城镇化进程中用水量增长的门槛效应与动态作用机制分析

城镇化是发展中国家21世纪的主要发展趋势,在很大程度上主导着人口、经济和产业结构等各方面的转变,成为拉动用水量增长的关键因素。城镇化进程中城镇居民收入、人口结构、人口密度和人力资本等因素的变化,使得城镇化并非表现为线性发展规律,最终导致用水量也存在相应的门槛效应并呈现阶段性增长特征。本文首先对我国各地区城镇化水平和用水量进行统计分析,从地区层面直观描述我国城镇化水平和用水量的变化特征,然后采用面板门槛模型研究城镇化、城镇居民人均收入、人力资本、城市人口密度和人口年龄结构对于用水量的门槛效应,搜寻在城镇化进程中各人口因素对用水量影响的门槛点并分析阶段性变化特征,最后结合PVAR模型研究城镇化进程中各人口因素对用水量的动态影响和作用机制。门槛回归结果发现:城镇化对用水量的影响具有明显的阶段性特征,分别以城镇化和人均收入为门槛变量,超越门槛点后城镇化对用水量的弹性系数分别呈现先升后降的倒"U"型和先降后升的正"U"型变化趋势;以人力资本为门槛变化量,城镇化对用水量的拉动作用则不断减弱。脉冲响应结果显示:城镇化对用水量具有长期且稳定的正向冲击,而居民收入和人口年龄结构对用水量的正向冲击则逐渐收敛于零,人口密度和人力资本对用水量均具有负向冲击,且人口密度的负效应不断增强,而人力资本的负效应不断减弱。方差分解的结果表明,目前我国用水量的增长受自身的影响较大,除年龄结构外,人口密度、居民收入、人力资本和城镇化也具有小规模的贡献程度。

Analysis on threshold effects and dynamic mechanism of water consumption growth in the process of urbanization

As a main trend of developing countries in the 21st century,urbanization dominated the transformation of population,economy and industrial structure,etc.,which became a key factor to drive water consumption growth.Due to the transformation of urban household income,population structure,population density and human capital,the influence of urbanization on water consumption shows staged features.In this paper,the urbanization level and water consumption in different regions of China are analyzed statistically,and the changes of urbanization level and water consumption are described from regional level.Then threshold model is applied to search the key turning points for water consumption and analyzed the relation between water consumption and urbanization.Then PVAR model is adopted to analyze the dynamic influence and mechanism of population on water consumption.Threshold results show:there are remarkable staged characteristics in the influence of urbanization upon water consumption.Taking urbanization and income as threshold variables respectively,the elasticity coefficients between urbanization and water consumption presents inverted "U-shaped" and "U-shaped" trend respectively.However taking human capital as threshold variable,the driving effect decreases with improvement of human capital.The results of the impulse response show:the impulse of urbanization on water consumption has long-term and stable positive effect,while the positive impulses of income and age structure converge to zero.Both of the impulses of population density and human capital are negative,however the effect of population density is increasing while the effect of human capital is decreasing.The result of variance decomposition shows that the growth of water consumption in China is influenced by itself.Besides age structure,population density,income,human capital and urbanization also have small contribution.