Since the 1990s, poverty and the ways to reducing it have become a central paradigm in development economics, not only in academia but among the international financial institutions (the World Bank and the International Monetary Fund). Indeed, after WWII, thinking on development was focused on growth. A major shift occurred in the late 1990s, which has consisted in the replacement of 'growth' or 'development' as a goal of policymakers and international institutions and a central theme of research in development economics, by poverty and its reduction, together with an expansion of the meanings of the concept of poverty. The key points of the paper are that this shift represents a crucial turning point in the conceptual framework of economic thought regarding developing countries. It represents a narrowing of the agenda of governments vis-à-vis the previous one of growth and development, and the acceptance that development is no longer the priority goal of public policies, of governments and their citizens, and that the previous actions, policies and research elaborated over decades since the beginnings of development economics were in fine a failure. This shift is also an implicit substitution of difficult objectives with highly complex causal processes for concepts that can be measured and easier short-terms goals, such as lifting up specific groups of a population above a poverty line. These new objectives are also more consensual and attractive. The paper firstly presents key steps of the evolution of the thinking in development economics since WWII, then critically assesses the conceptual framework that has emerged at the end of the 20th century regarding poverty in developing countries, in particular its multidimensionality and the pre-eminence of measurement issues and quantification. It finally analyses the associated shift in policy-making as a result of reciprocal exchanges between academic research and policymakers and donors, which have helped to consolidate the new paradigm.< Réduire