Answer: cultural diversity has its positive impact only if there is democracy, i.e. free movement of goods, ideas, people. If there is this freedom, then Europe is an extremely creative, free and progressive place. Europeans experienced times of nationalism, wars, revolutions so Europe in itself is not a guarantee of creativity, freedom and progressive thinking, but if there is a population able to establish really "European lifestyle" than diversity can have unique consequences.
Explanation: usually there is a tendency to supress differentness, but Europe experiences the worst consequences of such tendency so there is some sort of notion that diversity is creative and productive and that it is worth of taking care of. Impact ? Populations speaking different languages. educated, flexible, able to work with advanced technologies, psychologically open, accostumed to "different" things, able to travel to distant places and learn.
