The benefit of investment involves market and money, a certain level of which can be measured by the difference of income between the laborer at this level of education and that at the next.

• 投资性收益是一种市场化的、货币性收益，某一级教育的投资性收益的衡量，可以用接受这一级教育的劳动者的工资收入与接受下一级教育的劳动者的工资收入的差额来计算。