[3.5] Demographics

[SillySymphonies]

Perusing the DMG's demographics system, I wondered what the expected number of total characters of each class in a community would be. In a thorp for example, one would expect 1/20 (96-100) x 1/6 (1d6) = 1/120 13th-level druid (i.e. 1 in 120 thorps houses a 13th-level druid). According to the DMG, the thorp has twice that number of druids of half that level (fractions are rounded down, according to the PHB). Continuing for all classes and levels, this generates the following thorp of 20 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids.
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


13th





1/256
1/120











12th





1/64
1/120











11th





5/128
1/120











10th





5/64
1/120




1/60






9th





31/256
1/120
1/64



1/60






8th





5/32
1/120
3/64



1/60






7th





11/64

3/32










6th





25/128
1/30
5/32










5th





91/256
1/30
3/16
1/8


1/30
1/8

1/16



4th





81/128
1/30
5/16
1/8


1/15
1/8

1/8



3rd
1/6


1/6
1/6
99/128
7/30
21/32
1/8



1/8

3/16



2nd
1/6


1/6
1/6
1 127/128
3/10
1 3/32
5/8


1/5
5/8

5/8



1st
1/627
1/627
1/4
5/6
5/6
290/999
1 7/30
2/209
1 5/8
1/4

2/5
1 5/8
1/4
13/815
1/4




Rounded to the nearest integers:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


4th





1












3rd





1

1










2nd





2

1
1



1

1



1st



1
1

1

2



2







I figured maybe others would find these interesting and/or useful? (Larger communities in the posts below.)

[SillySymphonies]

Larger communities (note that in a nonepic community the maximum level for any class is 20th):

