 At the end of 2006, approximately 70 percent of the reserves were in U.S. dollar assets, 20 per cent in euros and 10 per cent in other currencies, according to economist Brad Setser.Most of China's currency reserves are invested in high grade U.S.-dollar-denominated debt, such as U.S. Treasuries, though as early as 2007 it was estimated that SAFE held $100 billion worth of U.S. mortgage-backed securities, hoping to achieve higher returns than those on U.S.