The Economist writes,
For all its current economic woes, America remains a beacon of entrepreneurialism. Between 1996 and 2004 an average of 550,000 small businesses were created every month. One factor is a fairly open immigration policy. Vivek Wadhwa of Duke University notes that 52% of Silicon Valley start-ups were founded by immigrants, up from around a quarter ten years ago. But since 2001 the threat of terrorism and rising xenophobia has made immigration harder. Today more than 1m people are waiting to be granted legal status as permanent residents. Yet only 85,000 visas a year are allocated to the sort of skilled workers that might go on to found successful businesses of their own.