My central objective in writing this paper (“On the Very Idea of a Just Wage”) was to respond to the reappearance of what Paul Krugman has referred to, somewhat abusively, as a “cockroach idea.” The thing about cockroaches is that, no matter how many times you kill them, they keep coming back. Similarly, there are some ideas that, no matter how many times they may be refuted, nevertheless keep reappearing, or get “rediscovered” by people who consider them fresh insights.
The idea that the marginal productivity of labour represents the “contribution” that an individual worker makes to production is a cockroach idea in this sense. It is something that many people would like to believe, because it implies that the natural tendency of markets will be to set wages at a level that corresponds to an intuitively plausible principle of distributive justice (i.e. “to each according to his or her contribution”). It was, however, intensively debated in the early 20th century and rather decisively rejected.