I saw someone suggest that the world begin entirly populated (albit low density). I was inspired to try and merge my village system with this idea.

The overview: (this is what the player sees, it should not be too complicated from the front end, even if it is mathamatically involved from the rear).

This assumes the x10 resource system and a few of my favorite resource management ideas.
Population is represented by 'heads' of ~100,000 people, but population is stored as a real number. For desplay purposes it is rounded of at thousaths (form P=xx.xxx)
Three resource can be harvested from terrain squares.

Consumables (Con): represent food as well as other consumer goods (cloths, materials to build housing, etc.) This is a better representation than straight food, as the same land can often be used for growing food or for cash crops (cotton, tobbaco) but under this umbrella it all can be acounted for. Consumption per person depends on government type. Modern prosperous governments consume more, but people tend to output more.

Fuels (Fuel): represents fuels and non-permantnt stuructural organtics, such as wood. Fuel is a small part of the build cost of units, but a major part of teh maintenance. Even ancient units use some, in the form of replacing leather armour, wooden chariots, and spear shafts, etc. Modern units and impovments use much more, but oil and uranium resources suppy MUCH more than forest, once the technology allows.

Metals (Metal): represent structural metal used to build improvments and units. Ancient sources are from copper & tin, later iron deposits are added, and modern is alluminum. The more modern types of depsoites produce more per turn.
(note: it doesn't matter if your metal comes from a copper deposit or an alluminum/titanium deposit, they still count the same (it is a common pool for simplicity) but an alluminum deposit produces much more). Same applies ot Fuel.

Each square has a production value of each of teh three catergories, which can be improved by terrain improvments.
Each square also has a population. The actaul production of a square depends on the population and the raw resource value. The higher the population the less effective each person is in production. At a population of 1 head, actual production = raw production.

All production is pooled nationaly (or regionally if people prefer). There is a efficiency bonus for better government and transport infrastructure.

Cities produce Labour and currency/science/luxuries (call it Trade, which is then subdivided ito the previous catergories.

The square a city is on is also a village, with it's own population, since all but the largest modern cities don't cover that much of a square, but when you build a city, the rural population is used to found the city, and more people migrate in to repopulate the rural areas.

Labour is used to build Units, Improvments, Wonders and TI's. Depending on the final system, labour could be kept at each city, or pooled nationaly, with multiple builds per turn, and multiple queues for each type of build.
Bulding stuff also requires resources, mostly in the form of Metal and Fuel.
Resources can be stockpiled and sold, but labour is used imidiatly.
Rush buying works by paying Currency to multiply a citie's Labour output.

Population growth
The population groth of your civ depends on having excess Consumables and government, tech, and infrastructure. This is all used to get a %Growth value. This represents the %pop increase per turn.
A total of CivPop*%Growth heads are added each turn. Remeber this is all calculated using real numbers, so all fractions are carried.
The new population is then divided into rural and urban pop, based on your current pop distribution (you can encourage people to move from one to anouther, more later), with a adjustable slider as a modifier. The limits depend on government.

Rural population growth is placed propotional to the increase in production on a square. More on this later.

Tranportation, and player effects can modify this.

Urban pop growth is placed similiarly, based on per capita productivity, modified by happyness and player effects.

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The nitty gritty ( I woarn you this may get a bit complicated, but it covers areas that the player wouldn't see most of the time)

The Raw production of a square is the same as normal (x10 for CIVII). This repersents how much 1 head of pop. would produce.

The Real production = [ln(Pop +1)/ln(2)] * Raw.
This gives a logarithmically decaying productivty adjusted to have 0 at 0 pop and 1*Raw at 1 pop. At 3 pop = 2*Raw, and 7 pop = 3*Raw.

For information the percapita production = [ln(Pop + 1) / ((Pop + 1)*ln(2))]*Raw

Population is distributed based on the increased production a small increase in pop would bring. Remeber that the average productivity goes down with the increase so I used the differntial increase.
This factor is 1/[(pop +1) * ln(2)].
The player has slider a and b, wich set the pririty of Fuel and Metal vs. Consumables. This allows the player to encourage the growth to focus on production increases in each area. The sliders range from 0 to 2.

