3. _The problem of time-value is involved in repairs and depreciation, and in the use of consumption goods._ It is possible, as we have seen, to increase the sum available for present needs, and to encroach upon the future by postponing repairs on intermediate goods. The balancing of the cost of repairs against the future income is a never-ending task in practical business. One making repairs must purchase the needed materials and labor at a capitalization determined by their expected earning-power in other industries. If the repairs in question will not ensure an annual saving as great as this expected rent, they will not be made. When an industry is declining, it may, for the sake of putting the capital into a better business, be good policy to let the machinery fall into bad repair. The problem of time-value is involved in the application of one's energy to repairing one's own possessions. It is a thought of wide bearings that numberless minor decisions in every petty business involve, if they are correctly made, a measuring of the rate of capitalization. [Sidenote: And in the choice of enjoyments] As will be more fully shown in discussing the relation of the prevailing rate of interest to saving, the recognition of time-value is implied in the use men make of consumption goods, in their postponement of enjoyment, in their storing of goods for future use. The varying gratifications yielded by consumption goods, and their values in different conditions cannot be explained without taking account of differences in time. Wherever there can be a choice in the time at which, and consequently in the conditions under which, a thing can be used, there is a choice presented between the different values. Time-value is present even in a period during which no goods continue to exist, as when a good is consumed at a moment of greater need, to be replaced at a time when less valuable. If an apple is borrowed on the promise to return an apple and a peach at the end of a year, the peach represents the time-difference in value but in the meantime there has been no apple in existence. It is only in a figurative sense that it may be said that interest is paid on that "capital." Interest is paid because of a difference in want-gratifying power, but during the interval there is no material capital. [Sidenote: Prodigality and vice involve a high discount of future happiness]