微观经济学16寡头垄断.ppt

Figure 1 The Four Types of Market Structure Figure 2 The Prisoners’ Dilemma Figure 3 An Oligopoly Game Figure 4 An Arms-Race Game Figure 5 An Advertising Game Figure 6 A Common-Resource Game Figure 7 Jack and Jill Oligopoly Game Appendix: Ignoring Interdependencies: The Cournot Oligopoly Models vary depending on assumptions of actions of rivals to pricing and output decisions. Augustin Cournot (1838) created a model that is the basis of Anti-trust Policy in the US. Relatively simple assumption: ignore the interdependency with rivals This makes the math easy A Numerical Example:Competition, Monopoly, and Cournot Oligopoly IN COMPETITION P = MC, so 950 - Q = 50 PC = $50 and QM = 900 IN MONOPOLY MR = MC, so 950 -2Q = 50 QM = 450 so PM = 950 - 450 = $500 IN DUOPOLY Let Q = q1 + q2 Cournot Solution: Case of 2 Firms (Duopoly) Assume each firm maximizes profit Assume each firm believes the other will NOT change output as they change output. The so-called: Cournot Assumption Find where each firm sets MR = MC Let Q = q1 + q2 With 2 Equations 2 Unknowns: Solve for Output 950 -2q1 - q2 = 950 - q1 - 2q2 So, q2 = q1 Then plug this into the demand equation we find: 950 - 2q1 - q1 = 950 - 3q1 = 50. Therefore q1 = 300 and Q = 600 The price is: P = 950 - 600 = $350 N-Firm Cournot Model For 3 firms with linear demand and cost functions: Q = q 1 + q 2 + q 3 In linear demand and cost models, the solution is higher output and lower price QCournot = { N / (N+1) }QCompetition Example: Cournot as N Increases If N = 3 Triopoly P = 950 - Q MC=50 Then, Q = (3/4)(900) Q = 675 P =$275 If N = 5 P = 950 - Q and MC = 50 Then Q = (5/6)(900) Q = 750 P = $200 Appendix: Collusion versus Competition? Sometimes collusion succeeds Sometimes forces of competition win out over collective action When will collusion tend to succeed? There are six factors that influence successful collusion as follows: Factors Affecting Likelihood of Successful Collusion 1. Number and Size Distr