Profits, however, may enter more largely into the conditions of production of one commodity than of another, even though there be no difference in the _rate_ of profit between the two employments. The one commodity may be called upon to yield a profit during a longer period of time than the other. The example by which this case is usually illustrated is that of wine. Suppose a quantity of wine and a quantity of cloth, made by equal amounts of labor, and that labor paid at the same rate. The cloth does not improve by keeping; the wine does. Suppose that, to attain the desired quality, the wine requires to be kept five years. The producer or dealer will not keep it, unless at the end of five years he can sell it for as much more than the cloth as amounts to five years’ profit, accumulated at compound interest. The wine and the cloth were made by the same original outlay. Here, then, is a case in which the natural values, relatively to one another, of two commodities, do not conform to their cost of production alone, but to their cost of production _plus_ something else—unless, indeed, for the sake of generality in the expression, we include the profit which the wine-merchant foregoes during the five years, in the cost of production of the wine, looking upon it as a kind of additional outlay, over and above his other advances, for which outlay he must be indemnified at last. Regarding cost of production as the amounts of labor and abstinence required in production, and not as Mr. Mill regards it, as the amounts of wages and profits, the above is simply a case where, in the production of wine, there is a longer _duration of the abstinence_ than in the production of cloth. If there is a free movement of labor and capital between the two industries, they will exchange for each other in proportion to the sacrifices involved; so that the wine would exchange for more of cloth, because there was more sacrifice undergone. The same explanation also holds good in the following illustration: