If the four-firm concentration ratio of an industry is 75%, what does it mean?
Industry A is composed of five large firms and 100 small firms. The market shares of the five largest firms are, respectively, 30, 25, 20, 15, and 10. The 100 small firms together have the remaining market share. Calculate the Herfindahl-Hirshman index and determine what degree of concentration it exhibits. Would it be considered an oligopoly?