Abstract:  Theoretical studies generally show that as a financing pattern of endowment insurance, the funded system is superior to the payasyougo system from the perspective of capital per capita. This article analyzes whether the funded system is completely superior to the payasyougo system from the perspective of welfare economics with exogenous and endogenous fertilities. The theoretical model shows that: under a certain combination of parameters, either with exogenous fertility or endogenous fertility, there exists a contribution rate of pension that the social welfare under payasyougo system is higher than that under funded system. The numerical simulation shows that: the contribution rate of pension can make the social welfare under the payasyougo system higher. And in the case of exogenous fertility (which is in line with Chinas fertility policy), the social welfare is the highest when the contribution rate of payasyougo pension is around 12%; in the case of endogenous fertility (which is in line with developed countries fertility policy), the social welfare is the highest when the contribution rate of payasyougo pension is around 6%. The former value is similar to the existing research conclusions that Chinas contribution rate of payasyougo pension should be reduced to around 15%, and the latter value is similar to the current contribution rate of payasyougo pension in developed countries such as the United States (6.2%) and Japan (7.7%). The robustness test shows that: the conclusions of the numerical simulation remain as long as the parameter assignment is within a reasonable range. This paper provides theoretical support for the reduction of Chinas contribution rate of payasyougo pension.

Key words: payasyougo system, funded system, contribution rate of pension, social welfare, OLG model

摘要： 理论研究普遍认为，基金制养老保险筹资模式优于现收现付制，但这几乎都是基于人均资本视角的判断。本文在外生和内生生育率两种情形下，从福利经济学视角分析基金制是否完全优于现收现付制。理论模型表明，在一定参数组合下，无论外生生育率还是内生生育率，都存在使现收现付制下社会福利高于基金制下社会福利的养老保险缴费率。模型的数值模拟显示，存在使现收现付制下社会福利更高的养老保险缴费率，且在外生生育率下（符合我国生育政策）现收现付制缴费率在12%左右社会福利最高，内生生育率下（符合发达国家生育政策）现收现付制缴费率在6%左右社会福利最高。前一数值与已有研究成果观点相近(我国社会统筹部分缴费率应下降到15%左右)，后一数值与美国（62%）、日本（77%）等发达国家现收现付制养老保险缴费率相近。稳健性检验显示，只要参数赋值在合理范围内，数值模拟主要结论不变。本文为降低现行我国社会统筹部分养老保险缴费率提供了理论借鉴。

关键词: 现收现付制, 基金制, 养老金缴费率, 社会福利, OLG模型