Care to elaborate? When they say college graduates earn more, at least for anything I've ever read, it is based on mean income. Due to the way mean is calculated, and incomes tending to follow the power law, the top 1% are going to be the ones who have the largest representation of that higher average income.

As such, degree holders may simply earn more because they are overly represented in supply managed industries with artificial incomes, like the aforementioned doctor.