Gresham's law

Observation that “bad money drives out good.” It is named for Sir Thomas Gresham (1519–1579), financial agent of Queen Elizabeth I, who was one of the first to elucidate it (he had been preceded by Copernicus). The meaning expressed is that, if two coins have the same face value but are made from metals of unequal value, the cheaper will tend to drive the other out of circulation; the more valuable coin will be hoarded or used for foreign exchange instead of for domestic transactions.

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