“2+26”城市雾霾治理政策效果评估

Quantitative assessment of the effects of the air pollution control policy in the ‘2+26’ cities

文章将《京津冀及周边地区2017年大气污染防治工作方案》和其后续“攻坚行动方案”的发布作为准自然实验,使用双重差分模型(DID)评估大气污染治理的政策效果。回归结果发现:(1)“方案”的发布对于“2+26”城市的空气具有显著的改善作用,并通过了稳健性检验,构成雾霾的主要污染物PM_(2.5)、PM_(10)和AQI的改善程度最明显,SO_(2)、CO和NO_(2)的改善幅度次之,但O_(3)浓度在政策处理期内不降反升,说明近年来O_(3)污染程度加剧,亟须引起关注。(2)长期视角下SO_(2)和NO_(2)的治理效果较短期情况下相比有所提升,说明有些大气污染物仍然具有进一步改善的潜力,印证了大气污染治理是一项长久的“攻坚战”。(3)引入空间DID分析,通过空间杜宾和双重差分的嵌套模型,放松个体相互独立的假设,从空间维度探讨“方案”的政策效果,对比空间视角下的直接效应与间接效应得出,区域联防联控大气治理手段相比单一地区空气质量改善政策而言能够使得治理效果事半功倍。(4)使用中介效应模型,探讨了“方案”通过减少工业产值占GDP的比重和减少能源消费总量达到空气质量改善的两种作用机制。最后,文章为接下来进一步有效治理大气污染提出了相关的政策建议。

Taking the release of the ‘2017 Work Plan for Prevention and Control of Atmospheric Pollution in Beijing-Tianjin-Hebei and Surrounding Areas’and its follow-up‘Action Plan for Comprehensive Management of Air Pollution’as a quasi-natural experiment,this article employed a difference-in-differences (DID) model to evaluate the effects of the air pollution control policy.Our regression results showed that:(1) The release of the plans could significantly improve the air quality of the ‘2+26’ cities.The improvement of PM_(2.5),PM_(10)and AQI,the main pollutants constituting haze,was the most obvious,followed by SO_(2),CO and NO_(2).However,O_(3) concentration did not decrease but increased during the policy period,indicating the intensification of the degree of O_(3) pollution in recent years,which needs to be paid attention to.The robustness test showed that the findings remained valid.(2) From the long-term perspective,the treatment effects of SO_(2) and NO_(2) improved compared with those in the short-term,indicating that some air pollutants still have the potential for further improvement in the long-term,confirming that air pollution control is a long-term tough battle.(3) Based on the spatial DID analysis and the relaxed assumption of individual independence through the nested spatial Durbin model and DID model,this article discussed the policy effects of the aforementioned plans from the spatial dimension,compared the direct and indirect effects,and drew the conclusion that regional joint prevention and atmospheric control action can achieve twice the result with half the effort compared with individual implementation of air quality improvement policy in separate cities.(4) Using the intermediary effect model,this article further explored the two mechanisms of air quality improvement by reducing the proportion of industrial output value in GDP and reducing total energy consumption.Finally,this article puts forward relevant policy recommendations for further effective control of air pollution.