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 10

Mediation robustness test results by using the Bootstrap method.

	Estimated value	Standard error	Z-statistic	value	95% confidence interval
					Lower limit	Upper limit
Mediation effect of the supererogation level	0.0059	0.0044	1.35	0.176	−0.0026	0.0144
Mediation effect of the rationalization level	0.0079	0.0036	2.21	0.027	0.0008	0.0150
Overall mediation effect	0.0138	0.0050	2.77	0.006	0.0040	0.0236