So we get back, in the end, to the proposition with which we started, that the purpose of economic activity and organization is to supply human needs. Where the need is felt, the demand arises. When the demand arises, the agencies of supply, namely production and distribution, usually respond. One of the great tasks of economic organization, therefore, is to estimate the probable demand and so influence production and distribution that the supply will neither be excessive nor fall short. If there is an over-supply of any commodity, prices normally will fall. That means that goods may bring less than it costs to produce and to distribute them. One reason for the organization of industry on a large scale under great corporations is that supply can thus be kept closer to demand. At any rate the consumer, by his greater or smaller demand, virtually determines all activities of production and distribution. He is the pivot of the whole economic system. [Sidenote: The factors in demand.] Whether the demand on the part of the consumer will be larger or smaller depends on three factors. The first is the utility of the goods to him. Economic goods do not have the same utility to all men at all times. The utility of ice on a warm summer day may be considerable; in midwinter it is next to nothing. The utility of eye-glasses to short-sighted men is great; to men of normal sight they have no utility at all. Economic goods may, therefore have a greater or smaller utility depending upon the place, the time, and the consumer. Bear in mind, moreover, that each consumer matches the utility of one commodity with the utility of other commodities which he finds available, and his demand follows the direction of the greater utility. A second factor in demand is the price of the goods. When the price goes up, the demand ordinarily will go down, because some customers will decide that the utility of their money is greater than that of the goods at the increased price. Finally, demand depends in part upon the purchasing power or wealth of the consumers. In prosperous times, when people have plenty of income, the utility of goods seems greater than the utility of money; in times of depression and low incomes the reverse is true. The interaction of these three factors determines the demand. [Sidenote: What production means.]