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chapter 12

monopolistic competition and oligopoly


Pure competition and pure monopoly are the exceptions, not the rule, in the U.S. economy. In this chapter, the two market structures that fall between the extremes are discussed. Monopolistic competition contains a considerable amount of competition mixed with a small dose of monopoly power. Oligopoly, in contrast, implies a blend of greater monopoly power and less competition.

First, monopolistic competition is defined, listing important characteristics, typical examples, and efficiency outcomes. Next we turn to oligopoly, surveying the possible courses of price, output, and advertising behavior that oligopolistic industries might follow. Finally, oligopoly is assessed as to whether it is an efficient or inefficient market structure.


There are a number of minor revisions to this chapter. The opening has been shortened and tightened in focus. Tables and the “Global Perspectives” have been updated.

The term “strategic behavior” is now integrated into the discussion to reflect its common use in the literature. A “Consider This” box on strategic behavior has been added. It appeared previously in the “Analogies, Anecdotes, and Insights” section on the website.


After completing this chapter, students should be able to

  1. List the characteristics of monopolistic competition.

  2. Explain how product differentiation occurs in similar products.

  3. Determine the profit maximizing price and output level for a monopolistic competitor in the short run when given cost and demand data.

  4. Explain why a monopolistic competitor will realize only normal profit in the long run.

  5. Identify the reasons for excess capacity in monopolistic competition.

  6. Explain how product differentiation may offset these inefficiencies.

  7. Describe the characteristics of an oligopolistic industry.

  8. Differentiate between homogeneous and differentiated oligopolies.

  9. Identify and explain the most important causes of oligopoly.

  10. Describe and compare the concentration ratio and the Herfindahl index as ways to measure market dominance in an industry.

  11. Use a profit-payoffs matrix (game theory) to explain the mutual interdependence of two rival firms and why oligopolists might tempt to cheat on a collusive agreement.

  12. Identify three possible models of oligopolistic price-output behavior.

  13. Use the kinked demand curve theory to explain why prices tend to be inflexible.

  14. Explain the major advantages of collusion for oligopolistic producers.

  15. List the obstacles to collusion behavior.

  16. Explain price leadership as a form of tacit collusion.

  17. Explain why oligopolies may prefer nonprice competition over price competition.

  18. List the positive and negative effects of advertising.

  19. Explain why some economists assert that oligopoly is less desirable than pure monopoly.

  20. Explain the three ways that the power of oligopolists may be diminished.

  21. Define and explain the terms and concepts listed at the end of the chapter.


  1. Since this chapter combines the discussion of monopolistic competition and oligopoly, there are numerous possibilities for comparison. Have students make a list of businesses with which they are familiar. Ask them to decide whether they fit best in the model of oligopoly or monopolistic competition. What characteristics were most important in making their decision? Mutual interdependence is a key concept for students to understand in this chapter. It may be the most important determinant in deciding to which market structure a particular business belongs.

  2. Obviously students need to understand how market structures differ; however, building a consistent method of evaluating a firm’s position that is the same regardless of the market structure is helpful. Refer again to the three-step process outlined in Chapter 23 (Pure Competition) to determine a firm’s situation in the short run. Using MC, ATC, and AVC consistently to determine the same information: (1) MC = MR determines the best quantity of production; (2) comparing ATC and price determines per unit profit or loss; and (3) if a loss is occurring should the firm shutdown? Compare AVC and price.

  3. Review allocative and productive efficiency and compare the long-run equilibrium outcome of pure competition with the corresponding models of monopolistic competition and oligopoly.

  4. One activity that has been used successfully in smaller classes (up to 30 students) demonstrates the difficulty in predicting outcomes where collusive behavior is possible. There are several versions of the game, but one version is as follows. Tell the class that you are prepared to auction off a $20 bill with the highest bidder taking the prize. (Warning: You need to be prepared to lose $20, so if that’s too much, use a $10 or $5 bill instead.) Each student has to submit a written bid on a scrap of paper with his or her name. Then leave the room for five minutes on some excuse while the students decide on their bids. This will give them the opportunity to “collude,” and the bright class will decide to have everyone except one person bid $.01 and the high bidder will submit $.02; then they’ll divide the spoils. The interesting part of this game is, first, to see if the class does think of colluding, and second, to see if anyone decides to cheat once the collusive agreement takes place. For example, a “cheater” could win with $.03, knowing the collusive agreement.

