人口老龄化、养老保险制度设计与收入不平等的动态演化

Population Ageing,Endowment Insurance System Design and Dynamic Evolution of Income Inequality

本文通过构建世代交叠模型分析人口老龄化如何影响中国养老保险制度的收入分配效应。研究发现,当生育外生时,统筹账户养老金计发办法可以激励低收入群体更多地投入子代教育,从而降低代内收入不平等;而当生育内生时,由于还存在生育“数量-质量”互替机制,代内收入不平等的演化方向变得不再清晰。当生育外生时,预期寿命延长会降低代内收入不平等但提高代际收入不平等,生育率下降会降低代内收入不平等且对代际收入不平等的影响不确定;而当生育内生时,预期寿命延长对代内和代际收入不平等的影响都是模糊的。数值模拟结果还显示,在人口老龄化冲击下,养老保险制度对总体收入分配的正向调节作用将被弱化。

This paper constructs a three-period overlapping generations model to describe how population ageing affects income inequality by influencing China’s endowment insurance system. The main findings are as follows: firstly, the method of calculating the benefits of the endowment insurance pooling account can incentivise low-income groups to invest more in education to improve the human capital of their children and thus reduce intra-generational income inequality under the exogenous fertility assumption. In addition, due to the existence of the quality and quantity trade-off mechanism, the evolutionary direction of intra-generational income inequality becomes unclear under the endogenous fertility assumption. Secondly, under the exogenous fertility assumption, increased life expectancy can reduce intra-generational income inequality and increase inter-generational income inequality, and declining fertility can reduce the intra-generational income inequality, while its impact on inter-generational income inequality is uncertain. Under the endogenous fertility assumption, the impact of increased life expectancy on intra-and inter-generational income inequality is ambiguous. Thirdly, the results of the numerical simulation show that population ageing will eventually weaken the positive adjustment effect of the endowment insurance system on the overall income distribution.