The least dirty currency is the USD, imo. Maybe the Renminbi. They are all dirty. It's a shame too as the world would benefit from a weaker dollar.
Having said that, many smart people lost their fortunes speculating on the dollar direction (disclosure: I have a small speculative basket that probably isn't worth the effort).
Having said that, many smart people lost their fortunes speculating on the dollar direction (disclosure: I have a small speculative basket that probably isn't worth the effort).