A hamlet of 81 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


4th





1












3rd





1

1










2nd
1


1
1
2
1
1
1



1

1



1st


1
2
2
45
2
1
2
1

1
2
1
2
1




A village of 401 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


5th





1












4th





1

1










3rd





1

1
1



1

1



2nd
1


1
1
3
1
2
1



1

1



1st
2
2
1
2
2
326
2
11
3
1
1
1
3
1
18
1




A small town of 901 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


5th





1












4th





1

1










3rd
1


1
1
1
1
1
1



1

1



2nd
1
1
1
1
1
2
1
2
1
1


1
1
1
1


1st
4
4
2
3
3
763
3
25
4
2
2
2
4
2
42
2




A large town of 2,001 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


7th





1












6th





1

1










5th







1
1



1





4th
1


1
1
1
1
1
1



1

1



3rd
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1


2nd
2
1
1
2
2
2
2
3
3
1
1
1
3
1
3
1


1st
9
9
4
5
5
1,711
5
56
6
4
4
4
6
4
94
4




A small city of 5,001 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


11th














1



10th

1
1






1



1

1


9th

1
1


1



1
1
1

1

1


8th

1
1


1

1

1
1
1

1

1


7th

1
1


1

1
1
1
1
1
1
1

1


6th
1


1
1

1
1
1



1

1



5th
1
1
1
1
1
1
1
1
1
1


1
1
2
1


4th
1
2
2
1
1
4
1
1
1
2
3
3
1
2
1
2


3rd
2
1
1
2
2
3
2
6
4
1
1
1
4
1
3
1


2nd
5
6
6
5
5
10
5
4
4
6
5
5
4
6
5
6


1st
23
23
14
15
15
4,214
15
139
15
14
13
13
15
14
232
14




A large city of 12,001 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


20th





1












19th





1












18th


















17th







1










16th







1










15th
1


1
1

1







1



14th
1


1
1

1







1



13th
1
1
1
1
1

1


1



1
1
1


12th
1
1
1
1
1

1


1
1
1

1

1


11th
1
1
1
1
1

1


1
1
1

1

1


10th
1
1
1
1
1
2
1


1
1
1

1

1


9th





2

2










8th





1

2
2



2

1



7th
2


2
2

2
2
2



2

3



6th
2
3
3
2
2

2

2
3
2
2
2
3
2
3


5th
2
3
3
2
2
5
2
1
2
3
4
4
2
3

3


4th





6

8
3



3

2



3rd
8
6
6
8
8
1
8
4
6
6
4
4
6
6
9
6


2nd
4
6
6
4
4
23
4
17
9
6
8
8
9
6
5
6


1st
57
57
24
24
24
10,313
24
340
30
24
24
24
30
24
567
24




A metropolis of 25,001 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


20th





3

2
1



1





19th







1
1



1

1



18th
1


1
1

1
1
1



1

1



17th
1


1
1

1

1



1

1



16th
1
1
1
1
1

1

1
1


1
1
1
1


15th
1
1
1
1
1

1

1
1
1
1
1
1
1
1


14th
1
1
1
1
1

1

1
1
1
1
1
1

1


13th
1
1
1
1
1

1

1
1
1
1
1
1

1


12th


















11th


















10th





7

4
1



1

1



9th
1


1
1
1
1
3
2



2

3



8th
3
2
2
3
3

3
1
2
2


2
2
4
2


7th
3
4
4
3
3

3

2
4
5
5
2
4
2
4


6th
1
2
2
1
1

1

1
2
3
3
1
2

2


5th





14

8
2



2

1



4th
8
4
4
8
8
2
8
8
8
4


8
4
12
4


3rd
8
12
12
8
8

8

6
12
16
16
6
12
3
12


2nd
16
8
8
16
16
32
16
32
20
8


20
8
26
8


1st
119
119
40
48
48
21,701
48
715
52
40
32
32
52
40
1,192
40

[SillySymphonies]

Epic communities (note that the epic thorp, epic hamlet, epic village, and epic small town are identical to their nonepic counterparts described above):

A planar metropolis of 100,000 people:



lvl
adepts
aristocrats
barbarians
bards
clerics
commoners
druids
experts
fighters
monks
paladins
rangers
rogues
sorcerers
warriors
wizards


32nd





1












31st





1












30th





1

1










29th





1

1










28th





1

1
1



1





27th







1
1



1

1



26th
1


1
1

1
1
1



1

1



25th
1


1
1

1
1
1



1

2



24th
1
2
2
1
1

1

1
2


1
2
1
2


23rd
1
2
2
1
1

1

1
2
2
2
1
2
1
2


22nd
1
2
2
1
1

1

1
2
2
2
1
2

2


21st
1
2
2
1
1

1

1
2
2
2
1
2

2


20th


















19th


















18th


















17th





1












16th





2












15th





4

2










14th





3

4
2



2

1



13th
2


2
2
1
2
4
3



3

4



12th
4
3
3
4
4

4
2
3
3


3
3
5
3


11th
4
6
6
4
4

4

3
6
8
8
3
6
2
6


10th
2
3
3
2
2

2

2
3
4
4
2
3

3


9th


















8th





6












7th





15

12
3



3

2



6th
12
6
6
12
12
3
12
12
12
6


12
6
18
6


5th
12
18
18
12
12

12

9
18
24
24
9
18
5
18


4th





12

1










3rd
24
12
12
24
24
36
24
47
30
12


30
12
39
12


2nd
24
36
36
24
24
25
24
2
18
36
48
48
18
36
9
36


1st
487
487
96
96
96
88,705
96
2,924
96
96
96
96
96
96
4,874
96

[Biggus]

I figured maybe others would find these interesting and/or useful? (I'll post larger communities in a bit.)

Interesting yes, useful sadly no, at least for me personally. The DMG demographics are idiotic, as demonstrated by the figures for the thorp, which out of 20 people has 2 first-level Fighters and 2 first-level Rogues but no first-level commoners, despite the fact that they make up nearly 90% of the overall population. And that's before we get into the absurdity of things like 20th-level commoners existing...

[rel]

In my experience the demographic tables can be useful for creating a settlement but are much more useful for on the spot detailing.
The PC's enter the town of Dirt, up till now a name on a map and ask me if they have a cleric. I roll on the tables and come back with the answer no but they do have a high level druid.
Finding the druid and getting them to cooperate could be interesting. And the presence of said high level tree hugger will help with my descriptions.
The tables give me more to work with than a 50% yes no roll

[lylsyly]

So a thorp of twenty people has a level 13 and the small city of 5000
only has an 11th?? Do I really have to state where I'm going here?

