Table 6.

The results of the mechanism analysis.

Variables	Structure effect
	Air quality	Advancement of the industrial structure	Air quality	Industrial structure rationalization	Air quality
	(1)	(2)	(3)	(4)	(5)
treatit	−1.682∗∗∗	0.496	−1.615∗	−0.653	−1.833
	(0.599)	(0.405)	(0.863)	(0.996)	(0.234)
Advancement of the industrial structure			−0.026
			(0.108)
Industrial structure rationalization					−5.652
					(3.118)
_cons	−79.011∗	110.861∗∗∗	−76.105	−65.345	−49.545
	(81.352)	(36.390)	(86.305)	(41.236)	(56.921)
Weather control variables	Yes	Yes	Yes	Yes	Yes
City control variables	Yes	Yes	Yes	Yes	Yes
City-fixed effects	Yes	Yes	Yes	Yes	Yes
Year-fixed effects	Yes	Yes	Yes	Yes	Yes
Observation	1608	1608	1608	1608	1608
R 2	0.457	0.849	0.457	0.029	0.011
Variables	Scale effect		Technology effect
	Energy consumption per unit of GDP	Air quality	Technological progress		Air quality
	(6)	(7)	(8)		(9)
treatit	−0.044∗∗∗	−1.819∗∗	0.001		0.988
	(0.017)	(0.843)	(0.009)		(0.760)
Energy consumption per unit of GDP		−4.310∗
		(2.394)
Technological progress					3.622
					(1.543)
_cons	4.047∗∗∗	−61.572∗	56.345		39.298
	(1.692)	(85.531)	(35.451)		(51.332)
Weather control variables	Yes	Yes	Yes		Yes
City control variables	Yes	Yes	Yes		Yes
City-fixed effects	Yes	Yes	Yes		Yes
Year-fixed effects	Yes	Yes	Yes		Yes
Observation	1608	1608	1608		1608
R 2	0.756	0.459	0.122		0.168

Note: (1) The control variables are the same as the benchmark regression equation. (2) The symbols ^∗, ^∗∗, and ^∗∗∗ represent a significance level of 10%, 5%, and 1%, respectively.