Immigrant networks are a rare bright spark in the world economy. Rich countries should welcome them

　　THIS is not a good time to be foreign. Anti-immigrant parties are gaining ground in Europe. Britain has been fretting this week over lapses in its border controls. In America Barack Obama has failed to deliver the immigration reform he promised , and Republican presidential candidates would rather electrify the border fence with Mexico than educate the children of illegal aliens. America educates foreign scientists in its universities and then expels them, a policy the mayor of New York calls "national suicide".

　　This illiberal turn in attitudes to migration is no surprise. It is the result of cyclical economic gloom combined with a secular rise in pressure on rich countries’ borders. But governments now weighing up whether or not to try to slam the door should consider another factor: the growing economic importance of diasporas, and the contribution they can make to a country’s economic growth.

　　Old networks, new communications

　　Diaspora networks—of Huguenots, Scots, Jews and many others—have always been a potent economic force, but the cheapness and ease of modern travel has made them larger and more numerous than ever before. There are now 215m first-generation migrants around the world: that’s 3% of the world’s population. If they were a nation, it would be a little larger than Brazil. There are more Chinese people living outside China than there are French people in France. Some 22m Indians are scattered all over the globe. Small concentrations of ethnic and linguistic groups have always been found in surprising places—Lebanese in west Africa, Japanese in Brazil and Welsh in Patagonia, for instance—but they have been joined by newer ones, such as west Africans in southern China.