There is no division in modern science of goods or services between those which are economic, and those which are not. Their economic significance depends upon their employment in satisfying wants, and not on their inherent qualities. They
must, however, always be related to time and place. Goods of like technical qualities available at different times or in different places must be regarded as different goods, however alike they may be for certain statistical purposes. For instance, tea at import is not the same thing as tea leaving a warehouse for consumption, and the effects of a tax would differ accordingly even if the rate were the same. Arbitrary distinction is usually made between production goods and consumption goods, depending on their remoteness from consumption. A tax on silk cocoons would have different results from a similar rate of tax on silk handkerchiefs. Some goods are complementary to each other; that is, consumption of one is bound up with consumption of the other. Thus tobacco and matches, or whisky and soda are complementary. All these notions are vitally important from the point of view of taxation.