Does China's carbon emission trading policy improve regional energy efficiency?-an analysis based on quasi-experimental and policy spillover effects

Carbon emission trading policy is of great importance for addressing climate change and reducing carbon emissions. Reducing carbon emissions could further affect energy efficiency (EE). Based on the data from 30 provinces in China from 2006 to 2017, this paper first calculated EE by using the super slack-based model (Super-SBM) and then analysed the theoretical mechanism of the impact of carbon emission trading policy on EE. We also used a difference-in-difference (DID) model and mediation effect model for empirical analysis. Finally, we established the spatial difference-in-difference (SDID) model to test the policy spillover effects of carbon emission trading policy. The results showed that the high EE areas have gradually shifted to the central and eastern regions during 2006-2017 in China. The EE value in the pilot area of the carbon emission trading policy was obviously higher than that in the non-pilot area. Carbon emission trading policy had a significant positive effect on improving EE overall. In particular, green technology innovation and energy structure both had positive mediation effects on carbon emission trading policy affecting EE. However, the industrial structuring adjustment had no significant mediation effect in its influencing mechanism. Additionally, the spatial spillover effects test showed that the carbon emission trading policy had a positive effect on the EE of the pilot areas but a negative effect on that of the non-pilot areas.