Mike Mandel dug up some data on trends for workers with advanced degrees. (You want to follow that link to see the charts.)

• "35% of college graduates have an advanced degree. That’s up from 32.7% in 1999."
• "[T]he share of college grads with a doctorate has fallen over the past decade" (to 4.3%).
• "The real earnings for full-time workers with a doctoral degree has dropped by 10% since 1999." (It's increased by 1% for those who quit school after getting a bachelor's.)

Hat tip: Felix Salmon. See his graph of the bimodal income distribution of law school graduates. By the way, since 1999 there's been a 3% decline in mean real earnings of those with professional degrees.