Table 7.

Sensitive analysis test by panel quantile regression.

Variables	Coefficient	Standard Error	t-statistics	Probability value
Constant	23.419	1.533	15.078	0.000
COM_DIS	0.115	0.045	2.517	0.012
CHEM	0.281	0.176	1.591	0.111
CHEM × CO2	0.046	0.007	6.449	0.000
CHEM × FFUEL	−0.008	0.002	−3.768	0.000
GDPpc	−0.0007	6.87E-05	−10.387	0.000
SQGDPpc	5.00E-09	4.54E-10	11.016	0.000
HLT_EXP	0.00074a	0.0003	2.165	0.030
LB_HWF	0.054	0.033	0.814	0.100
POP_DEN	−0.002b	0.0017	−0.1.260	0.207

Note:

^aand.

^bshows the quantile regression estimates at 10th quantiles and 30th quantiles respectively.