[Retracted] Environmental Efficiency of Node Cities in Chinese Section of Silk Road Economic Zone and Its Influencing Factors

Table 4

Details about independent variables.

Name	Symbol	Meaning and unit	Predicted sign
Economic scale	Ln (GP)	Per-capita GDP (yuan/person)	Positive
	GR	Regional GDP as a proportion of national GDP (%)	Positive
Industrial structure	PI	Secondary industry output as a proportion of regional GDP (%)	Unknown
Government regulation	FI	Regional industrial pollution management investment as a proportion of regional GDP (%)	Unknown
Opening-up	DT	Trade dependence: total value of import and export as a proportion of GDP (%)	Positive
	DC	Foreign fund dependence: actually utilized foreign direct investment as a proportion of GDP (%)	Unknown
Technological progress	Ln (TI)	Number of authorized patents	Positive
Regional feature	Ln (PD)	Population density: ratio of the year-end total population to the regional area (persons/km^2)	Unknown