Towards the road of eco-efficiency improvement: evidence from China's economic and technological development zone

The economic and technological development zone (ETDZ) serves an essential role in driving green development and ecological civilization. Therefore, it is crucial to investigate the impact of ETDZs on eco-efficiency for sustainable development. This paper investigates the impact of the establishment of ETDZs on eco-efficiency by constructing a differences-in-differences (DID) model on the basis of 253 cities in China from 2004 to 2017 as the dataset. This paper also explores the possible intrinsic impact mechanisms through the channels of industrial structure and technological innovation by constructing a mediating effect model, and the heterogeneous effects of ETDZs on eco-efficiency from the perspectives of regional imbalance and city class heterogeneity. Statistical results report that ETDZs significantly positively affect eco-efficiency and such effects are most significant in the first year after the establishment of ETDZs. Industrial structure upgrading and technological innovation are essential role mechanisms for ETDZs to enhance eco-efficiency. Besides, the enhancement effect of ETDZs on eco-efficiency is only observed in the eastern part of the city, with an insignificant inhibitory effect in central and western parts of the cities. However, the establishment of ETDZs in cities with higher city classes is more beneficial to improve eco-efficiency.