I think my hairline has been receding since I was around 16 or 17.
The only photo I have to hand from around that time is below. You can see there that the hair on the top of my head is quite thin.
Since then things have gotten gradually worse and worse. I'm now 23 and don't have much more hair than my dad, aged 54. I seem to have inherited the trait from my mother's side of the family, as from all reports both my grandad and uncle had very little hair at my age.
In this photo I was 19, and as you can see my hair is still of a good thickness, but my hairline has receded in to my temples more:
In the photo below I've just turned 22. You can really see how generally absent my hair is:
This one is about a year old, so still 22, but nearer 23. Hairline is going up and over!:
This is the most recent photo I have that makes things visible. Not the best (OK it's a terrible photo), but you can see how my temples are really starting to peak rather than have a rounded top. I don't think my hair as much time left:
The most annoying thing about all of this, is that I don't look all that old, just with the exception of my hair. Unfortunately the hair contributes enough to make me look about 50, rather than 23 or younger
I think my head is too weird a shape to go for the shaven look, so I'll probably engage in some hair restoration surgery at some point.