I made a hacky little AppleScript to sort through the birthdates for the 90 of my 784 contacts (11%) where I have record of something. Of those 90 contacts:

• 41 are older than me (45%)
• 4 are the same age as me (5%)
• 44 are younger than me (49%)

So I think that means I am neither old nor young but rather just right.