I don't have the exact figure re retirements as I took early retirement in August. The boss said that he's expecting more in the coming years as folks hit 65. What's harder to quantify is the number of early retirements (from 60yo) and part time. Anecdotally, I'd say there's about 1 a month.
20 years ago there was a big hiring boom from 2004-2006/7. Most of us were around 35-40 years old.