In the Middle Ages, when money consisted primarily of coins, silver and gold coins circulated simultaneously. As governments came increasingly to take over the coinage and especially as fiduciary money was introduced, they specified their nominal (face value) monetary units in terms of fixed weights of either silver or gold. Some adopted a national bimetallic standard, with fixed weights for both gold and silver based on their relative values on a given date—for example, 15 ounces of silver equal 1 ounce of gold (see bimetallism). As the prices changed, the phenomenon associated with Gresham’s law assured that the bimetallic standard degenerated into a monometallic standard. If, for example, the quantity of silver designated as the monetary equivalent of 1 ounce of gold (15 to 1) was less than the quantity that could be purchased in the market for 1 ounce of gold (say 16 to 1), no one would bring gold to be coined. Holders of gold could instead profit by buying silver in the market, receiving 16 ounces for each ounce of gold; they would then take 15 ounces of silver to the mint to be coined and accept payment in gold.

Continuing this profitable exchange drained gold from the mint, leaving the mint with silver coinage. In this example silver, the cheaper metal in the market, “drove out” gold and became the standard. This happened in most of the countries of Europe, so that by the early 19th century all were effectively on a silver standard. In Britain, on the other hand, the ratio established in the 18th century on the advice of Sir Isaac Newton, then serving as master of the mint, overvalued gold and therefore led to an effective gold standard. In the United States a ratio of 15 ounces of silver to 1 ounce of gold was set in 1792. This ratio overvalued silver, so silver became the standard. Then in 1834 the ratio was altered to 16 to 1, which overvalued gold, so gold again became the standard.

The great gold discoveries in California and Australia in the 1840s and ’50s produced a temporary decline in the value of gold in terms of silver. This price change, plus the dominance of Britain in international finance, led to a widespread shift from a silver standard to a gold standard. Germany adopted gold as its standard in 1871–73, the Latin Monetary Union (France, Italy, Belgium, Switzerland) did so in 1873–74, and the Scandinavian Union (Denmark, Norway, and Sweden) and the Netherlands followed in 1875–76. By the final decades of the century, silver remained dominant only in the Far East (China, in particular). Elsewhere the gold standard reigned. (See also Free Silver Movement.)

The early 20th century was the great era of the international gold standard. Gold coins circulated in most of the world; paper money, whether issued by private banks or by governments, was convertible on demand into gold coins or gold bullion at an official price (with perhaps the addition of a small fee), while bank deposits were convertible into either gold coin or paper currency that was itself convertible into gold. In a few countries a minor variant prevailed—the so-called gold exchange standard, under which a country’s reserves included not only gold but also currencies of other countries that were convertible into gold. Currencies were exchanged at a fixed price into the currency of another country (usually the British pound sterling) that was itself convertible into gold.

The prevalence of the gold standard meant that there was, in effect, a single world money called by different names in different countries. A U.S. dollar, for example, was defined as 23.22 grains of pure gold (25.8 grains of gold 9/10 fine). A British pound sterling was defined as 113.00 grains of pure gold (123.274 grains of gold 11/12 fine). Accordingly, 1 British pound equaled 4.8665 U.S. dollars (113.00/23.22) at the official parity. The actual exchange rate could deviate from this value only by an amount that corresponded to the cost of shipping gold. If the price of the pound sterling in terms of dollars greatly exceeded this parity price in the foreign exchange market, someone in New York City who had a debt to pay in London might find that, rather than buying the needed pounds on the market, it was cheaper to get gold for dollars at a bank or from the U.S. subtreasury, ship the gold to London, and get pounds for the gold from the Bank of England. The potential for such an exchange set an upper limit to the exchange rate. Similarly, the cost of shipping gold from Britain to the United States set a lower limit. These limits were known as the gold points.

Under such an international gold standard, the quantity of money in each country was determined by an adjustment process known as the price-specie-flow adjustment mechanism. This process, analyzed by 18th- and 19th-century economists such as David Hume, John Stuart Mill, and Henry Thornton, occurred as follows: a rise in a particular country’s quantity of money would tend to raise prices in that country relative to prices in other countries. This rise in prices would consequently discourage exports while encouraging imports. The decreased supply of foreign currency (from the sale of fewer exports) plus the increased demand for foreign currency (to pay for imports) would tend to raise the price of foreign currency in terms of domestic currency. As soon as this price hit the upper gold point, gold would be shipped out of the country to other countries. The decline in the amount of gold would produce in turn a reduction in the total amount of money, because banks and government institutions, seeing their gold reserves decline, would want to protect themselves against further demands by reducing the claims against gold that were outstanding. This would tend to lower prices at home. The influx of gold abroad would have the opposite effect, increasing the quantity of money there and raising prices. These adjustments would continue until the gold flow ceased or was reversed.

Precisely the same mechanism operates within a unified currency area. That mechanism determines how much money there is in Illinois compared with how much there is in other U.S. states or how much there is in Wales compared with how much there is in other parts of the United Kingdom. Because the gold standard was so prevalent in the early 20th century, most of the commercial world operated as a unified currency area. One advantage of such widespread adherence to the gold standard was its ability to limit a national government’s power to engage in irresponsible monetary expansion. This was also its great disadvantage. In an era of big government and of full-employment policies, a real gold standard would tie the hands of governments in one of the most important areas of policy—that of monetary policy.