环保投资占比最优化:基于生态效率的考量

将生态效率作为综合衡量环保投资效益的指标，利用中国2003~2015年30个省（区、市）的数据，研究生态效率与环保投资的双向影响关系，并估算环保投资占比的最优区间.结果表明：（1）2003~2015年，全国平均生态效率整体呈略微下降趋势，由0.79下降至0.69.（2）环保投资占比对生态效率构成倒"N"型影响，经历"降低-提升-抑制"3个阶段.根据所获数据进行计算和推测，当环保投资占比处于0~1.50%时，环保投资不能有效防止生态效率下降；占比处于1.50%~3.30%时，环保投资能显著提升生态效率，至3.30%时达到最大值；占比大于3.30%时，过多的环保投资投入反而使生态效率下降.（3）省际生态效率具有空间溢出效应，省级政府环保投资策略具有协同性.

Optimizing the ratio of environmental protection investment: based on the eco-efficiency

The eco-efficiency was used as an indicator to comprehensively measure the benefits of environmental protection investment in this study. The data of 30 Chinese provinces (autonomous regions and municipalities) was from 2003 to 2015. The bidirectional impact relationship between eco-efficiency and environmental protection investment was investigated in this study. The optimal ratio of environmental protection investment was evaluated in the present study. Results indicated, (1) the national average eco-efficiency showed a slightly downward trend from 2003 to 2015, which was down from 0.79 to 0.69. (2) The ratio of environmental protection investment had inverted N-shaped impact on eco-efficiency and experienced three stages of declining, rising and restraining. Similarly, the calculation and speculation of data indicated that the environmental protection investment could not prevent eco-efficiency to decline with 0 to 1.50% ratio of investment. The environmental protection investment could significantly improve eco-efficiency when the ratio varied from 1.50% to 3.30%. It reached the maximum level with the 3.30% of investment ratio. On the other hand, when the ratio exceeded the limit, eco-efficiency declined instead. (3)The eco-efficiency of provincial regions had characteristic of spatial spillover and the environmental protection investment strategy of provincial government promoted cooperation among provinces.