The analysis in this chapter assumes that the typical production process eventually is subject to diminishing returns to the variable input. The same principle applies to production analysis using isoquants. Figure 11 illustrates the diminishing marginal physical product of labor when the amounts of other resources are held constant. In Panel A of Figure 11, capital is held constant at 3 units. Points a through h represent the amounts of labor needed to produce output levels ranging from 2,000 to 20,500 units. In Panel B, the total product curve is derived from Panel A when capital is fixed at 3 units, and shows diminishing returns to labor. As we add more and more labor to a fixed stock of capital, the increased output from hiring additional labor eventually falls.