雅思阅读材料：The Magic of Diasporas

　　Diasporas also help spread ideas. Many of the emerging world’s brightest minds are educated at Western universities. An increasing number go home, taking with them both knowledge and contacts. Indian computer scientists in Bangalore bounce ideas constantly off their Indian friends in Silicon Valley. China’s technology industry is dominated by "sea turtles" (Chinese who have lived abroad and returned).

　　Diasporas spread money, too. Migrants into rich countries not only send cash to their families; they also help companies in their host country operate in their home country. A Harvard Business School study shows that American companies that employ lots of ethnic Chinese people find it much easier to set up in China without a joint venture with a local firm.

　　Such arguments are unlikely to make much headway against hostility towards immigrants in rich countries. Fury against foreigners is usually based on two (mutually incompatible) notions: that because so many migrants claim welfare they are a drain on the public purse; and that because they are prepared to work harder for less pay they will depress the wages of those at the bottom of the pile.

　　The first is usually not true (in Britain, for instance, immigrants claim benefits less than indigenous people do), and the second is hard to establish either way. Some studies do indeed suggest that competition from unskilled immigrants depresses the wages of unskilled locals. But others find this effect to be small or non-existent.

　　Nor is it possible to establish the impact of migration on overall growth. The sums are simply too difficult. Yet there are good reasons for believing that it is likely to be positive. Migrants tend to be hard-working and innovative. That spurs productivity and company formation. A recent study carried out by Duke University showed that, while immigrants make up an eighth of America’s population, they founded a quarter of the country’s technology and engineering firms. And, by linking the West with emerging markets, diasporas help rich countries to plug into fast-growing economies.

　　Rich countries are thus likely to benefit from looser immigration policy; and fears that poor countries will suffer as a result of a "brain drain" are overblown. The prospect of working abroad spurs more people to acquire valuable skills, and not all subsequently emigrate. Skilled migrants send money home, and they often return to set up new businesses. One study found that unless they lose more than 20% of their university graduates, the brain drain makes poor countries richer.