Clarifying:

    1) The best years of a Stanford Undergrad's life are still ahead.
    2) The best years of 20 somethings's lives are still ahead based
    on analysis  that never mentions things like how typical wage
    earners are supposed pair off and start families in a 4 income economy.

The evidence for this comes from comparing 20-somethings to older populations. The olders are happier so the 20 somethings will be too. Which totally ignores the opportunities that disappeared wholesale between these generations.