(1) The Law of Returns

In order to investigate the MPP schedule further, let us recall the law of returns, set forth in chapter 1. According to the law of returns, an eternal truth of human action, if the quantity of one factor varies, and the quantities of other factors remain constant, there is a point at which the physical product per factor is at a maximum. Physical product per factor may be termed the average physical product (APP). The law further states that with either a lesser or a greater supply of the factor the APP must be lower. We may diagram a typical APP curve as in Figure 58.