Outsiders, like me, who are trying to understand how much immigration is driving the “Brexit” debate about the European Union might consider this fact: Britons are much more likely today to encounter people born in another country — both inside and outside Europe — than they were a decade ago.

In 2014, about 1 in 8 people residents were born outside the U.K. — up from about 1 in 11 a decade earlier, according to government statistics.