The decoupling frontier: efficiency, inequality, and biocapacity in the global search for absolute sustainability

Introduction Conventional approaches for decoupling economic growth from resources often emphasize regression-based evaluations while omitting structural heterogeneity and biophysical limits. The present study aimed to examine country-specific pathways for absolute decoupling of fossil material use within the planetary boundaries. Methods Using a panel dataset encompassing information from 85 countries over the period of 2002 to 2023, we approximated the material efficiency scores via stochastic frontier analysis (SFA) by assuming half-normal and exponential distributions. Results The results show that the biocapacity overshoot varies irregularly and ranges between 9.5% and 19% of the national averages; this trend indicates the cyclic fragility of decoupling. Furthermore, the results indicate high material inequality (Gini = 0.55), including the fact that nearly two-thirds of the fossil-based material resources were consumed by approximately 20% of the global population. Rwanda, Myanmar, and Oman were found to be the most efficient countries, whereas high-income economies were faced with diminishing returns. Additionally, we proposed an efficiency-adjusted index above USD 650,000 per ton based on global climate investment at the forefront. We found that the richest or the most polluting countries did not provide the greatest marginal benefits; instead, countries with structurally inefficient economies could provide massive economic and ecological benefits through specific policy interventions. Discussion The present work expands on this frontier of knowledge by shifting the decoupling paradigm to ecological feasibility, which indicates that the highest marginal gains are available in structurally inefficient economies rather than polluting nations. By integrating SFA in this work, we identified the absolute minimum achievable fossil footprints by prioritizing equity sensitive climate finance.