[InvisibleBison]

So a thorp of twenty people has a level 13 and the small city of 5000
only has an 11th?? Do I really have to state where I'm going here?

I think it's perfectly reasonable for high-level druids to be more common in rural areas than urban ones. Also, thorps aren't guaranteed to have high level druids; there's only a 5% chance of one being present.

[D+1]

"When the PC's come into a town and you need to generate facts about that town quickly, you can use the following material." - 3.0 DMG

NONE of the community demographics information was intended to build an entire game world with, much less without direct sensible input from the DM that would always supersede it. It was designed to provide information on the fly so that a DM pressed for time or having been caught unprepared by circumstances had SOMETHING to work with right away. Then, IF more information was still necessary they could LATER create the data for the community in detail themselves as they saw fit according to what they actually needed or wanted in their campaign.

When 3.0 players read this section, however, they failed to read that quote above - the first line of the whole section. They then proceeded to universally and unwaveringly assume that all game worlds were meant to be made using only this system, and that all home game worlds were similarly expected to conform to it without fail: "What do you mean there isn't an 18th level wizard here? We specifically came here because it's big enough that the demographics STATE that there WILL BE one! I demand that our PC's be permitted to find the 18th level wizard as is our RIGHT!" People STILL want to parade it as an example of broken rules when it's only supposed to be a temporary tool to be used superficially.

Similarly...
"Prestige classes allow DM's to create campaign-specific exclusive roles and positions as classes." and, "Allowing PC's access to prestige classes is purely optional and always under the purview of the DM. Even though a few examples can be found below, prestige classes are idiosyncratic to each campaign, and DM's may choose to not allow them or to use them only for NPC's."
...Not at all the way they were ever actually treated.
:smallsigh:

[Fizban]

"When the PC's come into a town and you need to generate facts about that town quickly, you can use the following material." - 3.0 DMG

NONE of the community demographics information was intended to build an entire game world with, much less without direct sensible input from the DM that would always supersede it. It was designed to provide information on the fly so that a DM pressed for time or having been caught unprepared by circumstances had SOMETHING to work with right away. Then, IF more information was still necessary they could LATER create the data for the community in detail themselves as they saw fit according to what they actually needed or wanted in their campaign.

When 3.0 players read this section, however, they failed to read that quote above - the first line of the whole section. They then proceeded to universally and unwaveringly assume that all game worlds were meant to be made using only this system, and that all home game worlds were similarly expected to conform to it without fail: "What do you mean there isn't an 18th level wizard here? We specifically came here because it's big enough that the demographics STATE that there WILL BE one! I demand that our PC's be permitted to find the 18th level wizard as is our RIGHT!" People STILL want to parade it as an example of broken rules when it's only supposed to be a temporary tool to be used superficially.
I think the actual average is quite the opposite: most people don't seem to be aware of the city demographics at all, or if they are, say they're terrible (in both directions, either expecting far more high level NPCs, or that the small number should have already broken reality). Meanwhile every city with published information conforms to that section at their core, sometimes with added NPCs or stated reductions but still clearly marking the highest level characters for each class etc.

Also, there is no city size that guarantees an 18th level wizard (unless you use the ELH tables, which are shockingly enough meant for games that to go Epic Level). The maximum range for Wizard is 13th-16th, in the largest possible city (Clerics have 13th-18th, still with no guarantee of the top levels, and don't forget to roll alignment. . . ). Which is precisely why paying attention to the city generation is important for world building: even if you only use them for cities you haven't fleshed out, suddenly having a higher (or not high enough) level NPC where you don't expect it is a problem. If you only place NPCs at your personal whim, then you need to build everything. If you have a random generation table, you need to know its limits so you can use it correctly, by placing towns of the appropriate size to generate NPCs of the correct level to support the PCs.

The usual problem is the exact opposite: DMs that don't care about logical placement of leveled NPCs at all, and just throw whatever they want wherever. Entire dungeons or armies full of 8th level fighters, 10th level "cultists," etc (usually because they would rather build and play their classed NPCs than, ya know, use monsters from the monster manual). None of which makes any sense when the party had to level up from 1st and the NPCs have less gear and outnumber the PCs X to 1 meaning they apparently cut through X times as many challenges as the PCs did in order to supply this one dungeon with high level NPCs for them to cut through.

