Assessing China's regional efficiency of energy-saving and emission reduction using the target orientation approach of extended DDF model

Based on the target of energy-saving and emission reduction (ESER) in the national five-year plan in China,an extended directional distance function model (E-DDF) including undesirable input and undesirable output is proposed,and energy-saving efficiency,emission reduction efficiency,ESER efficiency are defined.Then the weighted directional distance function model is constructed for the total factors efficiency index model of ESER to reflect its dynamic change.The results show that the ESER efficiency continues to rise during the three five-year plan periods (2006-2017),and the efficiency score of the east area are higher than those of central and west area.The disparity and change of energy-saving efficiency among difference regions are not obvious,but the disparity and change of emission reduction efficiency are the main reasons for the improvement and change of ESER efficiency index.In the long run,the ESER efficiency is in a dynamic upward trend,and the effect of technological progress is more obvious compared with technical efficient index.