Population

[Juvenal]

I have just finished my first EB0.8 campaign (Casse). I very much enjoyed the experience - it was the biggest step-change for me in RTW since my first mod (RTR4).

I notice that population levels seem to max out within 40-50 years (I was obliged to exterminate most of my later settlement captures).

I wouldn't pretend to know what population rise is historically correct, but the current rate feels rather high. The effect on gameplay (for me) is that by the time I have money for more than one army, I no longer need to worry about casualties because of the inexhaustable supply of men from my settlements.

Please don't take the above as a criticism, but I would really like to know what is the current thinking on population.

PS. If this has already been discussed, could someone please give me a link.

[Gazius]

The current thinking is that it maxes out way too fast in the community, and I've heard talk of this being fixed in a later version, not .81. This is one reason I'd suggest playing with huge units, even if you have to lower the quality of anything else.

[PseRamesses]

Well, I´ve been whining about growth rates since RTW came out. It´s unrealistic that a settlement can outgrow itself imploding in squalor and unrest and almost a full rooster of troops is needed for garrisoning.

A series of speciall buildings could be constructed to hamper immigrants, right?! Or why not "buildable" decrees? Takes one year to build (implement) and reduces growth by x% with higher growth reduction the larger the settlement gets etc. Buildable decrees, laws etc would be a huge improvement to the game IMHO. what do you all think?

[blacksnail]

This is addressed somewhat in 0.81, but we will need feedback with population examples of longer-term play to help us determine the appropriate balance between population and squalor on a faction-by-faction basis. This is something that takes a lot of in-depth playtesting to balance right, and as this is an open beta a lot of the playtesting comes from the community.

[Juvenal]

I wasn't satisfied with just a vague feeling that growth was too high, so I have tried to model an upper limit on population growth. I am not familiar with demography maths, so I am doing this empirically.

Assumptions
Settlement population is number of males aged 15-50 (men of fighting age)
Couples are of same age (for simplicity).
Couples have children between ages 15-40 (i.e. for 25 years).

Mortality Rates (males)
Infant (0-14) 50%
Adult (15-44) 0%
Mature (45-64) 0%
Elderly (65+) 100%

Birth Rate
Assume 30% of adult females (15-40) stop producing children before age 40, due to death in childbirth, disease, malnutrition, accidents and loss of fertility.
1 couple, married at age 15 would have 16 children (out of a potential 25) in 25 years. This gives 4 boys and 4 girls surviving to age 16.
4 boys per couple in 25 years means 0.16 male children coming of age per year per men between 15 and 45.

Settlement Demographic
Assume men are evenly distributed between 15 and 50 years of age.
Proportion of new parents per year is 25 out of 35 = 71%
Coming-of-age rate per year is therefore 16% of 71% = 11.4%
Death rate is number of men becoming 65 = 1/35 = 2.9%

Conclusions
Result is 8.5% growth per year. That is no more than 2.2% per turn.

Even if infant mortality is zero, we only get 5% growth per turn.

Growth should be additionally limited by adult male mortality (disease, accidents, crime) and adult male sickness (making them unfit to fight). These could be offset by health and law buildings.

In my recent Casse campaign I was sometimes getting 8% per turn from recently exterminated settlements, so I think growth rates need to be cut back drastically.

Any comments or criticisms on my method would be welcome.

[JeffSteel]

In the case of exterminated cities having high growth rates for a while, wouldn't people start migrating to a recently "cleared out" city in hopes of obtaining cheap land or something? Kinda like a "land rush" of sorts.

[blacksnail]

In my recent Casse campaign I was sometimes getting 8% per turn from recently exterminated settlements, so I think growth rates need to be cut back drastically.

Extermination/enslavement is a bad example. There is always a boost to the growth rate of a city affected in that manner.

Any comments or criticisms on my method would be welcome.

We're trying for slower, more historically plausible growth rates in most cases. For example, Rome had a steady, roughly 1% growth rate per year during our time period. We're going to try to match that as well as we can, but it's a very careful balance between population growth and squalor.

[McHrozni]

I wasn't satisfied with just a vague feeling that growth was too high, so I have tried to model an upper limit on population growth. I am not familiar with demography maths, so I am doing this empirically.

Assumptions
Settlement population is number of males aged 15-50 (men of fighting age)
Couples are of same age (for simplicity).
Couples have children between ages 15-40 (i.e. for 25 years).

Mortality Rates (males)
Infant (0-14) 50%
Adult (15-44) 0%
Mature (45-64) 0%
Elderly (65+) 100%

Birth Rate
Assume 30% of adult females (15-40) stop producing children before age 40, due to death in childbirth, disease, malnutrition, accidents and loss of fertility.
1 couple, married at age 15 would have 16 children (out of a potential 25) in 25 years. This gives 4 boys and 4 girls surviving to age 16.
4 boys per couple in 25 years means 0.16 male children coming of age per year per men between 15 and 45.

Settlement Demographic
Assume men are evenly distributed between 15 and 50 years of age.
Proportion of new parents per year is 25 out of 35 = 71%
Coming-of-age rate per year is therefore 16% of 71% = 11.4%
Death rate is number of men becoming 65 = 1/35 = 2.9%

Conclusions
Result is 8.5% growth per year. That is no more than 2.2% per turn.

Even if infant mortality is zero, we only get 5% growth per turn.

Growth should be additionally limited by adult male mortality (disease, accidents, crime) and adult male sickness (making them unfit to fight). These could be offset by health and law buildings.

In my recent Casse campaign I was sometimes getting 8% per turn from recently exterminated settlements, so I think growth rates need to be cut back drastically.

Any comments or criticisms on my method would be welcome.

Yeah, you forgot migrations. Settlements are only city population, the majority of folks lived in the countryside. At the height of the Roman Empire, perhaps 30% of population were city dwellers (admittedly this wasn't surpassed until the 1870s or so), but for the most of the history and most of the regions, the number was probably closer to 5-10%.

So what happens after you exterminate a settlement? People from the sorrounding areas move closer to the city - cities were usually near rich farmland (that's what determined most city sites to begin with) - and soon came to live in the city.
You would also probably encourage some migrations by yourself through colonists, to improve the control of the area. Romans were particularily fond of that, but hardly unique.

McHrozni