Christians comprise a third of the world's people but half its migrants, according to a report from the Pew Research Centre. They make up three-quarters of foreigners living in America, and 56% in the EU. Jews are the most footloose of all: one in four live outside their country of birth. Only 27% of immigrants are Muslim, who most commonly move to Saudi Arabia or Russia. Migrants favour countries that are both economically vibrant and culturally familiar—fewer tempting destinations may be one reason why Muslims are less inclined than Christians to up sticks.