    Other versions of this game make it less likely that you’ll lose your whole $20. (1) Divide the class into two groups. Give one group the opportunity to talk, while you stand in the other half of the room next to the group that has been forbidden to talk. In this case you will award $10 to the high bidder in each group. The silent group will probably have bidders paying close to $10 for the $10 bill. The group with the opportunity to collude may get the $10 for $.02. (2) You could also use the original version above, but stipulate that while the winning bid will be announced, the winner’s name will not and the money will be sent to the winner. This arrangement makes it easier for someone in the group to break the agreement in order to reap the entire reward. However, that person will have to bid more than the agreed upon $.02.

    The goal of the game is to help students realize how difficult it is to predict pricing outcomes when collusive behavior is a possibility.

  1. The OPEC cartel’s changing strength is an excellent case study for demonstrating the factors that lead to successful collusive agreements and the factors that lead to their demise.

  2. The beer industry (see Last Word section) and the soft-drink industry provide other good examples of familiar industries characterized by high concentration ratios. A good research topic or class debate topic is to evaluate whether these industries have “enough” competition or if consumers would benefit from more competition. The influence of microbreweries and imports complicate analysis of the beer industry.

    7. The Wall Street Journal, Advertising Age, and Business Week, among other business periodicals, frequently have articles on industries that lend themselves to good group discussion topics. Other industries that are in the news frequently and would be suitable for discussion on whether they have become too concentrated are airlines, professional sports (any or all), college athletics, private colleges, and meatpacking.

    8. You may find the following “Concept Illustration” useful in the discussion of collusion.

Concept Illustration: Collusion
One of the most famous cases of collusion in the United States involved some very unusual methods of conspiracy. In 1960 an extensive price-fixing and market-sharing scheme involving heavy electrical equipment such as transformers, turbines, circuit breakers, and switch gear was uncovered. Such participants as General Electric, Westinghouse, and Allis-Chalmers had developed elaborate covert schemes to rig prices and divide the market. Consider switch gear equipment:
At . . . periodic meetings, a scheme or formula for quoting nearly identical prices to electric utility companies, private industrial corporations and contractors was used by defendant corporations, designated by their representatives as a “phase of the moon” or “light of the moon” formula. Through cyclic rotating positioning inherent in the formula one defendant corporation would quote the low price, others would quote intermediate prices and another would quote the high price; these positions would be periodically rotated among the defendant corporations … This formula was designed to permit each defendant corporation to know the exact price it and every other defendant corporation would quote on each prospective sale.
At these periodic meetings, a cumulative list of sealed bid business secured by all of the defendant corporations was also circulated and the representatives present would compare the relative standing of each corporation according to its agreed upon percentage of the total sales pursuant to sealed bids. The representatives present would then discuss particular future bid invitations and designate which defendant corporation should submit the lowest bid therefore, the amount of such bid, and the amounts of the bid to be submitted by others.1
1Jules Backman, The Economics of the Electrical Equipment Industry (New York: New York University Press, 1962), pp. 135-138, abridged. Reprinted by permission.


Because the term “monopolistic competition” suggests monopoly, students seem to have a difficult time recalling that monopolistic competition is the market structure closest to pure competition. Stress the word competition in the title, and perhaps draw a yardstick diagram on the board to represent the spectrum of market models from one extreme to the other. If students visually see that monopolistic competition is near to pure competition, this may help them recognize the term later. Point out that monopolistic competition is an “oxymoron”; define the term and let the students have fun thinking of others: e.g., jumbo shrimp, pretty ugly, awfully good, etc. This may help them to understand the combination term, while the market structure is competitive there is also an element of monopoly present. Alternatively, tell them that “monopolistic” is the adjective, and that “competition” is the subject.

In attempting to categorize firms into their appropriate market structure, some of the examples you might present may not fit clearly into a single market structure. Firms such as McDonald’s, Burger King, and Wendy’s behave as oligopolists in terms of their strategic behavior toward each other. Furthermore, in some markets (Interstate highway food stops), there may only be two or three fast-food restaurants. In other locations there will be numerous competitors offering a wide array of potential substitutes to consumers. If students ask whether McDonald’s is an oligopolist or monopolistic competitor, you may want to answer “yes,” and then proceed to explain (or have them identify) reasons why in some cases it will be an oligopoly firm (perhaps even a local monopoly), and other times a monopolistic competitor.


