资本价值与宏观投资率:应用包含调整成本的拉姆齐模型的研究

Capital Value and Macro Investment Rate:Application of the Ramsey Model Including Adjustment Cost

学术界对中国宏观投资率是否过高存在争议。应用包含调整成本的拉姆齐模型,从理论上分析资本价值影响宏观投资率的机制:中低收入经济体人均资本存量相对较低,资本边际产出较高,由此推断资本边际价值较高,从而推高了宏观投资率;随着该经济体人均资本存量的提高,其资本边际价值会逐渐降低至发达经济体水平,在此收敛过程中宏观投资率也会逐渐下降。在企业价值最大化时,资本边际价值等于购买价格与边际调整成本之和,其中边际调整成本是资本边际价值的关键组成部分。逆向积分数值模拟测算结果表明,2000—2019年,中国考虑调整成本的福利最大化宏观投资率比忽略调整成本时平均高8.78个百分点,两者在统计上存在显著性差异,说明调整成本对宏观投资率具有显著影响,即高资本边际价值引致高宏观投资率。进一步分析发现,在考虑调整成本的情况下,中国福利最大化宏观投资率高于实际的宏观投资率,说明中国宏观投资率未必过高。

There is controversy about whether China s macro investment rate is too high.In this paper,the mechanism of capital value influencing macro investment rate is theoretically constructed by using Ramsey model including adjustment cost:Low-and middle-income economies have relatively low capital stock per capita,high marginal product of capital and high marginal value of capital,thus pushing up the macro investment rate.As the per capita capital stock of the economy increases,the marginal value of capital will gradually decrease to the level of developed economies,and the macro investment rate will also gradually decline in the process of convergence.When firm value is maximized,the marginal value of capital is equal to the sum of purchase price and the marginal adjustment cost.Among them,marginal adjustment cost is the key component of capital marginal value.The reverse integral numerical simulation results show that,from 2000 to 2019,China s macro investment rate was 8.78 percentage points higher on average when adjustment cost were considered than when adjustment cost were ignored.Therefore,the adjustment cost has a significant impact on the macro investment rate,that is,high marginal value of capital leads to high macro investment rate.Further analysis shows that China s welfare-maximizing macro investment rate is higher than the actual macro investment rate when adjustment cost are considered,indicating that China s macro investment rate is not too high.