Something that bothers me...

[Kahoolin]

The better writers generally seem consider this and acknowledge the existence of female guardsmen/guardswomen. Although on this note it is very odd that all depictions of Cadian forces to date tend to be all male, even though it is VERY clearly stated that they induct both sexes without discrimination, this can be nothing more than simple shortsightedness on the part of the writers.

Yeah that bugs me too - the only guard regiment where in the actual codex it explicitly states that the birth rate is synonymous with the recruitment rate, and I can't think of any examples in fluff or fiction of female Cadians. It almost seems like they don't want there to be female Cadian soldiers but they just love saying "the birth rate and recruitment rate are synonymous" because it sounds tough.

[Melissia]

I've seen fluff describe hiveworlds as donating a percentage of their population every year to the Guard-- and these planets have hundreds of billions of people living in them-- and in fact that's just about ALL they tithe aside from some small trade goods produced in their factories. I'd say that there's a TON more Guard than GW's often rather mediocre writers let on.

[eldargal]

Ok, if you take Ichar IV, population of 500,000,000, and take a modern birth rate (say that of Grear Britain, lower than some developed nations, bear with me) of 10.65 births per thousand. 50,000,000 thousands, giving number of births per year of 5,325,000,000,000. So taking the modern (low) birth rate of Great Britain, Ichar IV could tithe five billion soldiers each and every year. This presumes that the tithe rate is geared to allow populations to remain stable. Now, if one assumes that the Imperium doesn't go in for contraception, needing as much meat for the grinder as possible, and encourages large families if we run the same numbers with the highest earth birth rate of 49.60 (Congo) we get a figure of 24,800,000,000 births per year.
If the imperium employs some kind of forced breeding program on some planets using the optimum arrangement of one man to every 6 females, then the birth rate could be truly astronomical. At some point excess females could also be inducted into the armed forces without compromising birth rate, which is what I think would happen on Cadia.
It is 4am and I've been painting and reading, so feel free to point out ant flaws in my math.

Edit: Thanks Melissia for pointing out I was leaving out some zeros. Fixed, read the calculator wrong.

I've seen fluff describe hiveworlds as donating a percentage of their population every year to the Guard-- and these planets have hundreds of billions of people living in them-- and in fact that's just about ALL they tithe aside from some small trade goods produced in their factories. I'd say that there's a TON more Guard than GW's often rather mediocre writers let on.

[Melissia]

Assuming you mean 500 billion for Ichar IV (that is, 500,000,000,000)? Keep in mind osme hiveworlds are described as having trillions. But anyway...

That would be 5,325,000,000 born per year with the UK's birthrate, and 24,800,000,000 per year using Congo's birthrate.

That is to say, between five and twenty five billion people are born every year on Ichar IV. Even if they only tithed enough to keep the population relatively even and prevent overpopulation, that would be a very high amount of Guardsmen. And even assuming a high death rate (which is believable given the nature of hiveworlds), that still means many billions of people are recruited every year.

Every YEAR. Over the course of a century this would be an unbelievable number.

[eldargal]

Well, take a hypothetical hive world with a population of two trillion and it could tithe 100,000,000,000 per annum. I think. As I said, this assumes a relatively natural (ie not forced, but no/little contraception) birth rate.
It also ignores infant mortality rates, which we have no information on. I would assume that the Imperium tries to maintain at least basic health and sanitation services, if only to not give Nurgle a helping hand. Even just clean water and basic sanitation on a subsistence level diet would keep the population relatively healthy.
Edit: The highest infant morality rate on Earth is around 180/1000 live births. If one ups it up to 250, arbitrarily, to take into account other hazards before one reaches conscription age, then that reduces the above figures by 25%. So taking the high figures for birth rate and mortality (they usually go like this in the real world, high mortality = high birth) then Ichar IV could still tithe 18,600,000,000 per annum.

Assuming you mean 500 billion for Ichar IV (that is, 500,000,000,000)? Keep in mind osme hiveworlds are described as having trillions. But anyway...

That would be 5,325,000,000 born per year with the UK's birthrate, and 24,800,000,000 per year using Congo's birthrate.

That is to say, between five and twenty five billion people are born every year on Ichar IV. Even if they only tithed enough to keep the population relatively even and prevent overpopulation, that would be a very high amount of Guardsmen. And even assuming a high death rate (which is believable given the nature of hiveworlds), that still means many billions of people are recruited every year.

Every YEAR. Over the course of a century this would be an unbelievable number.

[Melissia]

The highest population growth rate on earth ATM is 4.5% per annum. So on a planet with 1 trillion people on it, that would add up to around 4.5 billion babies born than die every year.

[eldargal]

Hm, less than I thought. How did I get 24bn from half a trillion then, lol. I shouldn't do math in the morning.

The highest population growth rate on earth ATM is 4.5% per annum. So on a planet with 1 trillion people on it, that would add up to around 4.5 billion babies born than die every year.

[Kahoolin]

If you ladies's maths are correct, and there are millions of worlds in the Imperium (many of which we can assume are hives, as unless a planet has a specific purpose it will eventually turn into a hive), then the guard is *ahem* freakin enormous.

Looks like the nids aren't the only race who can fight a war of attrition with limitless meat shields. And it really puts into perspective how weeny the Tau are. If there weren't bigger fish to fry (heh heh, fish eadz) the Imperium would have just rolled over them ages ago.

[eldargal]

In terms of planetary populations I really thnk someone needs to pay more attention to written fluff. Cadia is given a population of 250 million, which in todays terms ranks between Indonesia and the United States. This for the most heavily fortified and IG recruitment heavy worlds in the Imperium. 250 million soldiers would make sense.
But yes, even if the first lot of figures I worked out are completely rubbish, I suspect the Imperium could easily* maintain the Imperial guard at around one trillion men, taking into account death and attrition. Add to this PDF and mass conscription during serious crises.


*Not including supply and logistics.

[Melissia]

Hm, less than I thought. How did I get 24bn from half a trillion then, lol. I shouldn't do math in the morning.

You were doing birthrates, not population growth rate. Birthrate = just the amount of people being born. Population growth rate = the amount of people being born compared to the amount of people dying.