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

Table 4

The heterogeneity results.

Variables	Climatic zone			Economic development level
	Temperate monsoon	Temperate continental	Subtropical monsoon	High	Medium	Low
	(1)	(2)	(3)	(4)	(5)	(6)
		−4.7858	−0.3426	−1.6634	−0.3895
	(1.1101)	(3.7357)	(0.7564)	(1.0471)	(1.0467)	(1.1852)
Weather control variables	Yes	Yes	Yes	Yes	Yes	Yes
City control variables	Yes	Yes	Yes	Yes	Yes	Yes
City-fixed effects	Yes	Yes	Yes	Yes	Yes	Yes
Year-fixed effects	Yes	Yes	Yes	Yes	Yes	Yes
Observation	616	97	881	546	531	531
R ^2	0.5067	0.7692	0.5912	0.4995	0.4772	0.5064
Variables		Geographical location
		East		Central	West
		(7)		(8)	(9)
		0.4515			−1.5485
		(0.8425)		(1.1188)	(1.2900)
Weather control variables		Yes		Yes	Yes
City control variables		Yes		Yes	Yes
City-fixed effects		Yes		Yes	Yes
Year-fixed effects		Yes		Yes	Yes
Observation		728		531	349
R ^2		0.4717		0.5348	0.6906

Note: (1) Robust t-values are stated in parentheses below coefficients and clustered by city level. (2) The symbols , , and represent a significance level of 10%, 5%, and 1%, respectively.(3) Sample cities (1)–(3) are divided into temperate monsoon climate, temperate continental climate, and subtropical monsoon climate, respectively, according to climate zone characteristics. Sample cities (4)–(6) are categorized into high-, medium-, and low-level economic development, respectively, according to the level of per capita GDP, and sample cities (7)–(9) are divided into eastern, central, and western cities, respectively, according to their geographical locations.