Beyond Single-Dimension Metrics: Environmental Policy Performance Index and Its Implication for Environmental Governance in Europe

This paper presents the Environmental Policy Performance Index (EPPI), a two-dimensional composite index designed to evaluate the effectiveness of environmental policy in a comprehensive and balanced way. The EPPI integrates both policy inputs – such as government expenditures on environmental protection and pollution-related taxes – and policy outputs, measured through indicators of environmental quality. By combining these dimensions, the index enables a more nuanced understanding of how well public policy efforts are translated into tangible environmental outputs. Applied to 23 European countries over a multi-year period, the EPPI addresses key limitations of existing one-dimensional indices, which often assess either policy efforts or results in isolation. Our findings reveal that while some countries demonstrate strong alignment between policy intensity and environmental performance, others invest substantial resources without achieving commensurate improvements – suggesting the presence of inefficiencies, behavioural inertia, or structural constraints. To ensure comparability, both EPPI subindices are constructed using consistent data sources and timeframes. Importantly, we do not claim a causal relationship between inputs and outputs; rather, the EPPI is intended to support descriptive and comparative assessment. Countries are grouped into four performance profiles based on their input-output balance, providing actionable insights for policymakers. By offering a replicable and transparent methodology, the EPPI represents a methodological advancement with broader applicability beyond Europe. It contributes to the growing need for reliable and multidimensional tools that can inform environmental governance, track progress toward sustainability goals, and enhance international policy learning.