What is a gold standard?

From, a project of Institute for Humane Studies:

The United States abandoned the gold standard completely in 1974. Professor Lawrence H. White discusses what the gold standard was, why it was abandoned, and whether abandoning it was a good idea. The gold standard meant that currency could be redeemed by banks for gold. The dollar had a set value that it retained. If you went to the bank in the gold-standard era before World War I, for example, you could trade $20.67 at the counter for an ounce of gold. Because the currency was guaranteed in gold, paper money based on gold had a set value. Now that we do not have a gold standard, paper money does not have a set value and the purchasing power of a dollar can fluctuate pretty dramatically. This is called fiat currency.

The gold standard really constrained the federal government, Prof. White says. The obligation to redeem dollars for gold limited money printing at times when the federal government thought printing money might be a good idea. As a result of ending the gold standard, the U.S. Federal Reserve can print as much money as it decides to print. This can be problematic, however, and many countries without a value standard have seen high inflation because of it.

Under our current standard the supply of money is up to the decision of the Federal Open Market Committee. “The fate of the dollar rests with a handful of political appointees,” Prof. White says. Is this a good idea? Is fiat currency a better choice than gold-backed currency? This begs a practical question: Which system better limits inflation? Historically, gold (and silver) standards have dramatically outperformed fiat standards around the world in providing stable, low-inflation currency.