I. Review Table 23-1.

II. Monopolistic Competition: Characteristics and Occurrence

A. Monopolistic competition refers to a market situation in which a relatively large number of sellers offer similar but not identical products.

1. Each firm has a small percentage of the total market.

2. Collusion is nearly impossible with so many firms.

3. Firms act independently; the actions of one firm are ignored by the other firms in the industry.

B. Product differentiation and other types of nonprice competition give the individual firm some degree of monopoly power that the purely competitive firm does not possess.

1. Product differentiation may be physical (qualitative).

2. Services and conditions accompanying the sale of the product are important aspects of product differentiation.

3. Location is another type of differentiation.

4. Brand names and packaging lead to perceived differences.

5. Product differentiation allows producers to have some control over the prices of their products.

C. Similar to pure competition, under monopolistic competition firms can enter and exit their industries relatively easily.

D. Examples of real world industries that fit this model are found in Table 25-1.

III. Monopolistic Competition: Price and Output Determination

A. The firm’s demand curve is highly, but not perfectly, elastic. It is more elastic than the monopoly’s demand curve because the seller has many rivals producing close substitutes. It is less elastic than in pure competition, because the seller’s product is differentiated from its rivals, so the firm has some control over price.

B. In the short run situation, the firm will maximize profits or minimize losses by producing where marginal cost and marginal revenue are equal, as was true in pure competition and monopoly. The profit maximizing situation is illustrated in Figure 25-1a, and the loss minimizing situation is illustrated in Figure 25-1b.

C. In the long run situation, the firm will tend to earn a normal profit only, that is, it will break even (Figure 25-1c).

1. Firms can enter the industry easily and will if the existing firms are making an economic profit. As firms enter the industry, this decreases the demand curve facing an individual firm as buyers shift some demand to new firms; the demand curve will shift until the firm just breaks even. If the demand shifts below the break even point (including a normal profit), some firms will leave the industry in the long run.

2. If firms were making a loss in the short run, some firms will leave the industry. This will raise the demand curve facing each remaining firm as there are fewer substitutes for buyers. As this happens, each firm will see its losses disappear until it reaches the break even (normal profit) level of output and price.

3. Complicating factors are involved with this analysis.

a. Some firms may achieve a measure of differentiation that is not easily duplicated by rivals (brand names, location, etc.) and can realize economic profits even in the long run.

b. There is some restriction to entry, such as financial barriers that exist for new small businesses, so economic profits may persist for existing firms.

c. Long run below normal profits may persist, because producers like to maintain their way of life as entrepreneurs despite the low economic returns.

IV. Monopolistic Competition and Economic Efficiency

A. Review the definitions of allocative and productive efficiency.

1. Allocative efficiency occurs when price = marginal cost, i.e., where the right amount of resources are allocated to the product.

2. Productive efficiency occurs when price = minimum average total cost, i.e., where production occurs using the least-cost combination of resources.

B. Excess capacity will tend to be a feature of monopolistically competitive firms (Figure 25-2 or Figure 25-1c).

1. Price exceeds marginal cost in the long run, suggesting that society values additional units that are not being produced.

2. Firms do not produce the lowest average-total-cost level of output (Figure 25-2).

3. Average costs may also be higher than under pure competition, due to advertising and other costs involved in differentiation.

V. Monopolistic Competition: Product Variety

A. A monopolistically competitive producer may be able to postpone the long-run outcome of just normal profits through product development and improvement and advertising.

B. Compared with pure competition, this suggests some possible advantages to the consumer.

1. Developing or improving a product can provide the consumer with a diversity of choices.

2. Product differentiation is at the heart of the tradeoff between consumer choice and productive efficiency. The greater number of choices the consumer has, the greater the excess capacity problem.

C. The monopolistically competitive firm juggles three factors—product attributes, product price, and advertising—in seeking maximum profit.

1. This complex situation is not easily expressed in a simple economic model such as Figure 25-1. Each possible combination of price, product, and advertising poses a different demand and cost situation for the firm.

2. In practice, the optimal combination cannot be readily forecast but must be found by trial and error.

VI. Oligopoly: Characteristics and Occurrence

A. Oligopoly exists where a few large firms producing a homogeneous or differentiated product dominate a market.

1. There are few enough firms in the industry that they are mutually interdependent—each must consider its rivals’ reactions in response to its decisions about prices, output, and advertising.

