Seems like Richard Florida should say something about this, right? Maybe he did and I just missed it.
"Indeed, the trend has appeared to continue. Between 2005 and 2007, only eight metropolitan areas -- many of them bigger -- added more college-educated migrants of any age than did Portland, the nation's 23rd largest metro area, according to an analysis of Census data by William H. Frey, a demographer at the Brookings Institution. A more detailed breakdown by age isn't yet available, but Mr. Frey and other demographers say the bulk of the movers are likely between the ages of 25 and 39, the most mobile age group by far."