The guidebook for map 6 isn't quite up to scratch in some aspects. Firstly, it has no "civ" rating for the settlements. Secondly, and rather more dramatically, it has no entry for the City State of the World Emperor (CSWE) itself! No population, no overall alignment, or civ rating. Nothing.
After a brief discussion on Dragonsfoot, I went with an "able bodied" population of 30,000, giving a total population of 120,000, and a civilisation rating of 10 - the max. For other settlements I rolled or picked a civ rating. I set the CSWE alignment as LE.
As an example of picking, I put the military settlements such as Moon Tower and Midwall at 0 on the grounds that they are not in fact producing anything at all and since civ is defined in the CSIO guide as being primarily a rating of manufacturing ability that seemed reasonable.
One thing that jumped out at me was how much lower the population levels on Map 6 are. Aside from the huge CSWE, only Targnol Port breaks the 1,000 level. There's nothing to rival the City State in the way that Warwick or Ossary do for the Invincible Overlord.
A consequence of this is that although the CSWE does end up with more trade that CSIO, it is not as big a gap as the guidebook seems to imply - just over 20% more. Since the CSWE has an estimated 50% more people in it, this means that on average they are poorer than their eastern counterparts, at least in terms of traded GDP. The specific values for the combined maps are 26 to 33.
Here's the base map (light blue is withing 5 miles of land):
Are we there yet?
One big question was whether the main trade route from CSIO to CSWE would be by sea or land. Although the land route is shorter, the northern route past Warwick and into Quiff looked like it might work. As it turned out, it works for Warwick but it's too far for CSIO ships to compete with a mostly overland route.
That route runs west through Darkfield then across country, over the Battleplain Gwalion to cross the River Bucknol at the lower Quoth Crossing from whence another day and a half's march brings it to Caelam and the start of the Emperor's road network. Two days pounding pavement brings the route to the port of Augge where it embarks for the big city.
See sketch (click to enlarge):
The significance of this route to actual play, of course, is that it is the route that the annual tribute from the Overlord to the Emperor will follow - an event that is sure to be accompanied by much activity both in the wilderness and back in the city where many of the troops and higher level NPCs will be absent, assigned to protecting the caravan.
The trade from Warwick goes via Smitten, making it the 5th most important transshipment port on the combined maps (Augge is #1).
In terms of transshipment, Targnol is 15th and the city generally fails to live up to its billing as a major port, although it does come 4th in terms of trade volume. Augge is a much more important port. Adding the sparsely populated maps to the south won't change this, especially since those areas will sail directly to the port in CSWE itself.
Is This Making Sense?
As an almost final note on this subject, I would say that this examination of the trade routes and populations has confirmed what I had always felt about the setting: as demographics, it simply doesn't work. CSWE almost works in the sense that the are labelled "Emperor's Farmlands" is just big enough to support even a population of 120,000. Sadly, the city is not big enough, I think. Even with 5-story buildings of the sort the ancient Romans resorted to for packing the population of Rome into its footprint is probably not enough. The situation in CSIO is even worse. There's no way to fit 20,000 into CSIO, let alone the 80,000 total that the books suggest is the whole population including women, children, and the old.
Likewise, the lack of roads in the east means that getting food to CSIO from outlying settlements is pretty tough if the production is not hard by a river or the sea. With no equivalent to the Emperor's Farmlands, it's hard to see where the city's food is coming from. On the scale of the maps I've used, there is a need for 16,000 pixels of farmland (using JG's rules, which are not far off reality for the tech level). All the land west of the city between the hills, the Mermist, and the Troll Fens adds up to just under 6,000 pixels (60,000 acres). And that's not even open plain, it's "light woods". The city has no visible means of support.
The settlements of these two maps are very isolated from each other. There's very few towns that have more than one neighbouring settlement within a day's travel, at least for bulk trade purposes. As such, there's unlikely to be much shared culture and the "common tongue" will be very limited outside of trade subjects such as counting, quality, and dates. Discussions of ancient civilizations (and where to find them) is not going to be easy.
The length of trade routes means that caravans will be the norm, as overnight stops will be routine, and defensive measures absolutely vital. Likewise, the large towns will have to patrol wide areas to help keep much needed trade safe from gnolls, orcs, and dragons.
Ultimately, the Wilderlands is not about demographics, it's about adventure. This analysis is aimed at end-game factors for domain clearance. Where is the Overlord or Emperor likely to grant lands? What long-standing monster lairs would they want removed as part of such a deal? Where would the PC be able to offer colonists some economic future? And so forth.
The problems identified with the setting are really not too obtrusive and can even be handwaved away - the City States' listed high populations are perhaps just the total troops they can draw on across their whole domains; the cities themselves might be very much smaller. Perhaps magical food production allows the Overlord to feed his city.
Anyway, that's enough demographics for now. More religion next time.
Oh, one last thing. I did some maps to the south to test whether Ossary would take that route (it did not). I've only really done the coasts so far but in case anyone wants it, here's the larger map: