Penny Napoleonic Wars prompted the use of base metals in 1797. Despite the decimalization of currencies in the United States and, later, throughout the British Commonwealth, the name remains in informal use. No penny is currently formally subdivided, although farthings (¼ d.), halfpennies, and half cents have previously been minted and the mill (1/10¢) remains in use as a unit of account in some contexts. "Penny" is first attested in a 1394 Scots text, a variant of Old English ', a development of numerous variations including ', ', and '. The etymology of the term "penny" is uncertain, although cognates are
Wage unit Wage unit The wage unit is a unit of measurement for monetary quantities introduced by Keynes in his 1936 book "The General Theory of Employment, Interest and Money" ("General Theory"). A value expressed in wage units is equal to its price in money units divided by the wage (in money units) of a man-hour of labour. The classical economists believed that the value of a product could be identified with the number of man-hours of labour which went into its production. This value was inherently real. Economic values can always be expressed in monetary terms except in a barter economy.