U. S. President, Richard Nixon is credited with ending the Bretton Woods Accord and fixed rates of exchange, eventually resulting in a free-floating currency system. After the Accord ended in 1971, the Smithsonian Agreement allowed rates to fluctuate by up to ±2%. In 1961–62, the volume of foreign operations by the U. S. Federal Reserve was relatively low. Those involved in controlling exchange rates found the boundaries of the Agreement were not realistic and so ceased this[clarification in March 1973, when sometime afterward[clarification none of the major currencies were maintained with a capacity for conversion to gold,[clarification organizations relied instead on reserves of currency. From 1970 to 1973, the volume of trading in the market increased three-fold. At some time (according to Gandolfo during February–March 1973) some of the markets were "split", and a two-tier currency market[clarification was subsequently introduced, with dual currency rates. This was abolished in March 1974.