The broadest principle of value
3. The law of diminishing returns is the broadest principle of value. The one character common to all goods is that their importance varies with their quantity in any given connection. This is true of direct goods whose power to gratify wants falls as the supply grows; it is true of indirect goods, whose technical importance diminishes as the quantity increases, and which when taken at any given cost can be applied, after a point, only with diminishing advantage. The gradual extension of the marginal principle from land used in agriculture to every conceivable economic agent is the most important development of the last century of economic theory.
Generality of the law of value
It being true that things are measured by the utility of the unit used last, logically considered, the least change in the combination alters the value of all the factors. Practical economic problems, therefore, are dynamic, not static. The view that the shares of the different factors are fixed by quite separate laws has not been accepted here. The law of rent is the same as the law of wages in its essential point and principle. It is a general law of value applied to a particular kind of want-gratifier. The law of substitution likewise is a general law, for within limits some substitution of factors is always possible along the margin. That being true, every movement of price creates its own resistance; substitutes will be found for materials, demand will decline, and a new equilibrium of price will be attained.
Mutual employment of the factors
An ever changing problem
4. The factors and agents of production mutually furnish the field of employment for each other. Each factor is dependent for its technical efficiency on the presence of the other factors. If labor is plentiful and machines are scarce, machines bear a high rent. In accordance with the law of diminishing returns, the last unit of labor in that case contributes little to the product, and labor gets low wages, while more is attributed to the machine. Each machine thus may be considered to offer a field for the employment of labor. If population increases and land remains fixed, the need for food raises the rental value of land. But if population increases slowly, and capital and science progress, the field for the employment of labor is enlarged; and if new lands are opened up or new resources are discovered beneath the surface of the land, the field for labor is still more enlarged and a greater share is attributed to labor. This changing character of the problem must be recognized; no share is foreordained in size.
The pursuit of the analysis of value along the lines of marginal utility thus leads to conclusions far less mechanical, and, to the superficial student, less simple than were the doctrines prevailing in the older economics. But the conclusions are, let us hope, more exact and more applicable to the real world, enabling the student to arrive at juster views of the present interests and of the future welfare of society.