When there are two forms of money used in trade , and the government forces them both to trade for the same value , if people desire one ( `` good '' money ) more than the other ( `` bad '' money ) , they will always offer the bad money in trade before the good money . Over time , the good money will be kept in pocket , and only the bad money will be found in the market .
However , if not given the choice , and required to accept all money , good and bad , they will tend to keep the money of greater perceived value in their possession , and pass on the bad money to someone else .