... the net flow of which reversed several decades ago. For the past 30 years, many American cities (the nice ones with living economies, think NYC, SF, Boston, Portland, Austin, etc) have been experiencing a steady influx of affluent white people, replacing the ones who fled a generation before.

Hence all the hand-wringing over "gentrification".

Really, this is just a return to the long-term normal of cities. Cities are centers of power and wealth. It was a weird American aberration that, for a time, "inner city" was associated with poverty and decay.