action: many sellers, but each one slightly different.
Example
A pharmaceutical company holds a patent on a treatment with no close alternative and prices it far above manufacturing cost. When the patent expires and three generic makers enter, the price falls sharply because the imperfection that supported it has gone.
Formula
Calculation
Pricing power is measured by the Lerner Index: L = (Price - Marginal Cost) / Price. It links to demand through the optimal pricing rule: Price = Marginal Cost / (1 - 1/elasticity), where elasticity is the absolute value of price elasticity of demand.
A specialist laboratory equipment maker sells an analyser for $80 per unit, and the marginal cost of producing one more unit is $48.
Lerner Index = ($80 - $48) / $80 = $32 / $80 = 0.40.
A value of 0.40 says that 40% of the price is margin over marginal cost, which would be impossible under perfect competition where price equals marginal cost.
Working backwards through the pricing rule, the implied elasticity is 2.5, because $48 / (1 - 1/2.5) = $48 / 0.6 = $80. In words, a 1% price rise costs the firm about 2.5% of unit sales.
At 50,000 units a year, total contribution = 50,000 x $32 = $1,600,000. If a rival launched a close substitute and elasticity rose to 4, the optimal price would fall to $48 / (1 - 0.25) = $64, cutting contribution per unit to $16 and reducing the Lerner Index to 0.25.Case study
Seen in the real world.
The following scenario is illustrative and the firm is fictional. Northbeck Fasteners, an invented industrial supplier, made specialist bolts for wind turbine manufacturers and long behaved as though it sold a commodity, quoting near cost to win tenders and earning thin single-digit margins.
A new commercial director in this fictional account ran a simple analysis and found that Northbeck's parts were certified to a standard only two other suppliers held, that re-certifying an alternative supplier took a customer roughly nine months, and that the bolts represented under 2% of a turbine's cost. Those three facts described a market that was far from perfectly competitive, yet Northbeck had been pricing as if it were.
The illustrative change was modest and deliberate. Northbeck raised prices by 9% on certified lines only, held prices on genuinely commoditised stock items, and invested the extra margin in shortening lead times. Volume fell by about 3%, contribution rose materially, and the fictional post-mortem concluded the firm had been giving away pricing power it had spent a decade earning.
Watch out
Common mistakes.
- Treating imperfect competition as a market failure that must be corrected, when some imperfection is the normal reward for investment in brands, research and quality.
- Assuming pricing power means charging whatever you like, when demand still slopes downward and every price rise costs volume.
- Confusing a high margin with abuse of market power, when high margins can equally reflect low marginal costs, heavy fixed investment or genuinely better products.
Questions
People also ask.
Is imperfect competition bad for customers?
Not necessarily, because the same conditions that allow higher prices also fund product development, variety and service that a purely commoditised market would not support.
What is the difference between oligopoly and monopolistic competition?
Oligopoly has a few large firms whose decisions directly affect each other, while monopolistic competition has many firms that differentiate their offering but are too small to influence rivals individually.
How do competition regulators decide when to intervene?
They look at market share, barriers to entry, the ease of switching and evidence of coordinated or exclusionary behaviour, rather than at profitability alone.
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