No one can say how much reward any work at any time "fairness" is worth,
No one can "prove" that wage levels for various activities in this or that relative relationship to each other would have.
So there is no way to prove factual, objectively and scientifically, that a stenographer in 1970 in Munich, in the sense of a just determination of salaries between 800 and 1200, - DM has to make, an engineer, depending on power 1500, - to 2000, - DM.
There are no more objective reference points that would say that a construction worker in 1500, - DM must make monthly, if a degree in economics at the same time, 1300, - DM earned.
If you look at this basic situation lead in mind, one might despair of the job evaluation at all.
However, in business, the practice has yet to answer the question just how different the various activities and work performance should be rewarded, especially what steps are to be elected at the multitude of different jobs.
Source: "Goossens Personnel Manager's Guide," page 351
Many job evaluation methods and procedures in the past and today are pseudo-sciences!