The diversity of institutional rules as engine of change

International audienceThe target paper by Elinor Ostrom in this Special Issue carries a clear message about her research agenda: be attentive to institutional diversity, be aware of the danger of 'monoculture' and 'monocropping' of rules. Although Ostrom was fully aware of the necessity to focus on relevant and simplified variables in order to build general explanations, she deliberately adopted a bottom-up research strategy that opposes the top-down approach dominating social sciences. Her framework, developed through extensive field studies, shows the central role of "clusters" of rules in defining institutions and understanding how they change. My discussion is organized around this privilege conferred to rules. Section 2 posits her contribution, particularly her IAD model, in relation to New Institutional Economics. Section 3 focuses on what I consider her main contribution: her analysis of rules as the strategic point through which changes happen. Section 4 discusses some methodological issues, and Sect. 5 concludes