Table 5 The robustness test of the cross terms of industrial characteristic variable and trade cost density (general)

c _i  × T _t

−3.305***

−3.777***

(−8.20)

(−7.06)

c _i  × Labor productivity index _it

−0.001 ***

(−2.18)

c _i  × R & D intensity _it

2.678***

(2.25)

Industrial fixed effect

Yes

Yes

Time-fixed effect

Yes

Yes

R ²

0.7007

0.7014

Observation

153

153