That graph is of course correct, but the question remains, at what level do you centralize? The idea of the EU is that the central point is the EU, and that it

That graph is of course correct, but the question remains, at what level do you centralize? The idea of the EU is that the central point is the EU, and that it is the EU which makes deals with the rest of the blocks. If we follow through with the idea that the ideal level is the nation state, the you have 200 odd countries doing deals with each other. Not very practical. OR, we have several world regions doing deals with each other, plus the UK. Which is a version of "Beggar_thy_neighbour" policy [1]: in a world in which countries in world regions are cooperating with each other by making compromises, there is always the option by one of those countries to play dirty and try to game the system (for example, tax heavens). Note: this applies to big issues. There are things which are better decided at the national, regional or even the city level. [1] https://en.wikipedia.org/wiki/Beggar_thy_neighbour https://en.wikipedia.org/wiki/Beggar_thy_neighbour