2. Some oligopolistic industries produce standardized products (steel, zinc, copper, and cement), whereas others produce differentiated products (automobiles, detergents, and greeting cards).

B. Barriers to entry.

1. Economies of scale may exist due to technology and market share.

2. The capital investment requirement may be very large.

3. Other barriers to entry may exist, such as patents, control of raw materials, preemptive and retaliatory pricing, substantial advertising budgets, and traditional brand loyalty.

C. Although some firms have become dominant as a result of internal growth, others have gained this dominance through mergers.

D. Measuring industry concentration.

1. Concentration ratios are one way to measure market dominance. The four-firm concentration ratio gives the percentage of total industry sales accounted for by the four largest firms. The concentration ratio has several shortcomings in terms of measuring competitiveness.

a. Some markets are local rather than national, and a few firms may dominate within the regional market.

b. Interindustry competition sometimes exists, so dominance in one industry may not mean that competition from substitutes is lacking.

c. World trade has increased competition, despite high domestic concentration ratios in some industries like the auto industry.

d. Concentration ratios fail to measure accurately the distribution of power among the leading firms.

2. The Herfindahl index is another way to measure market dominance. It measures the sum of the squared market shares of each firm in the industry, so that much larger weight is given to firms with high market shares. A high Herfindahl index number indicates a high degree of concentration in one or two firms. A lower index might mean that the top four firms have rather equal shares of the market, for example, 25 percent each (25 squared x 4 = 2,500). A high index might be where one firm has 80 percent of the industry and the others have 6 percent each for a total of 6400 + (6 squared x 3) = 6,508.

3. Concentration tells us nothing about the actual market performance of various industries in terms of how vigorous the actual competition is among existing rivals.

VII. Oligopoly Behavior: A Game Theory Overview

A. Oligopoly behavior is similar to a game of strategy, such as poker, chess, or bridge. Each player’s action is interdependent with other players’ actions. Game theory can be applied to analyze oligopoly behavior. A two-firm model or duopoly will be used.

B. Figure 25-3 illustrates the profit payoffs for firms in a duopoly in an imaginary athletic-shoe industry. Pricing strategies are classified as high-priced or low-priced, and the profits in each case will depend on the rival’s pricing strategy.

C. Mutual interdependence is demonstrated by the following: RareAir’s best strategy is to have a low-price strategy if Uptown follows a high-price strategy. However, Uptown will not remain there, because it is better for Uptown to follow a low-price strategy when RareAir has a low-price strategy. Each possibility points to the interdependence of the two firms. This is a major characteristic of oligopoly.

D. Another conclusion is that oligopoly can lead to collusive behavior. In the athletic-shoe example, both firms could improve their positions if they agreed to both adopt a high-price strategy. However, such an agreement is collusion and is a violation of U.S. antitrust laws.

E. If collusion does exist, formally or informally, there is much incentive on the part of both parties to cheat and secretly break the agreement. For example, if RareAir can get Uptown to agree to a high-price strategy, then RareAir can sneak in a low-price strategy and increase its profits.

F. CONSIDER THIS … Creative Strategic Behavior

Strategic behavior can come in the form of pricing decisions, product differentiation, or through creative marketing (creating perceived product differences). It can apply to either competitive or collusive behavior (including cheating on collusive agreements).

VIII. Three oligopoly models are used to explain oligopolistic price-output behavior. (There is no single model that can portray this market structure due to the wide diversity of oligopolistic situations and mutual interdependence that makes predictions about pricing and output quantity precarious.)

A. The kinked-demand model assumes a noncollusive oligopoly. (See Key Graph 25-4.)

1. The individual firms believe that rivals will match any price cuts. Therefore, each firm views its demand as inelastic for price cuts, which means they will not want to lower prices since total revenue falls when demand is inelastic and prices are lowered.

2. With regard to raising prices, there is no reason to believe that rivals will follow suit because they may increase their market shares by not raising prices. Thus, without any prior knowledge of rivals’ plans, a firm will expect that demand will be elastic when it increases price. From the total-revenue test, we know that raising prices when demand is elastic will decrease revenue. Therefore, the noncolluding firm will not want to raise prices.

