理论基尼系数及其社会福利含义的讨论

The Theoretical Gini Coefficient and its Implication about Social Welfare

尽管关于基尼系数的经验估计与研究异常丰富,但是对于基尼系数的理论含义一直缺乏严格的推导。本文试图从收入分布函数的定义出发,严格探讨基尼系数的理论含义和性质,以澄清一些关于基尼系数的误解。本文认为,最优的基尼系数值不可能从基尼系数的定义本身找到答案,必然牵涉到关于社会福利的价值判断。此外,一旦得到具体的收入分布函数,基尼系数的计算可以通过分布函数的参数估计来实现,因此本文最后给出了产生收入分布函数以及计算基尼系数的一种简单法则。

Although the empirical researches about the Gini coefficient are extraordinarily plentiful,the formal theoretical deduction of the Gini coefficient is usually omitted.This paper attempts to formally explore the theoretical definition and properties of the Gini coefficient under continuous income distribution in order to clear up some misunderstanding about the Gini coefficient.The optimal value of Gini coefficient will necessarily be concerned with the value judgment of the social welfare and thus cannot be obtained from the definition of Gini coefficient itself.In addition,given the specific income distribution function,the calculation of the Gini coefficient can be realized by the parameter estimation about the income distribution function.A simple rule for generating income distribution function and calculating the Gini coefficient is proposed in the final section.