Intriguingly, the more educated Americans become, the more insular they are. (Hence Mr Miller's confusion.) Better-educated people tend to be richer, so they have more choice about where they live. And they are more mobile. One study that covered most of the 1980s and 1990s found that 45% of young Americans with a college degree moved state within five years of graduating, whereas only 19% of those with only a high-school education did.
As I've often quipped, don't send your children to college if you want them to stay. I mean that sarcastically. Of course, being a parent myself, I wouldn't ask any family to deny their children the benefits of a college education. But attempting to impede talent from out-migrating is almost as bad as not helping young adults attend university.
Addressing the issue of the article, the Creative Class isn't seeking diversity. City living can be just as segregated as the suburbs. We seem to be witnessing a new version of White Flight, with ideology replacing race as the primary push factor. The one constant is that domestic migration continues to be a rather sordid affair.