Á lương quá cao vì khả năng thương lượng mạnh mẽ của người lao động và kết quả này trong một tỷ lệ thất nghiệp mà là ở trên mức độ hiệu quả xã hội. Tóm lại, trong mô hình của thị trường lao động mà chúng tôi đã mô tả ở đây, chúng tôi không thể làm cho một kết luận ưu tiên về hiệu quả của tỷ lệ thất nghiệp cân bằng. | COORDINATION AND EXTERNALITIES 211 1. if 1 Á firms offer an excessive number of vacancies and the equilibrium unemployment rate is below the socially optimal level 2. if 1 Á wages are excessively high because of the strong bargaining power of workers and this results in an unemployment rate that is above the socially efficient level. In sum in the model of the labor market that we have described here we cannot make a priori conclusions about the efficiency of the equilibrium unemployment rate. Given the complex externalities between the actions of firms and workers the properties of the matching function and the wage determination mechanism are crucial to determine whether the unemployment rate will be above or below the socially efficient level. APPENDIX A5 STRATEGIC INTERACTIONS AND MULTIPLIERS This appendix presents a general theoretical structure based on Cooper and John 1988 which captures the essential elements of the strategic interactions in the models discussed in this chapter. We will discuss the implications of strategic interactions in terms of the multiplicity of equilibria and analyze the welfare properties of these equilibria. Consider a number I of economic agents i 1 . I each of which chooses a value for a variable ei e 0 E which represents the agent s activity level with the objective of maximizing her own payoff a ei e i Ai where e i represents the vector of activity levels of the other agents and Ai is an exogenous parameter which influences the payoff of agent i. Payoff function ơ - satisfies the properties an 0 and aiA 0. This last assumption implies that an increase in A raises the marginal return of activity for the agent. If all other agents choose a level of activity e the payoff of agent i can be expressed as a ei e Ai V ei e . In this case the optimization problem becomes max V ei e ei from which we derive V1 e e 0 where V1 denotes the derivative of V with respect to its first argument ei. First-order condition defines the
