During the transition phase, great care should be taken in order to avoid that governors of certain NCBs move randomly up and down between certain groups. 2.2.2. Number and Composition of Groups, voting rights, composite indicator and representativeness  •  Two-group versus three-group models. A long debate went on concerning the number of groups and their composition.
Three-group models for the steady state were favoured from the outset, although a two-group model, consisting of 15 and 12 countries was also considered. In the final event, preference was given to a three-group model, which allows, roughly speaking, to rank countries according to whether they are large, medium or small. However, in an intermediary phase a two-group model will be used.