ABSTRACT
W hen a small percentage alteration in price causes a large percentage alteration in the amount of a commodity which is sold, the demand for that commodity is said to be elastic. By speaking of a percentage or proportionate alteration we are enabled to compare the elasticity of the demands for any two commodities however much they may differ in the measure by which they are sold or in price. We can, if we wish, compare the elasticity of the demand for coal which is sold by the ton with that for gas which is sold by the cubic foot, or the demand for the cheapest beer with that for the most expensive champagne.
