Marshall's Neo-Classical Labor-Values

With the coming of marginal utility theory, the economists of the late nineteenth century were left with a theory of exchange values, but not with a theory of value. For example, William Stanley Jevons suggested that the concept of value be dropped from economics, leaving behind only vectors of exchange ratios (Jevons 1879). Not a few general equilibrium economists today hold much the same view. However, then, as today, there were seemingly fundamental economic questions that required a more general concept of value. Whenever economists turned to describing the movements in the economy over time or comparing the economies of different countries, they inevitably wanted to make statements about changes or differences in the real value of goods.