...If Japan here has parts of North America and Siberia, as well as Korea, along with Japan itself, wouldn't the population be a lot higher than that? Heck, the population of the Home Islands alone should be higher than that. Lordganon (talk) 06:12, March 5, 2014 (UTC)
Well, that depends. The Kalmar Union is 100 years behind us in technology - thus farming methods are probably worse - leading to less food and lower populations. :L 
Imp (Say Hi?!) 07:55, March 5, 2014 (UTC)
I'm surprised its taken this long for anyone to question the populations I've shoved in all over the place!
1) No one has invented the Haber Process yet. This means there is no widely available fertilizer.
(From Wikipedia: In combination with pesticides, these fertilizers have quadrupled the productivity of agricultural land: With average crop yields remaining at the 1900 level the crop harvest in the year 2000 would have required nearly four times more land and the cultivated area would have claimed nearly half of all ice-free continents, rather than under 15% of the total land area that is required today. Due to its dramatic impact on the human ability to grow food, the Haber process served as the "detonator of the population explosion", enabling the global population to increase from 1.6 billion in 1900 to today's 7 billion)
So crop yields aren't great and there'll be quite a bit of malnutrition.
2) Medicine is still at 1910ish levels so life expectancy isn't great and infant mortality is pretty bad.
3) The bits of Asia and America that Japan has here are hardly the most populated lands in the world OTL!
In general I've tended to take the OTL populations and then knocked off 30-40% and I've been quite brutal in some places. Yan Hoek (talk) 10:37, March 5, 2014 (UTC)
The home islands around 1910 had a population of ~45 mil. Korea probably had like 10-20 mil people, while Siberia is very lightly populated. The Americas is an interesting question, but if it has around 20-30 mil people, then we should end up with around 85-90 mil population overall (I think). Imp (Say Hi?!) 12:59, March 5, 2014 (UTC)
I have a large and colourful spreadsheet working out the population of all the American nations. By my figures (and there are a few minor ones I haven't filled in yet) the entire continent of Leifia has a population of 276 million of which half is in Mexica (Mexico, Texas + everything down to Panama). I don't think that's too crazy considering I've pretty much filtered out every major US and Canadian city. I have Japan's Leifian population at about 433,600.
So I guess that means that there's maybe 50 mil in the Home Is. 15 mil in Korea. 15 mil in Manchuria/Liaoning. The rest scattered about...
Maybe a map would be good to actually show what Japan has. I'll work on it next.Yan Hoek (talk) 13:14, March 5, 2014 (UTC)
This one, Yan, is really the first one that an obvious alarm bell rang about the population for.
The Haber process, imo, is not as significant as you think. And there's other methods for fertilizers that would have come into use instead, though admittedly not as efficient. Both you and wikipedia are exaggerating its importance.
Far more significant for the population increase of the last hundred years have been things like improved medicine and nutrition. In addition to the hundred years, obviously.
Your world may have its medicine behind otl, but it would be more spread out. The more time it takes to invent new ways, the more widespread the old ones will be. And, for that matter, the medicine would not be even with the otl 1910s, either. Vaccines, for example, are probably well ahead of the otl 1910s. Nothing like a massive death toll from disease to help in that regard.
And, for that matter, improved farming methods, irregardless of fertilizer, and new crops would still be out there, spreading. Another hundred years to increase because of that.
I would also bet on the numbers in Manchuria and otl eastern Siberia being higher than you think - less famines, and killing of natives.
No large numbers of immigration from Japan either, for that matter.
Overall population of this Japanese empire should be somewhere along the same levels as otl Japan has. So, in other words, like forty million higher.
Lordganon (talk) 08:10, March 24, 2014 (UTC)
Hmm, I appreciate what you're saying here but there's no denying that a huge number of the people here on earth OTL right now are a product of the sudden boom following WWII. I agree that a more widespread if 'backward' medical knowhow would certainly improve infancy and elderly survival rates while better sanitation would improve general health. I also agree that crops yields would also increase, however I fear without much definitive improvements in pesticides and fertilisers then much of this growth would be on marginal land more susceptible to the negative effects of weather, mono-culture and soil erosion. Without getting into Malthusian territory I do think we'd still be seeing famine conditions in certain areas in Africa and parts of Asia while the more 'robust' west would be close to the limits of food production. I'm wondering what the flooding and winter storms in England this year (on top of several years of generally crappy harvests) would have done to Wessex without automatic access to Canadian wheat for instance.
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Also its not like they just got to 1910 levels of tech a hundred years ago and then just stopped - which is my general bugbear with 'steampunk' - they have labored under antiquated systems for much longer than that. So their 1900 was equiv. to our 1825 for instance.
I guess what I've tried to do on a simple level is to keep the population growing at the same OTL rate without the massive exponential leap on the mid 20th century. So I've lopped off the 'extra' that improvements and technology has given us. So we're talking 3-4 billion people rather than 7.
Yan Hoek (talk) 12:25, March 24, 2014 (UTC)
The effects of that boom, however, are exaggerated - in basically every "western" country that saw a "boom" after that war, it was simply a return to the rough growth rates seen prior to the Depression.
Elsewhere, it was the impact of the better sanitation, medical care, nutrition, and crops that did it - resulting in the vast majority of the massive increases.
Really, a massive drop in infant mortality would alone cause such increases. Heck, it's been theorized, with good evidence, that even centuries ago, if you had taken out the infant statistics, the life expectancy would have been not all that far off our own.
Industrial fertilizers and pesticides were already in use by the 1910s otl - your world would have had them for a few decades by now, except Haber, since you indicate that.
Marginal land would actually be doing better here - so-called "cash crops" would be less of a factor, allowing better farming methods to be in use.
The areas you refer to as having famine conditions are like that otl, too. Tech means little for that one.
Wessex would have gotten the wheat still, just with slightly more difficulty. They'd have Norman wheat to fall back on too. Population of that one, mind, is right about what it should be.
The thing with that population rate, though, is that the massive "bump" is exaggerated. In developed countries, the same growth rate, barring the Depression, stayed in place for several decades before a cultural shift caused it to drop off.
Without the massive influx of modern techniques ala~ otl into the areas that are responsible for the massive increase, it would be a more moderate, level, increase - like in the developed countries otl - around the world.
Quite frankly, on average, you'd see populations about two decades ahead of the technological level you've established, give or take.