As is clear from the context, and as well-explained by the excellent answers above, the term "relativities" is no more than a code word or a euphemism for "wage disparity," which is currently a hot political issue in the U.S. In the public policy arena, the issue is fairness in worker compensation and the goal is to achieve equity based on skills and productivity and to eliminate outrageous inequality. But the subject of relativities goes beyond that, as companies must also compare their pay scales to those of their competitors in order to attract the bast talents.

It is ideal in translation to translate a one-word term with an equivalent on-word term, but sometimes, strict application of this rule fails to produce a reasonably accessible text. For this reason, I opted for a two-word equivalent, bringing out both the intended meaning of disparity and the core meaning of the source term, "relativities." I hope this makes sense. You can also make it more explicit (and perhaps a tad less faithful to the source text) by using such expressions as:

تفاوتات الأجور
التفاوت في الأجور
التفاوت النسـبي في الأجور
Etc.