风险分散与中国混合型基本养老保险制度改革研究

本文从参保人养老投资风险分散角度研究混合型基本养老保险制度设计。通过构建一个两期消费模型,综合考虑参保人所面临的人口结构、工资增长率、养老基金投资等风险因素,本文研究了混合型基本养老保险制度中现收现付制与基金积累制的最优比例,并利用中国数据进行了测算与敏感性分析。研究发现:引入小规模个人账户基金积累制可以分散人口老龄化给现收现付制所带来的风险,中国实行混合型基本养老保险制度有其合理性;但如果要维持40%～45%的养老金替代率水平,中国基本养老保险制度的财务可持续性会面临较大挑战。

Risk Diversification and the Reform of China's Mixed Basic Pension System

China reformed its basic pension insurance system in the 1990s from a pure “pay-as-you-go” plan to a mixed system consisting of two accounts: a social pooling account operating as a pay-as-you-go plan and a personal account operating as a funded pension plan. The original intention of this reform was to achieve both fairness and efficiency in the provision of basic pensions in China. However, due to a failure to deal with the transition costs, the social pooling account accumulated large deficits. To guarantee pension payments, local governments misappropriated funds in the personal accounts, creating a large number of “empty” personal accounts. As the scale of the empty personal accounts grows, the design of the mixed basic pension system is starting to be questioned. Some scholars propose abolishing personal accounts and going back to the pure pay-as-you-go plan. Until now, the problem of empty personal pension accounts in China remains unresolved. To address this issue, we try to answer two important questions. First, what is the theoretical foundation for China's mixed basic pension insurance system？ Second, what is the optimal mix of the social pooling and personal accounts in one pension system?In the face of the population aging, many countries are considering reforms of their basic pension insurance systems. In the pension insurance literature, there are growing concerns regarding the sustainability of pay-as-you-go systems and their negative macro-economic impacts. There are also increasing worries regarding the high investment risk and redistribution restriction of funded pension systems. The two pension systems carry different risks, so there is no one clearly dominating the other. The internal return rate of the pay-as-you-go system depends on the growth rate of a country's total social wages, which depend on the quantity of labor supply and labor productivity. Although in some developed countries, the investment return rate of the funded system can be substantially higher than the internal return rate of the pay-as-you-go system,it does not necessarily indicate that the funded system is the optimal one for those countries. Doing so may overlook many other risk factors and the transition costs of pension system reform.Since a pay-as-you-go pension can be regarded as a quasi-asset, some researchers have been working on designing public pension insurance systems from the perspective of risk diversification in pension investments. In this paper, we adopt the same perspective and construct a two-period consumption utility maximization model to study the optimal split of a representative employee's pension contribution between a social pooling account and a personal pension account in the Chinese mixed pension system. When making his or her pension investment decision, the representative employee faces three types of risks related to: the total labor supply, the wage growth rate, and the pension funds' investment return rate. Based on our theoretical results, we numerically estimate the optimal ratio of the two plans in China by collecting data on the growth rate of China's basic pension insurance contribution per capita, the trend of the working-age population, and the investment return rate of the National Social Security Funds. We then perform sensitivity analysis on our results. Finally, using our optimal design for the mixed pension system, we calculate the pension contribution required to achieve a goal set by the Chinese government for the pension replacement rate.Acknowledging the significant differences in the demographic, labor productivity, and capital market in different countries, governments of all countries should carefully design their basic pension insurance system according to their specific environment and their ability to deal with risks.The optimal mix of the social pooling account and the personal account in China is determined by its own characteristics of the internal return rate of the pay-as-you-go plan and the investment return rate of the funded account. At the current stage, we find that the pay-as-you-go plan should play the dominant role in China's basic pension insurance system, but inclusion of a small-scale personal account can diversify the risks that the population aging brings to the pay-as-you-go plan. Given China's goal of achieving a pension replacement rate of between 40% to 45%, keeping its basic pension system financially sustainable will be challenging. We suggest that the Chinese government pay more attention to the long-term investment of its pension funds and adopt various family supporting policies to establish a child-friendly society and thereby increase the population's fertility rate. Furthermore, the Chinese government could consider some specific parametric adjustments to the pension insurance system, such as extending the retirement age, to better align the assets and liabilities in the pension insurance balance sheet.