productivity differentials

Again, none of these is because of productivity differentials nor are they the outcome of voluntary choices.

As a consequence of 1, 2, & 3, there is a long-run relationship between productivity differentials and the RER.

Some researchers have tried to use this fact to explain at least part of the observed wage differentials whereby women often earn less than men, even after controlling for observed productivity differentials.

As the Resolution stresses, employment is not just a problem of wage costs, but it is also a problem of wage structures which are well suited to the productivity differentials in each sector of activity.

We could - although Marx does not discuss this in detail (beyond referring to international productivity differentials in the world economy) - also include a fourth case, namely superprofits arising from structural unequal exchange in the world economy.