This is the title of a very good article by messrs Dreher, Gassebner and Schaudt ( who looks somewhat like Kenneth Branagh.)
Let me take their entire summary which says 'Stricter immigration and visa policies are a common reaction to terrorist attacks. This column uses historical data from 20 OECD countries to show that while the number of terror attacks increased with the number of foreigners living in a host country, migrants were not more likely to become terrorists than the locals of the country in which they were living. The results also show that bans on Muslim immigration would be more likely to increase the risk of terror than make the domestic population safer.'
Not just very good but essential reading