think about this, the average interest in the u.s from 1990-2007 was about let say 4% and japan stayed at zero hoping to depreciate against the dollar. But, didnt happen because their advanced technology (product) became/becomes the most advanced country in the world keeping the yen higher against the dollar. Because Japan was the 2nd largest economy in the world before 2010, could it be investors are using yen to hedge or pay yen to buy gold. Its all about maximizing profit.