How does high-speed railway affect green innovation efficiency? A perspective of innovation factor mobility

Growth effects of high-speed railway (HSR) have received increasing attention from scholars. However, little attention has been paid to HSR's effect on green innovation. To bridge this gap, using the difference in differences method, this paper aims to provide insights on how HSR affects green innovation from the perspective of innovation factor mobility, by employing the 108 cities in the Yangtze River Economic Belt of China in 2005-2016. The main findings are as follows: (1) Although the effects derived from HSR are heterogeneous, HSR significantly drives green innovation efficiency by 11.3%, which reveals that HSR is a critical variable for understanding the growth of green innovation. (2) This paper presents evidence that HSR promotes the mobility of innovative factors and then contributes to green innovation efficiency, based on which heterogeneity is explored. (3) HSR's effect on green innovation efficiency has a dynamic experience over time and shows an inverted U-shaped curve characterized by increased first and then decreased, which peaks in the 5th or 6th year. (4) Green innovation growth effects of HSR have spatial proximity: for every 1% increase in distance, the green innovation effect decreases by 0.0061%-0.0124%. A farther distance to an HSR station induces a lower growth effect. (5) This paper concludes with recommendations to improve green innovation through HSR construct and innovative factor mobility.