Monday, November 15, 2021

Demographics Quick Rule-of-Thumb

I was thinking again about medieval demographics the other day. This follows on an earlier summary article I wrote here

Thing is, I was trying to do some large-scale number crunching in my head, and found that I got a little tangled up about it. So in response, I came with a very rough rule-of-thumb based on units in powers of 10 that I could mentally juggle, and is roughly on the right order with what we know of medieval European societies. Here it is:

Medieval demographics rule-of-thumb

So in the grand total, that represents a 4-million population that might be an entire country on its own, or something. For example, England fluctuated from about half this population size, to the full unit, and back again (between the Dark Ages and the Black Death). On the lower end, recall that for a medieval village, it's pretty accurate to roll 1d6 × 100 for the population (giving an average of 350 each).

How much land space would this total organization take up? Well, that depends, because (much like the English example) population density varied a lot over the medieval period, and besides that we only have estimates anyway. A few possibilities:

  • 10 people/mi² -- Polity takes 400K mi² (600 × 600 miles); the lowest density estimate anyone's proposed for the Dark Ages in Europe.
  • 20 people/mi² -- Polity takes 200K mi² (450 × 450 miles); a more common estimate for Dark Ages population density.
  • 40 people/mi² -- Polity takes 100K mi² (300 × 300 miles); density of England at its low point, start and end of the middle ages. 
  • 80 people/mi² -- Polity takes 50K mi² (200 × 200 miles); density of England at its high point, middle of the medieval period, and matching its actual land area. 

Now -- that's a lot of real-world content. It's likely that you certainly don't want to detail quite that much stuff in your campaign world. As I've noted before, an obvious reasonable method is to just abstract away all the stuff below a particular map level that you're using. (For example, if you use low-England density and a 30-mile hex map, then your country might take up about 10 ×10 hexes; so you could explicitly place the capital and 10 cities, but just hand-wave, without drawing anything, the fact that most every such hex has its own town, 10 castles, and 100 villages). Alternatively, fantasy writers seem to have a tradition of much lower densities than ever occurred in reality, so you can feel free to follow suit.

So anyway, that gives me a couple of simple, memorable numbers I can remember when I'm doing mental estimates for this kind of thing. Is it helpful to others?

20 comments:

  1. I always like numbers like this because it points out how much we vastly underestimate population and by extension the reach of "authority" in D&D. And by authority I mean law, taxes, and the pressure of social standing.

    I assume 10 castles in a 30-mile hex would mean 10 family-banners who claim ownership over most of the land, so when PCs pull 2000 GP out of some dungeon, someone is going to come looking for that money.

    I bet thought the clustering of civilization is important too. The villages would radiate from the town and castles so there could be swaths of untouched wilderness were the wild things are.

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    1. Right, I agree with all that!

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    2. "10 castles in a 30-mile hex" - actual medieval borderland areas like western Aberdeenshire do tend to have about that number. A lot of the 'castles' are towers/brochs though, not big castles like Kildrummy, or even mid-size like Huntly castle. 2-4 substantial castles seems likelier to me, plus a lot of fortified manor houses, towers/brochs etc.

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  2. For me, this sort of thing is useful. For others, I'd say there's a whole lot of "It depends..." .

    The % Urban seems to be high to me. 13% might have been the number in 1300 but certainly not in 900. It depends on what century of the medieval period you want to model.

    Between the Justinian Plague in 536 and about 950 western Europe had very few cities of any size. I don't have the estimates handy but it was very low. Less than 10% of the population was urban but maybe much lower than that.

    You might look at Adventurer Conqueror King for comparison to your table. ACKS has a procedure and tables for this sort of thing in the campaign creation portion of the core rules book. I'm aware a lot people don't like Alex or play his game so YMMV on that suggestion.

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    1. You're right.

      But, if we're talking about 900, then we're also not talking about longswords, plate armours, crossbows (at least in the style we usually think of them)… these are all things of the late medieval / early renaissance period.

      These numbers are a "quick rule of thumb", they're just orders of magnitude. As such, they seem pretty excellent. Just make those capital and cities smaller to adjust for earlier ages or different areas.

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    2. I agree with both of you here; definitely I've heard 10% urbanization as a rule of thumb, possibly less. Being able to remember the order-of-10 values mentally is really what I'm looking for. The 13% number was computed just to see if I was crazy off; if it got as high as 20% then I'd look to fix something.

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  3. Good stuff! Like anything else, the numbers can be tweaked to fit a campaign, but it's good to have numbers like this.

    Now can you pls go find a nice, fun, quick siege resolution engine, pls? :D

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    1. By fun coincidence, the ACOUP blog is running a series on fortifications and sieges right now. The first and second posts are up, and he's planning it as a series of five.

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    2. Wow, that looks very impressive. Thanks for that!

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  4. Do those numbers for population density include the areas of unpopulated spaces — swamps, mountain ridges, deep forests, etc?

    That is, is the rural countryside much denser than those figures (compensating for the unpopulated wasteland), or are they density of populated areas?

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    1. Yeah, to my understanding those (scholarly) density figure estimates are for the entirety of the European continent. So the more you zoom in fractally where the people are, the denser it should get.

      Some of those I got from Wikipedia: Demography of England; others from Gies, Life in a Medieval Village, citing Chapelot and Fossier.

      Also my double-check versus England involved me dividing the middle-ages population by the entire land area value.

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  5. Nobody wants to deliver census forms to the Caves of Chaos.
    I wonder if the constant marauding of goblinoids could be a factor for the lack of density in fantasy worlds. Still only so much food/grain/meat to go around. Monsters are a plague of their own.

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    1. Good point, totally agree with that. My thinking was kind of like the settled nations of Greyhawk with large sections of plains that don't seem to have monsters around. Certainly these numbers could count as grand totals of all the humanoid races present.

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  6. I think I'd reduce the urban populations to about 40% of those numbers, bringing urbanization down to something more like 5% (my understanding is that Migration-era/"Dark Ages" Europe would be more like 1%!), making up the additional 300K population by calling them "waste dwellers": those tiny small village collections of families in the margins—call it one more order of magnitude down in population but no more in quantity, so about 35 population per each of about 10K small villages, mostly placed in the marginally habitable regions like swamps, deserts, savanna, badlands, steppe, high mountain valleys and dales, highlands, or the like. Otherwise, it all looks pretty good.

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  7. Just like you randomize village population, you could also randomize town population - say, roll 1d3*1000 for population. Then you get an assortment of small, medium, and large towns. Some supplies and equipment might only be available in the larger and busier towns. For example, if you want chainmail for a new hireling, perhaps that's no problem in a large town, but a smaller town might only have leather armor for sale.

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  8. City population looks a bit high - should be a lot lower, but more towns. Medieval urban populations rarely exceeded 5%.

    In the manorial system in NW Europe, AFAIK the baseline thorpe/hamlet was more like 100-120 people, enough to support one knight & his lance. I think 350-400 works well for walled hamlets in borderlands where they need to be able to defend themselves, so it is a common size IMCs. Few game settings resemble actual England ca 1200.

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    1. Thanks for checking that. You're right of course that I rounded the city value up so the total came out to a round number.

      That said, my source of Gies (Life in a Medieval City, p. 21) says circa 1250, Venice had a population of 100,000; Genoa and Milan, 50K to 100K.

      Then their other book (Life in a Medieval Village, p. 42) quotes Hilton as saying around the same time, 45% of villages had population below 400, 45% in range 400-600, 10% larger.

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