St. Louis Fed, Report: What Makes a Market an Oligopoly?

“As the table shows, in addition to having only a few sellers or suppliers dominating the market, an oligopoly has barriers to entering the market, and “there are few close substitutes for the product.”

In other words, certain conditions make it difficult for potential competitors to start selling or supplying a particular product or service within that industry, and there aren’t many alternatives that could be used instead. Monopolies—markets in which one firm dominates—also have those barriers …”