In economic theory, perfect competition (sometimes called pure competition) describes markets such that no participants are large enough to have the market power to set the price of a homogeneous product. Because the conditions for perfect competition are strict, there are few if any perfectly competitive markets. Still, buyers and sellers in some auction-type markets, say for commodities or some financial assets, may approximate the concept. As a Pareto efficient allocation of economic resources, perfect competition serves as a natural benchmark against which to contrast other market structures.


Equilibrium in perfect competition is the point where market demands will be equal to market supply. A firm’s price will be determined at this point. In the short run, equilibrium will be affected by demand. In the long run, both demand and supply of a product will affect the equilibrium in perfect competition. A firm will receive only normal profit in the long run at the equilibrium point.

Market Equilibrium and the Perfect Competition.

The remaining chapters of this text are devoted to the operations of markets. In economics, a market refers to the collective activity of buyers and sellers for a particular product or service.

In this chapter we will focus on what might be considered the gold standard of a market: the perfect competition model. The operations of actual markets deviate from the perfect competition model, sometimes substantially. Still, this model serves as both a good initial framework for describing how a market functions and a reference base for evaluating any market.

Assumptions of the Perfect Competition.

The perfect competition model is built on five assumptions:

  1. The market consists of many buyers. Any single buyer represents a very small fraction of all the purchases in a market. Due to its insignificant impact on the market, the buyer acts as a price taker, meaning the buyer presumes her purchase decision has no impact on the price charged for the good. The buyer takes the price as given and decides the amount to purchase that best serves the utility of her household.
  2. The market consists of many sellers. Any single seller represents a very small fraction of all the purchases in a market. Due to its insignificant impact on the market, the seller acts as a price taker, meaning the seller presumes its production decisions have no impact on the price charged for the good by other sellers. The seller takes the price as given and decides the amount to produce that will generate the greatest profit.
  3. Firms that sell in the market are free to either enter or exit the market. Firms that are not currently sellers in the market may enter as sellers if they find the market attractive. Firms currently selling in the market may discontinue participation as sellers if they find the market unattractive. Existing firms may also continue to participate at different production levels as conditions change.
  4. The good sold by all sellers in the market is assumed to be homogeneous. This means every seller sells the same good, or stated another way, the buyer does not care which seller he uses if all sellers charge the same price.
  5. Buyers and sellers in the market are assumed to have perfect information. Producers understand the production capabilities known to other producers in the market and have immediate access to any resources used by other sellers in producing a good. Both buyers and sellers know all the prices being charged by other sellers.
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Operation of a Perfectly Competitive Market in the Short Run

The consequence of the preceding assumptions is that all exchanges in a perfectly competitive market will quickly converge to a single price. Since the good is viewed as being of identical quality and utility, regardless of the seller, and the buyers have perfect information about seller prices, if one seller is charging less than another seller, no buyer will purchase from the higher priced seller. As a result, all sellers that elect to remain in the market will quickly settle at charging the same price.

In the case of the perfect competition model, since sellers are price takers and their presence in the market is of small consequence, the demand curve they see is a flat curve, such that they can produce and sell any quantity between zero and their production limit for the next period, but the price will remain constant.

The equilibrium market wage is W, and the equilibrium number of workers employed is Q. At wage rates greater than W, the demand for labor would be less than the supply of labor, implying that there would be a labor surplus. At wage rates below W, the demand for labor would be greater than the supply of labor, implying that there would be a labor shortage. A labor surplus is eliminated when some workers agree to sell their labor for lower wages, thereby driving down the market wage rate to W. A labor shortage is eliminated when some firms agree to employ workers at higher wages, thereby driving the market wage rate up to W. At the equilibrium wage rate, there is no surplus or shortage of labor.

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Aumann, R. J. (1964), “Markets with a Continuum of Traders”, Econometrica, Vol. 32, No. 1/2, Jan.–Apr., pp. 39–50.

Clifton, J. A. (1977), “Competition and the evolution of the capitalist mode of production”, Cambridge Journal of Economics, vol. 1, no. 2, pp. 137–151.

Frank, R., Microeconomics and Behavior 7th ed. (McGraw-Hill) ISBN 978-0-07-126349-8.

Garegnani, P. (1990), “Sraffa: classical versus marginalist analysis”, in K. Bharadwaj and B. Schefold (eds), Essays on Piero Sraffa, London: Unwin and Hyman, pp. 112–40 (reprinted 1992 by Routledge, London).

Kirzner, I. (1981), “The ‘Austrian’ perspective on the crisis”, in D. Bell and I. Kristol (eds), The Crisis in Economic Theory, New York: Basic Books, pp. 111–38.

Kreps, D. M. (1990), A Course in Microeconomic Theory, New York: Harvester Wheatsheaf.

Lee, F.S. (1998), Post-Keynesian Price Theory, Cambridge: Cambridge University Press.

McNulty, P. J. (1967), “A note on the history of perfect competition”, Journal of Political Economy, vol. 75, no. 4 pt. 1, August, pp. 395–399


Roberts, J. (1987). “Perfectly and imperfectly competitive markets”, The New Palgrave: A Dictionary of Economics, v. 3, pp. 837–41.


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