Board Thread:Warhammer 40k General Discussion/@comment-2.221.112.151-20130917212029/@comment-5.65.81.205-20131001141858

That point seems to change depending on whose writing the story, it started appearing a few years ago and many continue to write as if they can only be collected from the dead.

If you accept the figure of 8-10 sets of impants, but then deduct training losses, implant failure and dead scouts you get (a very rough average) of about 2-3 actual Space Marines per generation. Which would only allow for a very slow rebuilding of a Chapter.