control group before western development

experimental group before western development

difference between control group and experimental group before western development

control group after western development

experimental group after western development

difference between control group and experimental group after western development

test result of difference-in- difference

lngdp

13.652

13.471

−0.181

14.723

14.232

−0.491

−0.310

sem

0.110

0.045

0.118

value of t

−1.660

−11.000

−2.620

P > |t|

0.098*

0.000***

0.009***