My simple model is that the world is segregating along the dimension of IQ more than before. (Or is that IQ/conscientiousness? Some other bundle? Probably so.) That includes more IQ-based segregation across firms, across cities, across marriages, and so on. You see this in the productivity data, namely that top firms are doing pretty well on the cutting edge, and most other firms are lagging behind, with a greater innovation diffusion gap than before. Most of the rise in inequality has been across firms, rather than within firms.
This increasing segregation is happening because it is a privately efficient way to run O-Ring production, although you might dispute whether it is also socially efficient, given the drain of talent from the middle and the bottom end.
The more there is segregation by IQ, the more likely you will find feasible and indeed desirable mixing across many other variables. Including age. Color of hair too. Length of fingernails. And so on.
For a conversation related to this point, I thank B.