> My working hypothesis is that people in general want to live in California like places, if they can afford it.

This is my general thinking as well, and it happens to fit with my current life experience.

I'm unconvinced that there has been, generally speaking, a fundamental change in the preferred environment people wish to live in; instead it seems more likely that traditionally popular American urban areas are just too expensive and offer relatively little (compared to other parts of the world) in terms of services to justify living there... Even for those that might otherwise choose to.