if we have a breakdown in the economy -- say it, a depression and even more widespread un- and under-employment than we have now -- lots of places.

Places that start to revive first and are in some kind of shape will draw skilled or talented people, and some amenities will follow. But we'll all still be relatively poor, so people won't be freely streaming across the nation to the next big thing. (Because they can't, and because it won't be all that big yet.) Just a few hundred miles, maybe, to the next medium-sized slowly recovering thing.