Hiding little treasures in places other than where it was authored is a small pleasure of S. John Ross; Medieval Demographics Made Easy is one such treasure.
S. John Ross is the creator and author of many things, Risus and Uresia are a couple. Most of these small treasures were either available from or pointed to by the Blue Room. Sadly, the Blue Room no longer exists; long live Rolltop Indigo.
These small treasures are available for those that “find” them. The following file is one such file authored by S. John. If you found it, enjoy.
From the second paragraph:
… a distillation of broad possibilities drawn from several historical reference points, synthesized to a simple tool.
… there’s no way to fantasize wrong … But you may find, as I have, that what follows is a handy springboard from which to dive.