Percentage of HS graduates who die before reaching 50?

I recently found a rather mercenary * ( site where my former highscool classmates seem to have congregated.

It was not a huge school, I think there were 175 or so in my graduating class. Extrapolating from the dozen or so reports (assuming some underreporting) it looks like around 10% of my class of 1980 has died! WTF?

Could somebody please point me in the direction of some data (or just search terms) that would tell me if this is normal, or if not, how excessive is it?

*They are subscription based, and censor URLs and email addresses from thier forum postings and even PMs.