本文利用中国家庭收入调查2013年的数据，研究了我国养老保险制度的再分配效应和人群差异性的问题。研究发现，养老保险制度对全国收入差距具有改善作用，缩小了城镇内部的收入差距，但扩大了城乡间的收入差距。除此之外，养老保险在不同特征人群之间具有明显的差异性，比如高教育人群的覆盖率、缴费水平和养老金水平都比低教育人群更高。值得注意的是，养老保险缴费具有“累退性”，即收入越高，缴费比例越小。基于上述研究，本文还进行了反事实分析。首先，假设养老保险实现全覆盖并计算模拟制度的再分配效应，相比实际制度，结果并没有被优化，反而扩大了收入差距。这主要是因为养老保险缴费具有累退性，全覆盖使缴费对收入差距的反向调节作用增大。其次，假设城乡制度合并，发现模拟制度缩小了全国收入差距。这得益于养老金收入大幅缩小了农村内部和城乡之间的收入差距。

Based on the data of China Household Income Project in 2013, this paper studies the redistribution effect and population difference of China's pension insurance system. The results show that pension insurance has an improvement effect on the national income gap, while narrowing the income gap within cities. However, the income gap between urban and rural areas is widened. In addition, pension insurance has differences among people with different characteristics, such as the coverage rate, contribution and pension income of high-education people are higher than those of low-education people. It is worth noting that pension insurance contributions are "regressive", that is, the higher the income, the smaller the contribution rate. Based on the above research, counterfactual analysis is conducted in this paper. Firstly, assuming that pension insurance has achieved full coverage and the redistribution effect of the simulated system has been calculated, the redistribution effect is not improved, compared with actual system. This is mainly because the contributions are regressive, and full coverage will increase the reverse adjustment effect of contributions on the income gap. Secondly, assuming urban and rural systems are consistent, it is found that the simulation system reduces the national income gap because pension income greatly narrows the income gap not only between urban and rural areas, but also within the countryside.