<p>The nexus between economic growth and sustainable development constitutes a central theme in current debates on sustainability and policy formulation. Measuring this relationship, as well as identifying evolutionary patterns toward sustainability, continues to pose a challenge for both national and international institutions. To address this gap, this paper pursues a dual purpose. First, it proposes a new indicator— Sustainable Strategic Orientation—which captures the strategic effort made by each country toward achieving sustainable development. Second, the empirical validation of this indicator is conducted by applying a quadratic model based on the Environmental Kuznets Curve framework to data from 46 high- and middle-income countries between 2010 and 2017. The results show that economic growth and sustainable development are coupled up to a certain threshold and that sustainable efforts act as a moderator of this threshold level, pushing it in opposite directions depending on a nation’s level of wealth. These findings extend the existing literature and offer valuable insights for policymakers in designing sustainable public policies for high- and middle-income countries.</p>