Doesn't supply and demand include traders? Like the classic ans to why XXX went up or down today - more buyers than sellers or vice versa?
FX market is HUGE is it not? Isn't the value of FX traded every day multiples of total world GDP or something mind boggling like that? I am sure for every sea shell exporter there is one or more spec traders but in the end, for whatever reason, if there are more USD on offer than are wanted by buyers then down she goes doesn't she?
