If a man from a wealthy family background spends six years in college with a trivial income (from a part-time job at the college bookstore, or whatever) and the

If a man from a wealthy family background spends six years in college with a trivial income (from a part-time job at the college bookstore, or whatever) and then lands a well-paid professional job, he has jumped from a low quintile to a high quintile, but is not the sort of "income mobility" that most people hope their children will have access to.