The use of commodity money has been common throughout history. Coins made from precious metals like silver and gold were the standard for thousands of years. By the 18th and 19th centuries, paper currencies began to take hold, although many of them served as promissory notes to pay specific quantities of gold and silver.  Countries like the UK and the US went on to embrace the gold standard, a monetary system tying a standard unit of currency to the value of a certain amount of gold. When the Great Depression and two world wars severely affected the global economy, world leaders created an international monetary system positioning the US dollar as a global currency. International balances were settled in dollars, which were convertible to gold at a fixed exchange rate. The gold standard was in place until 1971, when US President Richard Nixon, faced with surging inflation and high unemployment, ended it as the amount of foreign-held dollars exceeded the amount of gold in the US reserves.