The regime of floating currencies ushered in by the breakdown of the Bretton Woods agreement and symbolized by President Nixon’s decision to sever the dollars peg to gold turns 35 years old on Aug. 15, 2006.

Despite their current prevalence, floating exchange rates are nearly unprecedented in the past half-millennium of capitalism and, as various officials including former Federal Reserve Chairman Alan Greenspan have pointed out, predicting their movement is a rogues game. At best, forecasting currency movements is a Herculean task. At worst, it is a Sysiphusian occupation. Nonetheless, given the importance of currency movements for businesses, investors, and speculators, many people have little choice but to make the effort.