A quantitative analysis of the tax and social security systems in an aging Japan

随着人口迅速老龄化，日本面临着严重的公共财政问题，特别是在税收和社会保障问题方面。迫切需要进行结构改革，以适应即将到来的人口变化。我们通过生命周期一般均衡模拟模型来研究日本的税收和社会保障制度。本研究的目的是为日本老龄化社会的财政改革制定指导方针，并利用这种先进的模型技术，计算替代性税收政策对资本积累和经济福利的影响。模拟结果表明，累进支出税比累进劳动所得税刺激更多的资本积累。因此，这种新税制可能是克服日本在现行税制下面临的社会老龄化所带来的巨大福利损失的关键。我们还研究了一个理想的税收组合沿着日本现行的税收和社会保障制度的路线。研究结果表明，在收入中性条件下，提高消费税税率和降低利息税税率可能是一种理想的税收组合.我们探讨了在老龄化的日本理想的公共养老金制度。模拟结果表明，如果考虑与日本现行养老金制度规模相同的养老金制度，那么，只有基本养老金、由消费税提供资金的养老金制度，社会福利水平最高.我们调查了老龄化日本的最佳国民负担率。模拟结果表明，国民负担的最佳比率将随着日本的老龄化而上升，在人口快速老龄化时期可能超过50%。

With a population that is rapidly aging, Japan faces serious public finance problems, particularly when it comes to tax and social security issues. The structural reforms are urgently needed to accommodate the impending demographic change. We look at the Japanese tax and social security systems through a life-cycle general equilibrium simulation model. We aim to establish guidelines for fiscal reform in Japan's graying society and use such advanced modeling techniques to permit the calculation of the effects of alternative tax policies on capital accumulation and economic welfare.The following three main conclusions have been drawn.1. The simulation results show that a progressive expenditure tax stimulates much more capital accumulation than a progressive labor income tax. Thus, this new tax regime may hold the key to overcoming the large welfare loss Japan faces as its society ages under the current tax system. We also examined a desirable tax combination along the lines of the current Japanese tax and social security systems. The results suggest that an increase in the rate of tax on consumption and a decrease in the rate of tax on interest income may be a desirable tax combination under conditions of revenue neutrality.2. We explored a desirable public pension system in an aging Japan. The simulation results show that, if we consider a public pension program with the same scale as the current Japanese program, the highest level of social welfare is attained when a public pension system consists of only a basic pension and is financed by a consumption tax.3. We investigated an optimal rate of the national burden in an aging Japan. The simulation results suggest that an optimal rate for the national burden would rise as Japan ages, and may exceed 50% during a period of rapid aging of its population.