雾霾治理中的“政治性蓝天”——来自中国地方“两会”的证据

目的/意义合理的环境政策工具是保障可持续发展的重要依据。设计/方法运用双重差分法（DID）和基于倾向得分匹配后的双重差分法（PSM-DID），分析了2016年杭州召开“G20峰会”前实行的命令控制型环境政策对空气质量的影响。结论/发现（1）长期政策有效改善了空气质量，其效果明显好于短期政策，保障了“G20峰会”前后杭州市空气的优良品质；（2）长期政策创造的蓝天是稳定持续的，“G20峰会”前后空气质量未出现大的波动或反弹现象；（3）“G20峰会”长期政策具有长期效应，长期内空气质量保持良好水平，未出现恶化趋势。在考虑了共同趋势、不同污染物形式、更换不同样本以及选择不同模型后仍然稳健。

The promise of Beijing: evaluating the impact of the 2008 Olympic Games on air quality

[Purpose/Significance] Reasonable environmental policy tools are the important basis for sustainable development. [Design/Methodology] In this paper, the Differences-in-Differences (DID) and the Propensity Score Matching-Differences-in-Differences (PSM-DID) based on the propensity score matching are used to analyze the impact of the command-controlled environmental policy on the air quality before the “G20 Summit” held in Hangzhou in 2016. [Conclusions/Findings] (1) The long-term policy has effectively improved air quality, and its effect is obviously better than the short-term policy, which guarantees the excellent quality of the air in Hangzhou before and after the “G20 Summit”. (2) The blue sky created by long-term policy is stable and continuous. There is no big fluctuation or rebound in air quality before and after the “G20 Summit”. (3) The long-term policy of the “G20 Summit” has a long-term effect. The air quality has been maintained at a good level for a long time, and there is no deterioration. The results of this paper are still robust after considering common trends, different forms of pollutants, changing different samples, and selecting different models.