为什么完全竞争市场最终会导致垄断?

Why the Competitive Market will Lead to Monopoly?

借助随机增长模型,探讨完全竞争市场下市场集中的可能性。假设企业在初始阶段完全一致,不存在外部性、信息不对称等。企业规模由企业技术水平内生决定,所有企业技术水平受到的冲击都为独立同分布。发现:(1)假设企业数量为连续统。如果没有运营成本,稳态的企业规模分布满足齐普夫法则,呈现长尾分布的形式;如果存在运营成本,没有新的企业进入,较低水平的企业会陆续退出,市场会逐渐集中;(2)如果企业数量有限,行业可能会被一个企业垄断。数值模拟和经验证据支持了结论。

This paper employs the random growth model to discuss the possibility of market concentration under a perfectly competitive market.Assuming that the enterprise is completely consistent in the initial stage,and there is no externality or asymmetric information.The scale of an enterprise is determined endogenously by its technological level,and all the shocks to its technological level are distributed independently and identically.The research finds that:(1)Assuming the firm number is continuum.If there is no entry cost,the stationary distribution of the firm size satisfies the Zipf’s Law,which takes the form of a long tail distribution.If there exists some fixed cost and no new enter into the market,the firms having low technology would exit the market and the market will be in concentration.(2)If the firm number is finite,the market will be in monopoly.The numerical simulations and empirical evidence support the conclusion.