COMPLEMENT-IN-CONSUMPTION: One of two goods that are consumed together to provide satisfaction -- that is, the goods are used jointly to satisfy wants and needs. A complement good is one of two alternatives falling within the other prices determinant of demand. The other is a substitute good. An increase in the price of one complement good causes a decrease in demand for the other. A complement good has a negative cross price elasticity. When the terms complements or complement goods are used, they typically means complement-in-consumption (compare this with complement-in-production). Examples of complement goods are golf clubs and golf balls; hamburgers and french fries; and cars and gasoline. In each case, the two goods "go together." People seldom use or consume one without the other.
