The mobility those regions demonstrate is better than average for all income classes, and those income classes are defined nationally, not locally. Of course,

The mobility those regions demonstrate is better than average for all income classes, and those income classes are defined nationally, not locally. Of course, that "gotta get out of here" feeling isn't limited to lower income kids, so it could be a factor. Certainly it's typically good for your earnings if you're willing to move where you can make more money. But then why isn't upstate New York dark blue? (Sorry, upstate New York!)