Identify three markets in the U. S. economy that are oligopolistic in nature. What's the nature of the interdependence observed in those markets, and provide an example of the strategic behavior involved.

The US consumer market is a mature market where many oligopolies exist. Economists often use the 4 firm concentration ratio or the Herfindahl-Hirschman Index to measure how oligopolistic a market is by measuring the relative sales of each of the largest firms. Based on those metrics, here are three markets in the US which could be considered oligopolistic:

1. Domestic Auto Production: In the US, the classic example of an oligopoly is automotive production. There are three large firms that dominate the domestic US automotive market which are Ford, General Motors, and Chrysler/Fiat. These firms are able to produce cars and trucks cheaper than newer firms and act in interdependent ways. They do not often engage in price competition, instead, they use non-price competition, such as feature development and advertising.
2. Soft drinks: Coke and Pepsi both hold a dominant share of the soda market in the US. While it is possible for new firms to enter the market, it would be difficult to compete with the existing firms. Advertising, supply chains, and getting the new product into stores would all be significant barriers to entry for any new firm. Further Coke and Pepsi both operate as interconnected firms that make pricing, advertising, and production decisions.
3. Credit Cards: Consumer credit markets are oligopolistic since there are only a few firms that dominate the market, which are: Visa, Mastercard, American Express, and Discover. Because of these established firms and their relationships with banks, consumers, and retailers, it is tremendously difficult for new firms to enter the market.