1. A method comprising listing for trading on an exchange a foreign currencies indexed financial instrument having a composition calculated by the method comprising: (i) receiving at an exchange computer system exchange rates for a group of foreign currencies; (ii) receiving competitive weights for each of the foreign currencies such that each weight reflects competition between the goods of the United States and a country corresponding to the foreign currency in the markets of third countries as well as foreign currency trading patterns in international foreign exchange markets; and (iii) calculating by a computer processor a geometric average of the exchange rates with corresponding competitive weights; (iv) multiplying the geometric average by a multiplier; (v) calculating a new multiplier when the competitive weights are changed, wherein (v) comprises using the formula B t = B t - 1 ÷ ∏ i = 1 7 ⁢ ⁢ ( 1 / S i , t ) w i , t ∏ i = 1 7 ⁢ ⁢ ( 1 / S i , t ) w i , t - 1 where S it is the exchange rate of currency i at time t, expressed in dollars per unit of foreign currency, w i,t is the weight of currency i at time t, B t is the new multiplier and B t−1 is the previous multiplier.