Regional difference in global unified efficiency of China-Evidence from city-level data.

As the world's most energy-consuming and carbon-emitting country, China faces enormous pressures on energy conservation and emission reduction, and improving energy efficiency is one of the most important ways to save energy and reduce emissions. Using the city-level panel data in China during 2013-2017, we apply the global non-radial directional distance function (NDDF) to estimate the global unified efficiency (GUE) of each city as well as their driving forces, and identify the change of efficiency performance. The results indicate that the average GUE changed -1.0%, 1.2%, 6.0% and 7.0% during 2013-2014, 2014-2015, 2015-2016 and 2016-2017, respectively. The more developed Central China and the relatively underdeveloped Northwest China have high GUE, while the lower GUE exists in the Northeast and North China regions with greater industrial transformation and upgrading pressures. In general, the global unified efficiency of each region increases over time.