基于PSM-DID分析创建国家卫生城市对我国231个地级市环境水平的影响

PSM-DID-based analysis of the impact of creating national hygienic cities on the environmental levels of 231 prefecture-level cities in China

目的分析创建国家卫生城市(简称“创卫”)对我国地级市环境水平的影响。方法本研究纳入我国2007-2019年期间的104个卫生城市,通过将倾向性得分匹配(propensity score matching,PSM)与双重差分法(difference-in-difference,DID)相结合的方法,选择127个城市作为对照组,分析“创卫”活动对我国地级市环境水平的影响。反映环境水平的指标包括生活垃圾无害化处理率、污水处理厂处理率、废水排放量、烟粉尘排放量和绿化覆盖率,调整经济发展水平、人口密度、技术创新程度、工业化程度、年均温度、年均相对湿度、年均日照时间、年均风速和年均气压,通过假设政策分别提前3、4和5年和随机化处理组和对照组,进行安慰剂检验。结果创建卫生城市使垃圾处理率、污水处理率、市辖区绿化覆盖率分别显著提高11.8%(P=0.038)、8.1%(P=0.035)和16.5%(P=0.016),废水排放显著下降9.5%(P=0.049)。结论“创卫”之后,地级市的垃圾处理率、污水处理率和市辖区绿化覆盖率水平显著提高。

Objective To analyze the impact of creating national hygienic cities on the environmental levels of prefecture-level cities in China.Methods This study included 104 hygienic cities in China during the period of 2007-2019,and selected 127 cities as the control group by combining propensity score matching(PSM)and difference-in-difference(DID)to analyze the impact of creating hygienic activities on the environmental level of prefecture-level cities in China.The following environmental indicators were analyzed:the rate of harmless treatment of domestic waste,the rate of wastewater treatment in sewage treatment plants,the amount of wastewater discharges,the amount of smoke and dust emissions,and the rate of green coverage.The following factors were adjusted:the level of economic development,population density,the level of technological innovation,the degree of industrialization,average annual temperature,average annual relative humidity,average annual sunshine duration,average annual wind speed,and average annual air pressure.Placebo tests were conducted by assuming policies 3,4,and 5 years in advance and randomizing the treatment and control groups.Results Creating hygienic cities resulted in significant increases in the waste treatment rate(11.8%,P=0.038),wastewater treatment rate(8.1%,P=0.035),and municipal green coverage rate(16.5%,P=0.016),as well as decreases in wastewater discharges(9.5%,P=0.049).Conclusion Creating national hygienic cities significantly increases the waste treatment rate,wastewater treatment rate,and municipal green coverage rate of China’s prefecture-level cities.