We often hear that primary metals like copper are going up, so the currencies of producing countries like Australia and Canada should go up, too. Or the price of oil is jumping dramatically, so the yen should fall because Japanese oil importers must buy more dollars to pay for oil, Japan being entirely import dependent.

Are stock markets and currencies correlated? Heres a case: On Jan. 17 Japanese Internet company Livedoor came under investigation for fraud, setting off a downward price spiral that contaminated the entire Tokyo Stock Exchange, which had to close early because it was overwhelmed by orders. The Nikkei 225 stock index fell 5.7 percent in two days.