Measuring Change: The Art and Science of Impact Assessment serves as a comprehensive resource for policymakers, researchers, and practitioners seeking to understand how policies and projects influence societies and economies. It presents a balanced approach, integrating quantitative rigor with qualitative insights to examine key methodologies, including baseline studies, modeling, counterfactual analysis, and participatory assessment. The book emphasizes stakeholder engagement, ethical considerations, and technological advancements such as GIS, machine learning, and big data. Through case studies, practical frameworks, and emerging trends, it provides a structured approach to designing and evaluating interventions, promoting informed and sustainable decision-making.