The article presents a new way to measure how well countries are developing sustainably. The researchers created a special index that looks at economic, social, and environmental factors. They used data from 140 countries over 25 years to compare their development. High-income countries are doing well economically but harming the environment more. Low-income countries struggle economically but have less environmental damage. Social sustainability results vary. The study suggests that countries should focus on improving their economic and social aspects while also protecting the environment.