On the output side, they used the Human Development Index to capture socioeconomic progress as a desirable outcome, while carbon dioxide, methane, and nitrous oxide emissions entered the analysis as undesirable externalities that sustainable productivity growth should push downward. The results show that roughly 53 percent of the countries in the sample recorded positive growth in sustainable total factor productivity during the study period. Technological innovation, rather than improvements in technical efficiency, emerged as the primary driver of that growth.

In other words, countries advanced mainly by adopting and developing new sustainable technologies, not by simply closing the gap between their current practices and the existing best-practice frontier. Countries that strategically invested in sustainable technologies stood out as top performers, registering significant gains in sustainable productivity relative to their peers. This pattern identifies deliberate technology investment as a distinguishing feature of the leaders in this sustainability metric.

Perhaps the most striking finding concerns convergence. The study found no evidence of overall global convergence in sustainable total factor productivity, meaning the gap between the highest and lowest performing countries has not been narrowing uniformly. Instead, the club convergence test revealed the formation of three distinct convergent clubs, groups of countries whose productivity trajectories are merging with one another while remaining separate from other groups.

These clubs reflect heterogeneous paths in sustainable productivity growth. Rather than all countries drifting toward a common productivity level, nations appear to be sorting into clusters with similar growth dynamics. The authors interpret this as evidence that countries are merging into groups with comparable productivity performance rather than converging uniformly across the global economy.

The analysis, published as open access research, offers a framework that integrates ecological regeneration and human development into productivity measurement.

Subject of Research: Club convergence in sustainable total factor productivity measured with a slacks-based global Malmquist–Luenberger index including undesirable outputs

Article Title: Analysing club convergence in sustainable total factor productivity using SBM based global Malmquist–Luenberger Productivity Index with undesirable outputs

Article References: Zaman, A. U., & Zaman, M. S. (2026). Analysing club convergence in sustainable total factor productivity using SBM based global Malmquist–Luenberger Productivity Index with undesirable outputs. Discover Sustainability. https://doi.org/10.1007/s43621-026-05083-8

Image Credits: AI Generated

DOI: 10.1007/s43621-026-05083-8

Keywords: sustainable total factor productivity, club convergence, Malmquist-Luenberger index, slacks-based measure, data envelopment analysis, biocapacity, Human Development Index, undesirable outputs, greenhouse gas emissions, technological innovation, Analysing, club