<P> When then we say that a person's demand for anything increases, we mean that he will buy more of it than he would before at the same price, and that he will buy as much of it as before at a higher price . </P> <P> Changes in demand is depicted graphically by a shift in the demand curve . On the other hand, "quantity demanded" refers to the quantity of goods consumers want for a given price, conditional on the other determinants . "Changes in quantity demanded" is depicted graphically by a movement along the demand curve . </P> <P> The law of demand was documented as early as 1892 by economist Alfred Marshall . Due to the law's general agreement with observation, economists have come to accept the validity of the law under most situations . Furthermore, researchers found that the success of the law of demand extends to animals such as rats, under laboratory settings . </P> <P> Generally the amount demanded of a good increases with a decrease in price of the good and vice versa . In some cases, however, this may not be true . There are certain goods which do not follow this law . These include (Veblen goods) and Giffen goods . Further exception and details are given in the sections below . </P>

When the term price is used in the law of demand price is referring to