There's also the secondary problem that I'm pretty sure most DMs use far more big cities than they should. There should be like one metropolis in all of Europe, but people look at Forgotten Realms and see it has a bunch of them, and even Eberron has 2-3 I think- or they just figure that every major political entity should have a metropolis, and so their worlds do indeed have a ridiculous number of high level characters, generated by cities that couldn't possibly exist on the land available. And if there's only one, well yeah, the party making a journey to literally the biggest city in the known world in search of the most powerful Wizard to petition them for aid, and still having no guarantee that person can cast (or if they can, even knows the particular) 9th level spells they need. . . that's perfectly appropriate.

"Prestige classes allow DM's to create campaign-specific exclusive roles and positions as classes." and, "Allowing PC's access to prestige classes is purely optional and always under the purview of the DM. Even though a few examples can be found below, prestige classes are idiosyncratic to each campaign, and DM's may choose to not allow them or to use them only for NPC's."
...Not at all the way they were ever actually treated.
:smallsigh:
To be fair, the number of Prestige Classes actually used in a game, just like the feats and spells and base classes and everything else, is limited to those actually in use. Anything not already on a sheet or shown by the DM could at any time be ruled to not exist. If the DM isn't using things themselves but is tacitly allowing any X/Y/Z rather than stating what is available, it can be taken that they are essentially allowing the players to fill out the world with the organizations/etc that support the prestige classes they're actually taking or plan to take. That so many DMs would rather just let people use "any 1st party" material rather than define a world can be disappointing, but then, I wouldn't want to build a world and organizations and pick or build a bunch of prestige classes linked to them knowing that the players won't actually care and would rather pick their own from a book. One of the major factors against putting a bunch of effort into such a project is knowing that the players probably won't care or even notice unless you shove it in their faces, at which point you look like you're using them to play around with your special snowflake DM stuff instead of focusing on the group.

The only way you can make people care about your setting specific material is when: the game starts from a sufficiently limited set that your additional material is some of the only options, or your material is mechanically powerful enough to overshadow published material they're aware of, or your material is so perfectly suited to their character concept that you essentially must have made it for them rather than for the setting.

Considering how frowned upon the limiting of sources is by a community which is based mostly on char-op'ing published material, and the power level that community expects, you're left with the only stuff players care about being that which you specifically created for them rather than devised for your own setting. So you are quite correct in that perceived community mindset of content inclusion goes quite against what the DMG says (not just for PrCs, but all content of course). Even on the rare occasion I've heard that a DM made a cool setting-linked prestige class, it's usually in conjunction with limits on available published material.

[Elves]

Similarly...
"Allowing PC's access to prestige classes is purely optional
Agree w/ you on the demographics, but the attitude in this quote stopped at the point where every player-facing supplement was crammed with prestige classes. When 3.0 started PRCs were an experiment but they became normalized.

[Particle_Man]

This might be where “A Magical Medieval Society” could be of use.

https://www.drivethrurpg.com/m/product/192370

One of the chapters from the book, “A Magical Medieval Society: City Guide”, is free (or pay what you want):

https://www.drivethrurpg.com/m/product/55264

[SillySymphonies]

The DMG demographics are idiotic, as demonstrated by the figures for the thorp, which out of 20 people has 2 first-level Fighters and 2 first-level Rogues but no first-level commoners, despite the fact that they make up nearly 90% of the overall population.
Only for the smallest possible community of 20 people. A thorp of 80 people is expected to have 55 1st-level commoners (69%).



And that's before we get into the absurdity of things like 20th-level commoners existing...
According to the DMG, commoners farm the fields, staff the shops, build the homes, and produce the goods. So I'd guess the highest-level commoners to be the heads of their respective guilds?



