The Kinked-Demand curve theory is an economic theory regarding oligopoly and monopolistic competition. This is termed monopolistic competition, whereas in oligopoly the companies interact strategically. The Hollywood oligopoly replaced the Edison monopoly. Its purpose is to prevent monopoly or oligopoly on broadcasting. The term oligopoly comes from the phrase oligarchy. In conditions of monopoly and oligopoly, the "invisible hand" fails. At this point, Marcos controlled both the oligarchy and the oligopoly. In an oligopoly, firms operate under imperfect competition. An oligopoly is when a few firms dominate a market. In oligopoly theory he developed the conjectural variation approach. This leaves the weaker airlines to merge, eliminating market choices and creating an oligopoly market. Market shares in an oligopoly are typically determined by product development and advertising. Examples are "Cournot oligopoly", and "Bertrand oligopoly for differentiated products". Planned obsolescence tends to work best when a producer has at least an oligopoly. It contrasts with an oligopoly, where there are many buyers but few sellers.