Competition Among the Few
In July, 2005, General Motors Corporation (GMC) offered “employee discount pricing” to virtually all GMC customers, not just employees and their relatives. This new marketing strategy introduced by GMC obviously affected Ford, Chrysler, Toyota and other automobile and truck manufacturers; Ford matched GMC’s employee-discount plan by offering up to $1,000 to its own employees who convinced friends to purchase its cars and trucks. Ford also offered its customers the same prices paid by its employees. By mid-July, Chrysler indicated that it was looking at many alternatives, but was waiting for GMC to make its next move. Ultimately, Chrysler also offered employee discount pricing.
Toyota had to respond. It quickly developed a new marketing strategy of its own, which included lowering the prices of its cars and offering new financing terms. The responses of Ford, Chrysler, and Toyota to GMC’s pricing strategy obviously affected the outcome of that strategy. Similarly, a decision by Procter & Gamble to lower the price of Crest toothpaste may elicit a response from Colgate-Palmolive, and that response will affect the sales of Crest. In an oligopoly, the market is dominated by a few firms, each of which recognizes that its own actions will produce a response from its rivals and that those responses will affect it.
The firms that dominate an oligopoly recognize that they are interdependent: What one firm does affects each of the others. This interdependence stands in sharp contrast to the models of perfect competition and monopolistic competition, where we assume that each firm is so small that it assumes the rest of the market will, in effect, ignore what it does. A perfectly competitive firm responds to the market, not to the actions of any other firm. A monopolistically competitive firm responds to its own demand, not to the actions of specific rivals. These presumptions greatly simplify the analysis of perfect competition and monopolistic competition. We do not have that luxury in oligopoly, where the interdependence of firms is the defining characteristic of the market.
Some oligopoly industries make standardized products: steel, aluminum, wire, and industrial tools. Others make differentiated products: cigarettes, automobiles, computers, ready-to-eat breakfast cereal, and soft drinks.
Measuring Concentration in Oligopoly
Oligopoly means that a few firms dominate an industry. But how many is “a few,” and how large a share of industry output does it take to “dominate” the industry?
Compare, for example, the ready-to-eat breakfast cereal industry and the ice cream industry. The cereal market is dominated by two firms, Kellogg’s and General Mills, which together hold more than half the cereal market. This oligopoly operates in a highly concentrated market. The market for ice cream, where the four largest firms account for just less than a third of output, is much less concentrated.
One way to measure the degree to which output in an industry is concentrated among a few firms is to use a concentration ratio, which reports the percentage of output accounted for by the largest firms in an industry. The higher the concentration ratio, the more the firms in the industry take account of their rivals’ behavior. The lower the concentration ratio, the more the industry reflects the characteristics of monopolistic competition or perfect competition.
The U.S. Census Bureau, based on surveys it conducts of manufacturing firms every five years, reports concentration ratios. These surveys show concentration ratios for the largest 4, 8, 20, and 50 firms in each industry category. Some concentration ratios from the 2007 survey, the latest available, are reported in Table 11.1 “Concentration Ratios and Herfindahl–Hirschman Indexes.” Notice that the four-firm concentration ratio for breakfast cereals is 80%; for ice cream it is 53%.
Table 11.1 Concentration Ratios and Herfindahl–Hirschman Indexes
| Industry | Largest 4 firms | Largest 8 firms | Largest 20 firms | Largest 50 firms | HHI |
|---|---|---|---|---|---|
| Ice cream | 53 | 66 | 84 | 94 | 954 |
| Breakfast cereals | 80 | 92 | 100 | 100 | 2426 |
| Cigarettes | 98 | 99 | 100 | *D | |
| Men’s and boys’ shirts | 56 | 75 | 90 | 98 | 1102 |
| Women’s and girls’ blouses and shirts | 42 | 58 | 80 | 94 | 719 |
| Automobiles | 68 | 91 | 99 | 100 | 1449 |
| Sporting and athletic goods | 27 | 38 | 53 | 68 | 253 |
| Dental laboratories | 18 | 24 | 29 | 36 | 102 |
| *D, data withheld by the government to avoid revealing information about specific firms. |
Two measures of industry concentration are reported by the Census Bureau: concentration ratios and the Herfindahl–Hirschman Index (HHI). Source: Selected statistics from Sector 31: Manufacturing: Subject Series—Concentration Ratios: Share of Value of Shipments Accounted for by the 4, 8, 20, and 50 Largest Companies for Industries: 2007.
An alternative measure of concentration is found by squaring the percentage share (stated as a whole number) of each firm in an industry, then summing these squared market shares to derive a Herfindahl–Hirschman Index (HHI). The largest HHI possible is the case of monopoly, where one firm has 100% of the market; the index is 1002, or 10,000. An industry with two firms, each with 50% of total output, has an HHI of 5,000 (502 + 502). In an industry with 10,000 firms that have 0.01% of the market each, the HHI is 1. Herfindahl–Hirschman Indexes reported by the Census Bureau are also given in Table 11.1 “Concentration Ratios and Herfindahl–Hirschman Indexes.” Notice that the HHI is 2,521 for breakfast cereals and only 736 for ice cream, suggesting that the ice cream industry is more competitive than the breakfast cereal industry.
In some cases, the census data understate the degree to which a few firms dominate the market. One problem is that industry categories may be too broad to capture significant cases of industry dominance. The sporting goods industry, for example, appears to be highly competitive if we look just at measures of concentration, but markets for individual goods, such as golf clubs, running shoes, and tennis rackets, tend to be dominated by a few firms. Further, the data reflect shares of the national market. A tendency for regional domination does not show up. For example, the concrete industry appears to be highly competitive. But concrete is produced in local markets—it is too expensive to ship it very far—and many of these local markets are dominated by a handful of firms.
The census data can also overstate the degree of actual concentration. The “automobiles” category, for example, has a four-firm concentration ratio that suggests the industry is strongly dominated by four large firms (in fact, U.S. production is dominated by three: General Motors, Ford, and Chrysler). Those firms hardly account for all car sales in the United States, however, as other foreign producers have captured a large portion of the domestic market. Including those foreign competitors suggests a far less concentrated industry than the census data imply.
