As Crusoe allots more hours of labor to his task, his marginal productivity declines for both of the following reasons:

1. His marginal product—that is, the number of additional coconuts produced in each incremental hour—is declining.

2. At the same time, the subjective value of each one of those additional coconuts is declining (by the law of diminishing marginal utility, pp. 4.4:29-31). The subjective value of the marginal product is his marginal productivity.

While Crusoe's marginal product can be quantified by a cardinal number, his marginal productivity is a kind of subjective value and thus can be assigned only a relative, ordinal ranking. For this reason, no "Marginal Productivity" column is included in the charts on the following pages.