Each square has a growth factor. It is calculated as
fGrow = mod*(Cons + a*Fuel + b*Metal)/[(pop +1) * ln(2)]
where 'mod' is a constant that depends on player flags, transport TI's and enemy units.

Population can be on costal ocean squares. It is really on teh coast, but it is represented as a pop on the ocean square.

mod defaults at 1
*2 river
*1.5 ocean
*0.5 tundra / swamp
*2 for road (negate if RR also)
*3 for RR/Highway
*2 for player flaging a square for growth (costs some Currency)
*0.25 for player flagging for no growth.
*0.5 for border squares
*0.5 for enemy unit adjacent
*0 (no growth) for enemy unit on it.
*0.25 for radiation
*0.5 for pollution

The player can flag squares for extra growth and for preventing growth.

The fGrow values for all squares in your territory are summed = SumGrow

The population added to each sqaure is Sum of new rural pop (RuralNew) * (fGrow/SumGrow)
These are real numbers, so growth may not be noticable every turn on each square, but it happens.

Population dislocations.
Production of millitary units requare a small amount of pop (representing the pop tied up in service), of order 0.05 -0.1 heads for land combat units, and less for everything else. This is lost if the unit is destroyed. It is freed when it is disbanded or placed on 'reserve' status. Repairing units requres
rPop = 0.5 * %damage_repaired * BuildPop.

Dislocated citizens.
Dislocated citizens are added to the pool of RuralNew, and get placed just like new population in teh next turn.
The player can choose to pay citizens to dislocate (costs depend on Gov.), maximum 1/2 pop of the square.
Enemy units passing over a square causes a small amount of dislocation, comabt does much more, and causes some permanant loss, as does radiation.

At the start of the game the pop depends on the value of the square * mod(for river and ocean)
So a plains might get 0.02 pop, while a forest river special resource might get as high as 0.1, and a tundra 0.001.
All sqaures inside your border are used, borders can extend 1 sqaure into the ocean.

Questions/ comments?

Heads have different types. Theres the basic Man and Woman head which shows the total and how many of each. This is the start head screen. Then you can go into others.

age-Adults, Children, Elderly

jobs-corporations, business, unemployed, gov,
science, entertainment(maybe)

religion-

class-lower, middle, upper

etc

I don't like consumables, just goods or something and have food seperate.

2 types of each, in modern times 2nd generation stuff is needed

Food>processed food
goods>manufactured goods
construction materials>refined materials
fuels>engine fuels

each square should produce something but as better technologies come around squares are less and less used for mining and growing and more just as a place to live. Most countries have forever have had a fertile area that produced the most food as well as local food. Cities would need a certain amount of each to build units but not improvements should cost more money than construction materials.

these goods wouldn't be only for modern and industrial ages. The phalax should need refined goods(clean bronze). Legions need construction materials and refined materials to be built and repaired but not supported. A direct supply line from a region with food and possibly goods and fuel is needed or the unit will be hurt. Regions can be newly conquered ones too.

At first people will move from villages to cities then back during depressions or wars. As time goes and if your empire has a fall, or near fall or recession villages will pop up everywhere. Also there shouldn't be any villages in the middle of the desert. Jobs should be important so if the village is in a fertile soil area chances are its going to be mainly farming. Whole regions could be mainly farming with a capital city for exporting.

labor should be the form of jobs. Companies or guilds for construction would provide the labor for construction and keep people in jobs and not unemployed thus not ready to riot because they can't afford food. Wonders could need government job searches or something and a good way to lower unemployment. Rome had big problems with unemployment and had to give a lot of food away. Unemployment would be money and you could thread the line between losing money, spending the money on creating jobs(theoretically) or keeping the money for something else. Here's where wars that stimulate the economy come in. It makes the game more realistic.

Everyone has a job,
business, small business includes guilds for construction or companies. Service industry everything not in other categories

government, this is improvements that can't be sold to people or corporations and military as well as a certain amount for infastructure

corporations, unrealistic but good for gameplay hire many many people

unemployed, pretty obvious they suck up money and give nothing back but can riot if there is too many.

jobs+standard of living+religion and stuff should decide how people migrate.

The technical stuff is ok as you stated it, plus Firaxis can do some of that

I've expanded my suggestions into a mini model I'm sorry, no wait no I'm not