Is the Porter Hypothesis more relevant today than 30 years ago? Bibliometric and content analysis

More than three decades after its introduction, the Porter Hypothesis (PH), which argues that well-designed environmental regulation can stimulate innovation and even enhance productivity, remains highly relevant. This study presents the first comprehensive review integrating bibliometric and qualitative content analysis, offering a systematic and current overview of the field and identifying how research themes, methods, and empirical focus have evolved over time. First, bibliometric analysis examines 800 PH-related articles (1991-2024), comparing developments across an early (1991-2013) and a later (2014-2024) period. The analysis reveals a marked increase in publication activity, methodological advancement, and policy relevance in the past decade, especially in China. Second, the qualitative content analysis of the 15 most influential studies confirms strong support for the weak version of the PH and conditional support for the strong version, particularly under flexible, market-based regimes. The findings also show a shift from theory-driven toward empirically grounded research, employing advanced econometric techniques and broader indicators that increasingly integrate green dimensions (e.g., green innovation, green total factor productivity, sustainable development). Third, based on the identified research trends and knowledge gaps, the study highlights that smart and context sensitive regulatory frameworks, integrating market-based instruments, innovation incentives and regional differentiation, can effectively align environmental protection with sustainable economic performance. Overall, the study maps the evolution of PH research, outlines directions for future inquiry and environmental policy, and aims to serve as a reference point for scholars seeking to further advance the theoretical and empirical development of the PH.