Not necessarily. You could, for example, have a large generation (the Boomers) pass through their peak earnings years at the same time as a large number of low-

Not necessarily. You could, for example, have a large generation (the Boomers) pass through their peak earnings years at the same time as a large number of low-skill immigrants arrive in search of a better life. That wouldn't be polarization in the sense of the middle being split into rich and poor, it would just be changing demographics. No idea if that's what's actually happening, but just watching the dot of the median and not the whole distribution is not likely to be enlightening unless events conspire to keep the shape of that distribution static. I don't think that's the case.