You are missing the point: when wages are negotiated by power, productivity is a secondary goal if any. As soon as productivity departs wages, you will see it

You are missing the point: when wages are negotiated by power, productivity is a secondary goal if any. As soon as productivity departs wages, you will see it go to any direction, and most likely, down. And if productivity goes down, you better be damn sure wages are going down as well. > Should the company be able to fire you after 20 years because someone new might be more productive? That will be desired if by union negotiation you are forced to pay both equally. But if you allow for different wages that can be re-negotiated at any point.