Building Better Cities: Evaluating the Effect of Circular Economy City Construction on Air Quality via a Quasi-Natural Experiment

Table 2

Baseline regression results for the impact of circular economy pilot cities on air quality (PM_2.5 in ).

Variables	Air quality
	(1)	(2)	(3)	(4)	(5)	(6)
(0.5665)	(0.5990)	(0.5811)	(0.6167)	(0.6391)	(0.6683)
Weather control variables	No	Yes	No	Yes	No	Yes
City control variables	No	Yes	No	Yes	No	Yes
City-fixed effects	Yes	Yes	Yes	Yes	Yes	Yes
Year-fixed effects	Yes	Yes	Yes	Yes	Yes	Yes
Observations	1610	1608	1554	1552	1274	1272
	0.4397	0.4574	0.4371	0.4572	0.4366	0.4595

Note: (1) The weather control variables include the average wind speed, the sunshine hour, and the average air pressure index. (2) The city control variables include the industrial sulfur dioxide emissions, the emissions of the industrial smoke and dust, the treatment rate of the domestic sewage, the rate of the comprehensive utilization of the industrial solid waste, the rate of the harmless treatment of the domestic garbage, the rate of the innocuous treatment of the domestic garbage, the industrial wastewater discharge, the green coverage in the built-up areas, the actual foreign investment, the total industrial output value of the enterprises above the designated size, the number of the registered unemployed in the urban areas at the end of the year, the population density, the number of the public automobiles and electric vehicles per 10,000 people, and the proportion of the secondary industry in GDP. (3) Robust t-values are stated in parentheses below coefficients and clustered by city level. (4) The symbols , , and represent a significance level of 10%, 5%, and 1%, respectively.