An analysis of official statistics by the Oxford in Berlin research partnership and the Berlin-based WZB Social Science Center found that migration from the United Kingdom to other EU countries rose by 30%, from about 57,000 a year in 2008-2015 to more than 73,000 a year in 2016-2018.

Spain saw the largest number of U.K. arrivals, followed by France.

“These increases in numbers are of a magnitude that you would expect when a country is hit by a major economic or political crisis,” report co-author Daniel Auer said.

Migration among the 27 countries that now remain in the European Union remained relatively stable during the same period, the researchers found.

The number of Britons seeking passports from EU nations also soared by more than 500%. In Germany it was up 2,000%.

British voters opted narrowly in a 2016 referendum to leave the EU, ending the automatic right of the bloc’s citizens to move to the U.K., and of Britons to live and work across Europe. Britain left the EU in January, though it remains bound by the bloc’s rules — including the right to freedom of movement — during a transition period that lasts until the end of 2020.

Brexit has left about 3.6 million EU citizens in the U.K. and more than 1 million Britons in the 27 EU nations scrambling to preserve their residency and employment status. The British government says more than 3 million Europeans have completed a registration process confirming their right to remain in the U.K.

Auer and co-author Daniel Tetlow said the study “reveals the U.K. is facing a potential brain drain of highly-educated British citizens, who have decided to invest their futures in continental Europe.”