Medieval Demographics (or, "The Peasants are Revolting")
If you don't know about this, well, you're fucking up. I don't know what to say. This shit (the Domesday book) has been up for a long-ass time, I vaguely remember consulting it regularly when I was running my d20 Cormyr campaign (which was a LONG-ASS TIME ago), and it's sprouted features since then.
What I'm interested in here is "how many people can [x] hexes of arable land being worked at [y] relative efficiency feed?" Domesday Book takes easily-arrived-at figures and gives you projected data on how many settlements the land will support (and of what size), how many fortifications will be required to hold the land, what size standing security force (guards, watch, etc) will be present, and how many of several key professions will be supported by this domain. (It's not ideal, for my purposes, that it uses kilometers, but beggars can't be choosers.) (Pretty sure it says that in the DMG somewhere, at any rate.)
Now, I'm actually using Midkemia Cities to generate my city professions, and there is some assumed demographic info there, and there's some figures from the Wilderlands booklets that have other figures, so I'm still kinda juggling all 3 just to see what feels right. The irony in all of this is that this shit won't matter for quite a while, but once players are at the "worrying about domains" stage of the game, it'll be too late to change all of this crap without serious re-working, and I'm gonna want a clear picture of the situation at the commencement of full-on armies and politics shenanigans.
P.S.: Oh yeah, the map is from Darklands, the best open-ended sandbox RPG set in the Holy Roman Empire that nobody's ever heard of.
P.P.S.: Oh, and here's Michael Bolton as Captain Jack Sparrow.