The Missing Variable in Europe's Research Paradox: Evidence from Portugal

Abstract: Rodríguez-Navarro (2026) argues that Europe's limited production of scientific breakthroughs stems primarily from research inefficiency, measured by the conversion of highly cited papers (top 10%) into exceptionally cited papers (top 1%). This comment examines that proposition using Portugal as a boundary case. Applying the same indicators, estimator and CWTS Leiden Ranking data to the country's six largest universities (2020–2025 editions), we find no evidence of an efficiency deficit. Nevertheless, the expected output of breakthrough papers remains extremely small because the underlying stock of highly cited publications is itself limited. Portugal therefore distinguishes two mechanisms that may underlie Europe's breakthrough deficit: research efficiency and scientific scale. While large research systems may be constrained primarily by inefficient conversion of highly cited research into exceptional discoveries, smaller systems can achieve benchmark efficiency yet remain limited by insufficient critical mass. These findings indicate that improving research efficiency alone cannot substantially increase breakthrough production once benchmark performance has been attained. For smaller European research systems, expanding the volume of internationally competitive research may be as important as further gains in efficiency, suggesting that European science policy should address scientific scale alongside research efficiency.