To reach the UN’s Sustainable Development Goals, humanity should improve its capacity to achieve well-being and development while reducing its environmental impact. This calls for increased efficiency in the process of transforming natural resources into well-being. We present here a novel indicator called Ecological Efficiency and developed to capture this important aspect of the human-environment relation. We found large differences in efficiency among world countries. We then analyzed the relation between our indicator and several country-level variables encompassing different human dimensions, such as economic, political, and demographic. Results highlighted that demography affects Ecological Efficiency more than other factors.