Evaluation of the Effects of the Belt and Road Initiative on the Unified Economic and Environmental Efficiency of Transportation Infrastructure in China Based on Range-Adjusted Measure Model and Difference in Difference Model

Table 8

Mediation effect results obtained by the Bootstrap method.

	Estimated value	Standard error	Z-statistic	value	95% confidence interval
					Lower limit	Upper limit
Mediation effect of the supererogation level	0.0011	0.0032	0.33	0.738	−0.0052	0.0074
Mediation effect of the rationalization level	0.0088	0.0040	2.21	0.027	0.0010	0.0166
Overall mediation effect	0.0098	0.0042	2.32	0.020	0.0015	0.0182