i was talking to a guy from travelex the other day about this and this was his explanation.
its called "carry money"
basically the money that people borrow from say a japan (low interest rates) and then invests it in a relatively interest rate environment like Australia, NZ or Norway, so you borrow at say 1% and invest at say 5.5% , thats not much on piddly amounts but if you do this on say a billion (and he estimated that the carry trade was worth 3 trillion bucks) it pushes a currency up ie like aud and nzd, however when uncertainty occurs people pis s their pants and pull the "carry" money out back to its origin, hence yen goes back up and aud and nzd go down............