NONE of the community demographics information was intended to build an entire game world with, much less without direct sensible input from the DM that would always supersede it.
Teleportation circle definitely wasn't intended to, and Emperor Tippy has done just that. 🤷



They then proceeded to universally and unwaveringly assume that all game worlds were meant to be made using only this system, and that all home game worlds were similarly expected to conform to it without fail: "What do you mean there isn't an 18th level wizard here? We specifically came here because it's big enough that the demographics STATE that there WILL BE one! I demand that our PC's be permitted to find the 18th level wizard as is our RIGHT!"
'In addition, not every town or village has a spellcaster of sufficient level to cast any spell. (...) Even a metropolis isn’t guaranteed to have a local spellcaster able to cast 9th-level spells. (https://www.d20srd.org/srd/equipment/goodsAndServices.htm#spell)'



Also, there is no city size that guarantees an 18th level wizard (unless you use the ELH tables, which are shockingly enough meant for games that to go Epic Level).
I began adding the epic communties (starting with the planar metropolis).



There's also the secondary problem that I'm pretty sure most DMs use far more big cities than they should. There should be like one metropolis in all of Europe, but people look at Forgotten Realms and see it has a bunch of them, and even Eberron has 2-3 I think- or they just figure that every major political entity should have a metropolis, and so their worlds do indeed have a ridiculous number of high level characters, generated by cities that couldn't possibly exist on the land available.
According to the DMG, 1 in 100 communities would be a metropolis (upwards of 6% of the overall population) and 1 in 25 a large city (up to 43% of the overall population)



To be fair, the number of Prestige Classes actually used in a game, just like the feats and spells and base classes and everything else, is limited to those actually in use. Anything not already on a sheet or shown by the DM could at any time be ruled to not exist. If the DM isn't using things themselves but is tacitly allowing any X/Y/Z rather than stating what is available, it can be taken that they are essentially allowing the players to fill out the world with the organizations/etc that support the prestige classes they're actually taking or plan to take. That so many DMs would rather just let people use "any 1st party" material rather than define a world can be disappointing, but then, I wouldn't want to build a world and organizations and pick or build a bunch of prestige classes linked to them knowing that the players won't actually care and would rather pick their own from a book. One of the major factors against putting a bunch of effort into such a project is knowing that the players probably won't care or even notice unless you shove it in their faces, at which point you look like you're using them to play around with your special snowflake DM stuff instead of focusing on the group.
❤



Agree w/ you on the demographics, but the attitude in this quote stopped at the point where every player-facing supplement was crammed with prestige classes.
Sadly, yes.

[Fizban]

Teleportation circle definitely wasn't intended to, and Emperor Tippy has done just that. 🤷
Heh. The irony of RAW is that you can always find RAW someone doesn't like.


According to the DMG, 1 in 100 communities would be a metropolis (upwards of 6% of the overall population) and 1 in 25 a large city (up to 43% of the overall population)
True, but that information is useless without knowing how many communities you should be making per area, which the DMG gives no information for unless I missed something major. And actual rolling introduces the effect where instead of 1/100, you could find one on the first roll or not for 200 rolls. A DM can "follow the rules" there by simply stating that there are an extra 100 other arbitrary communities for every one of their arbitrary metropoli.

The book A Magical Medieval Society has been suggested (which I've not picked up myself), but for this I've already found the free resource Medieval Demographics Made Easy (https://takeonrules.com/assets/downloads/medieval-demographics-made-easy.pdf) plenty sufficient to figure out how big of an area you need to support the towns you want, or to fill an area with appropriately sized towns, which you can then otherwise generate with the DMG's city rules.

[icefractal]

The demographic rules aren't perfect, but IMO they're better than nothing, and "basically nothing" is how much consideration is given to demographics in many campaigns and published adventures.

Personally, I think "Go to a specific other plane? That's pretty rare - to find someone who can do that, we'll probably need to visit a large city at least, and a metropolis would be more of a sure bet. (And if the PCs become able to do that, people might seek them out for assistance)" is more interesting than "It's however easy or hard fits the plot best."

[Palanan]

For a more detailed look at these issues, this critique of MDME (https://medium.com/migration-issues/notes-on-medieval-population-geography-fd062449364f) gives more precise estimates, and points out some essential facts of medieval life and history which MDME glosses over. Worth a read, and for fans of GoT, the author has also critiqued the demographics of Westeros.

Also, this recent paper (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5051806/pdf/pone.0162678.pdf) is worth a look as a broad-scale overview. It’s not a demographic survey per se, and they’re more interested in modeling social networks, but it’s still an interesting read, and the bibliography has some great sources to follow up on.

