Is state-level GDP per capita the correct model to use? Why not compare, for example, city-level GDP per capita? After all capital and workforce are free to move between cities not just countries.
(Plus the whole fun where American member states are not entirely sovereign, while EU member states are countries in their own right, and in the case of e.g. Germany are themselves federal nations with multiple constituent states)
Well yes. And I don't really understand why a common currency between rich and poor countries is a problem. But people are saying that it won't work. I suppose it won't work if you depend on the government to be able to control the money supply to fool people into thinking they have more or less money than they really do. But is that really necessary?
(Plus the whole fun where American member states are not entirely sovereign, while EU member states are countries in their own right, and in the case of e.g. Germany are themselves federal nations with multiple constituent states)