Abstract: As a tool of adjusting income distribution and optimizing resources allocation, The marginal tax rate of the personal income tax has attracted extensive attention. Thereinto, the current highest marginal tax rate of 45% has sparked great controversy. This paper, in the light of China's reform of the personal income tax, uses the optimal non-linear income tax theory of Saez to calculate and analyze the highest marginal tax rate and its influencing factors in terms of different income distributions and social welfare functions, with family as its tax unit, annual income the study object and salary the example. It suggests that there is certain room for lowering the current rate of 45% as the highest marginal tax rate to strike a balance between efficiency and equity. Saez's idea is generic and provides references to the establishment of China's personal income tax system that unifies synthesis and classification.

Key words: Personal Income Tax, Highest Marginal Tax Rate, Optimal Non-linear Income Tax

摘要： 个人所得税作为调节收入分配与优化资源配置的工具,其边际税率的设定备受关注,现行45%的最高边际税率更是争议颇多。本文结合我国个人所得税改革方向,运用赛斯的最优非线性所得税理论,以家庭为纳税单位,以年收入为研究对象,以工资、薪金为例,计算和分析不同收入分布情况、不同社会福利函数的个人所得税最高边际税率及其影响因素,认为兼顾效率和公平的社会分配目标下现行45%的最高边际税率存在下调空间。赛斯的思路具有通用性,对我国建立分类与综合相结合的个人所得税制具有一定的参考意义。

关键词: 个人所得税, 最高边际税率, 最优非线性所得税