When China last week elevated Yi Gang to head the body responsible for its foreign exchange reserves, most attention focused on the gargantuan $2,132bn (€1,499bn, £1,295bn) pile of funds under his agency's management.

But Mr Yi's promotion within the People's Bank of China, the central bank, was important for another reason. A former tenured professor from Indiana University, he is one of the government's most senior "sea turtles" - the term used to describe returnees from overseas study.