Towards sustainability: Evaluating energy efficiency with a super-efficiency SBM-DEA model across 168 economies

Enhancing energy efficiency (EE) is a crucial strategy for fostering sustainable development through the alignment of economic growth, energy conservation, emission mitigation, and social welfare improvement. It is widely recognized as the most accessible, secure, and cost-effective means of advancing sustainable development. However, many developing economies still exhibit remarkably low levels of EE, resulting in significant disparities compared to their developed counterparts. These disparities pose challenges to the realization of the United Nations' sustainable development goals (SDGs). In response to the limitations of extant EE definitions, our study proposes a redefined concept of EE within the sustainable development framework. Subsequently, we utilize the super-efficiency SBM-DEA model to assess the EE of 168 economies globally from 2000 to 2017, offering a detailed examination centered on spatiotemporal patterns and inequality. Key findings include: (1) Global EE initially displayed an upward trajectory, followed by a decline, with a persistent decrease post-2009; the impact of global financial crisis on EE varies across income groups of economies. (2) Spatially, EE exhibits a notable geographical clustering effect, with regions displaying distinct concentrations of high and low EE throughout the study period. (3) While global EE inequality has generally diminished, disparities within income groups have become the dominant source of EE inequality. Our research elucidates the intricate dynamics of global EE and underscores its integral role in the pursuit of sustainable development.