[Yahzi Coyote]

Those demographics are completely useless. A single 20th level caster redefines everything within a thousand miles, so you can't wander over a river and suddenly find one. The random encounter tables are worse: you can be walking through a large city and suddenly encounter half-a-dozen 14th level casters that you previously never knew existed.

I detail a much more reasonable system in Lords of Prime (https://www.drivethrurpg.com/product/217953/Lords-of-Prime), where the rank of the ruling class is based on the size of their domains. I also double the XP for every level, so my world tends to top out around 9th level NPCs, which I think is necessary to maintaining even a vaguely medieval world.

I automated all of those generation rules into a program: Sandbox World Generator (https://www.drivethrurpg.com/product/217951/Sandbox-World-Generator). You can push a button and generate an entire continent, and then troll through it looking for interesting things. The game recap I am running (World of Prime: Campaign Journal) is set in a world generated by that program.

[icefractal]

Those demographics are completely useless. A single 20th level caster redefines everything within a thousand miles, so you can't wander over a river and suddenly find one. I don't see any 20th level casters showing up in those demographics - the highest Sor/Wiz are 16th level, the highest Cleric/Druid are 18th. I'm not counting the Epic one, because ELH stuff massively changes the world if included.

That's still very powerful, but there's only a handful of those in a metropolis, and none in the smaller settlements. So unless your world is packed with cities like Ravnica, you're not running into really high-level casters very often.

Something that is dumb, both in terms of fitting the demographic rules and in terms of world-building, it's the "Spellcasting Services" table. 1800 gp for a 20th level archmage to cast a 9th level spell on your behalf? A price that's not even sufficient to buy a minimum-strength Headband of Intellect for one of her apprentices? Offered to someone who could easily be the ruler of a kingdom if she wanted to, and can (by default at least) go to the Plane of Earth for gems as required? Yeah, that's just silly.

[Telok]

Do note that of you're using this to populate the smaller villages there's that 1/10 (if I recall correctly) chance of a mid-high level druid or ranger. With the relatively large numbers of small population centers this leads to a truely surprising count of druids, to the point where they may outnumber the other caster classes combined.

[sreservoir]

Something that is dumb, both in terms of fitting the demographic rules and in terms of world-building, it's the "Spellcasting Services" table. 1800 gp for a 20th level archmage to cast a 9th level spell on your behalf? A price that's not even sufficient to buy a minimum-strength Headband of Intellect for one of her apprentices? Offered to someone who could easily be the ruler of a kingdom if she wanted to, and can (by default at least) go to the Plane of Earth for gems as required? Yeah, that's just silly.

Relatedly, the prices of scrolls and how this interacts with community gp limits imply that despite the general nonexistence of 17th-level wizards and sorcerers, scrolls of 9ths are "most likely available" in any small city, all exceptions temporary.

[bekeleven]

If the DM isn't using things themselves but is tacitly allowing any X/Y/Z rather than stating what is available, it can be taken that they are essentially allowing the players to fill out the world with the organizations/etc that support the prestige classes they're actually taking or plan to take. That so many DMs would rather just let people use "any 1st party" material rather than define a world can be disappointing, but then, I wouldn't want to build a world and organizations and pick or build a bunch of prestige classes linked to them knowing that the players won't actually care and would rather pick their own from a book. One of the major factors against putting a bunch of effort into such a project is knowing that the players probably won't care or even notice unless you shove it in their faces, at which point you look like you're using them to play around with your special snowflake DM stuff instead of focusing on the group.My worlds tend to have defined organizations, which have no bearing whatsoever on what classes PCs have access to.

I am all the way to the line on "classes are mechanics." Sure, some have alignemnt or conduct guides we can talk through on a case-by-case basis, but in games I run, fluff is fluff and mechnics are mechanics. One of my favorite chracters was a mage who was (on paper) a single-classed barbarian. He was still, in the universe of the game, a wizard. He spent a lot of spell slots on mage armor and expeditious retreat and tended to favor short-range attack spells, but his special techniques made them not provoke attacks of opportunity. He also took Cause Fear (ranks in intimidate).

So, I don't constrain classes by flavor, but I do constrain organizations.