Why should I care that this has happened?
Well, the most paranoid alarmists worry that Brexit will trigger a Frexit, which could trigger a Germexit, until the whole EU framework falls apart; and then the combination of slow-growth and ascendant right-wing nationalism could lead to the kind of zero-sum thinking that made Europe a charnel house for much of the 20th century. For all its faults, there’ve been no world wars since the EU was formed.

More immediately (and certainly), Brexit will hurt European economic growth, and that could be a weight on the whole global economy