The hours per week have decreased in the same time from 84 to 66, while the product of the mill in pounds has increased 25 per cent. It may be unnecessary, perhaps, to say that these figures represent the current wages in other mills at the same periods; and that these facts can be sustained by the records of other mills. In its economic effect we must also consider, under efficiency, the whole question of natural advantages of soil, climate, and natural resources. Laborers of the same skill, paid the same real wages, of the same cost, will produce a vastly greater amount of wheat in Dakota than in Vermont or England. This is the chief reason why profits are so high in the United States. In many industries we have very marked natural advantages, which permits a high reward to labor, and yet yields a high profit to the capitalist. This applies not merely to agriculture, but to all the extractive industries, such as the production of petroleum, wood, copper, etc. In short, the whole matter of ease and difficulty of production, of high or low cost of production, taking it in the sense of great or little sacrifice (compare carefully Book III, Chap. II, § 4), comes in under the element of efficiency, in cost of labor. The reader can not be too strongly urged to connect different parts of the economic system together. And the questions of Cost of Labor and Cost of Production are of paramount importance to a proper understanding of political economy. If labor generally became more efficient, without being more highly rewarded; if, without its becoming less efficient, its remuneration fell, no increase taking place in the cost of the articles composing that remuneration; or if those articles became less costly, without the laborers obtaining more of them; in any one of these three cases, profits would rise. If, on the contrary, labor became less efficient (as it might do from diminished bodily vigor in the people, destruction of fixed capital, or deteriorated education); or if the laborer obtained a higher remuneration, without any increased cheapness in the things composing it; or if, without his obtaining more, that which he did obtain became more costly; profits, in all these cases, would suffer a diminution. And there is no other combination of circumstances in which the general rate of profit of a country, in all employments indifferently, can either fall or rise.