需要と供給
For almost all products, the demand curve has a negative slope: as the price increases, demand for the good decreases. (See Supply and demand for background.) Giffen goods are an exception to this general rule. Unlike other goods or services, the price point at which supply and demand meet results in higher prices and greater demand whenever market forces recognize a change in supply and demand for Giffen goods. As a result, when price goes up, the quantity demanded also goes up. To be a true Giffen good, the good's price must be the only thing that changes to produce a change in quantity demanded. A Giffen good should not be confused with products bought as status symbols or for conspicuous consumption (Veblen goods), although there may be some overlap as consumers are more likely to engage in conspicuous consumption as a way to engage in "aspirational spending" as a way to increase their social status.