On August 15, 1971, the United States of America unilaterally declared of canceling of direct convertibility of its national currency to gold. It finished an epoch of Bretton Woods currency system, US dollar rate started floating and gold turned into independent asset. This event is known in the history as Nixon Shock, because despite of being long-expected, it was a total shock for the most part of countries. The world required several years from then on to develop and launch new rules for international trading.