The Impacts of Freight Trade on Carbon Emission Efficiency: Evidence from the Countries along the “Belt and Road”

Table 4

Panel unit root tests.

Variable	LLC test	Breitung test	IPS test	Fisher test
LCTCEI	−8.8635	−1.6509	−9.4577	−12.0121
LITCEI	−7.3542	−2.0389	−6.8583	−10.3107
LGTCEI	−10.2806	−3.2652	−6.4187	−8.8358
LBPR	−8.1387	−3.6343	−8.5008	−13.0389
LTGR	−11.2486	−7.1752	−10.0967	−11.6917
LIFT	−5.6338	−5.1729	−2.9788	−7.8499
LFDI	−2.5586	−4.6094	−3.3514	−8.2880
LRED	−7.5905	−3.3552	−5.9387	−12.0561
LRFE	−6.4840	−1.4404	−4.2362	−7.1025
LPatent	−4.5581	−2.7424	−3.6996	−10.3693
LRID	−4.1813	−1.4641	−3.0617	−10.9062

, , and .