	(1)	(2)	(3)	(4)
VARIABLES	AOI	AOO	AOI	AOO
				
DID	-0.1876325**	-0.1122230*	0.0707856*	0.0987758**
	(-2.506)	(-1.747)	(1.663)	(1.997)
Size	0.4614603***	0.4836395***	0.3520942***	0.4683797***
	(8.779)	(8.844)	(8.841)	(7.996)
Lev	0.0384954	0.0496956	0.0468563	0.1183369
	(0.391)	(0.566)	(0.574)	(1.158)
FirmAge	0.4786648	0.5367210*	0.2661643	0.4503051**
	(1.332)	(1.784)	(1.432)	(2.085)
PR	0.1252985***	0.2850515***	0.0907965***	0.3470633***
	(5.379)	(9.856)	(5.019)	(10.490)
Employee	0.4601595***	0.4318947***	0.2402377***	0.4136414***
	(9.134)	(9.871)	(9.157)	(9.361)
FIXED	-0.1851283	-0.1287206	0.1081073	-0.1116617
	(-0.562)	(-0.397)	(0.604)	(-0.537)
Constant	3.2906088***	3.2709479***	6.0073848***	3.1471142***
	(2.998)	(3.138)	(8.724)	(3.152)
				
Observations	4,571	4,571	5,160	5,160
R-squared	0.263	0.445	0.284	0.486
Number of firm_id	1,035	1,035	1,153	1,153
年份固定效应	YES	YES	YES	YES
个体固定效应	YES	YES	YES	YES
Robust t-statistics in parentheses				
*** p<0.01, ** p<0.05, * p<0.1				
