F An Oligopoly is characterized by a small number of interdependent firms that constitute the entire market. F By combining the market share of the top 20 companies, the concentration ratio of an Oligopoly can be established. F If Wal-Mart lowers their prices, and steals share from their competitors, it is considered a zero-sum game. A cartel agreement is not considered a form of Oligopoly. F High barriers of entry are a key component for a Monopoly to exist in the long run. F A Monopoly faces a relatively elastic demand curve; it cannot charge just any price at all. F Sales promotion and advertising is key in a Monopolistic Competitive market to create demand and differentiate the product. F Oligopolies working together in strategic behavior and game theory in the US is legal