3. This analysis is one explanation of the fact that prices tend to be inflexible in oligopolistic industries.

4. Figure 25-4a illustrates the situation relative to an initial price level of P. It also shows that marginal cost has substantial ability to increase at price P before it no longer equals MR; thus, changes in marginal cost will also not tend to affect price.

5. There are criticisms of the kinked-demand theory.

a. There is no explanation of why P is the original price.

b. In the real world, oligopoly prices are often not rigid, especially in the upward direction.

B. Cartels and collusion agreements constitute another oligopoly model. (See Figure 25-5)

1. Game theory suggests that collusion is beneficial to the participating firms.

2. Collusion reduces uncertainty, increases profits, and may prohibit the entry of new rivals.

3. A cartel may reduce the chance of a price war breaking out particularly during a general business recession.

4. The kinked-demand curve’s tendency toward rigid prices may adversely affect profits if general inflationary pressures increase costs.

5. To maximize profits, the firms collude and agree to a certain price. Assuming the firms have identical cost, demand, and marginal-revenue data the result of collusion is as if the firms made up a single monopoly firm.

6. A cartel is a group of producers that creates a formal written agreement specifying how much each member will produce and charge. The Organization of Petroleum Exporting Countries (OPEC) is the most significant international cartel.

7. Cartels are illegal in the U.S., thus any collusion that exists is secret. Examples of these illegal, covert agreements include the 1993 collusion between dairy companies convicted of rigging bids for milk products sold to schools and, in 1996, American agribusiness Archer Daniels Midland, three Japanese firms, and a South Korean firm were found to have conspired to fix the worldwide price and sales volume of a livestock feed additive.

8. Tacit understandings or “gentlemen’s agreements,” often made informally, are also illegal but difficult to detect.

9. There are many obstacles to collusion.

a. Differing demand and cost conditions among firms in the industry

b. A large number of firms in the industry

c. The incentive to cheat

d. Recession and declining demand (increasing ATC)

e. The attraction of potential entry of new firms if prices are too high

f. Antitrust laws that prohibit collusion

C. Price leadership is a type of gentleman’s agreement that allows oligopolists to coordinate their prices legally; no formal agreements or clandestine meetings are involved. The practice has evolved whereby one firm, usually the largest, changes the price first and, then, the other firms follow.

1. Several price leadership tactics are practiced by the leading firm.

a. Prices are changed only when cost and demand conditions have been altered significantly and industry wide.

b. Impending price adjustments are often communicated through publications, speeches, and so forth. Publicizing the “need to raise prices” elicits a consensus among rivals.

c. The new price may be below the short-run, profit-maximizing level to discourage new entrants.

2. Price leadership in oligopoly occasionally breaks down and sometimes results in a price war. A recent example occurred in the breakfast cereal industry in which Kellogg had been the traditional price leader.

IX. Oligopoly and Advertising

A. Product development and advertising campaigns are more difficult to combat and match than lower prices.

B. Oligopolists have substantial financial resources with which to support advertising and product development.

C. Advertising can affect prices, competition, and efficiency both positively and negatively.

1. Advertising reduces a buyers’ search time and minimizes these costs.

2. By providing information about competing goods, advertising diminishes monopoly power, resulting in greater economic efficiency.

3. By facilitating the introduction of new products, advertising speeds up technological progress.

4. If advertising is successful in boosting demand, increased output may reduce long-run average total cost, enabling firms to enjoy economies of scale.

5. Not all effects of advertising are positive.

a. Much advertising is designed to manipulate rather than inform buyers.

b. When advertising either leads to increased monopoly power, or is self-canceling, economic inefficiency results.

X. The economic efficiency of an oligopolistic industry is hard to evaluate.

A. Allocative and productive efficiency are not realized because price will exceed marginal cost and, therefore, output will be less than minimum average-cost output level (Figure 25-5). Informal collusion among oligopolists may lead to price and output decisions that are similar to that of a pure monopolist while appearing to involve some competition.

B. The economic inefficiency may be lessened because

1. Foreign competition has made many oligopolistic industries much more competitive when viewed on a global scale.

2. Oligopolistic firms may keep prices lower in the short run to deter entry of new firms.

3. Over time, oligopolistic industries may foster more rapid product development and greater improvement of production techniques than would be possible if they were purely competitive. (See Chapter 26.)

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