Professor William Black:

It is named after an English economist whose dad was the originator of the idea of creating stock exchanges. It is referred to as "Gresham's law" in the economic literature, and it says that bad money drives good money out of circulation in hyper-inflation.

Professor George Akerlof, the Nobel laureate in economics, in his most famous article, "The Market for Lemons," in 1970, used it as a metaphor to describe a Gresham's dynamic in which bad ethics drives good ethics out of the marketplace. This is because, if you gain a competitive advantage by cheating, markets will become perverse and the cheaters will prevail. It also applies to professions, such as appraisers. This is dealt with in the report published by our analogue to you folks, the Financial Crisis Inquiry Commission, and you can read it.