Résumé : Based on the premise ‘what we measure affects what we do’, this work seeks to address the following key question: What are the characteristics of the knowledge produced by the Rule of Law Index, WGI Rule of Law Indicator, Doing Business Indicators and the Global Competitiveness Index about the rule of law and business regulation respectively, and to what extent can this knowledge be used to assess and compare legal systems? My objective is to address the gap between, on the one hand, policy and scientific approaches to indicators and, on the other hand, legal scholarly approaches. The former tend to be specialized, mathematical and outcome-oriented, focusing on how to produce appropriate measures of social –and legal- phenomena. The latter assume an external point of view and are often verbal and critical. They focus generally on the genealogy, shortcomings and governance aspects of a particular set of indicators. This work provides new insights through a fourfold analysis: (i) an analysis of the context in which transnational legal indicators emerge, (ii) an analysis of their process of commensuration of legal phenomena, (iii) an analysis of their analytical value in jurisprudence and comparative legal studies, and (iv) an analysis of their normative effects on national legal systems.