The role of central government is somewhat “minor” in federal countries that transferred most water competences to sub-national governments such as the United States (Box 5.1) or Belgium, where water responsibilities are so scattered across states or regions that it is almost impossible to capture a “national institutional mapping”. This indicator helps “measure” the fragmentation of roles and responsibilities, based on the assumption that the more actors there are, the more “complex” the situation is. But it has to be analysed in light of the governance tools adopted to overcome such complexity.