First, some general stuff and definitions.
There are five resources in Pandora: Food, Minerals, Science, Production and Credits.
The population of cities produce the resources above by being assigned a job: Farmer (food), Miner (minerals), Worker (production), Scientist (science). All population members, regardless of their job, produce credits based on based on the tax rate slider.
Since the tax slider is very easy to understand, I'll not discuss it much here, and instead focus on the distribution of workers between the other jobs.
The first two jobs put the worker on a tile on the map. Call them "gathering" jobs. The second two do not rely on territory on the map. Call them "indoor" jobs.
Only Production is accumulated locally, at the city where the work is done. All the other resources go into a faction-wide pool. That means that except for a few workers in each city (to get buildings made as the city grows), you can be very flexible in where you gather the other resources.
Population growth is not affected by any resources, as long as you're not starving (that is, you have a positive food stockpile). The number and size of your cities, and their individual morale level will affect the distribution of growth (via migration) but not the total amount, faction-wide.
Now, here's my thesis: Your economy is limited by the productivity of your workers doing their jobs. Gathering jobs require some thought to get high productivity at, so they should be the focus of your economic planning.
This is pretty simple to understand. Population doing indoor jobs are usually identical to one another, from a productivity standpoint, unless there are Xenite Flowers or an Observatory in the city's range. (If there are, you want to maximize population doing the job that gets that bonus.) For outdoor jobs, however, there are big differences depending on what territories is being farmed or mined.
I rarely assign gathering jobs in territories that yield less than three resources. Getting three resources per worker (before building bonuses) is a 50% better per capita output than getting only 2. That's huge. That's the size of the (perhaps unbalancedly big) faction bonuses. This is the biggest improvement that I think you can get from micromanagement of your economy.
So I put my mines in the mountains (or where there is a mineral bonus) and my farms on grassland or tropical plains (or where there's a food bonus).
I never work tiles that yield only one resource, and I don't imagine I ever will unless my economy is completely coming apart at the seams.
Tiles that yield 2 resources, like ocean, farmed tundra or savannah, and mined hills are marginal. I don't work those tiles unless my economy is out of balance due to some sort of shock (like a new tech unlocking a building I want to build everywhere ASAP, or a recent conquest bringing in dozens of new citizens who I have to feed even while they're rebelling). It's good to have access to the marginal tiles, but if my economy is firing on all cylinders, I'm not going to be working them.
When I'm constrained by resources (rather than my ability to defend against the natives or other factions), I avoid building cities in the middle of large areas of marginal terrain. A city in arctic mountains or featureless grassland plain is far more productive at gathering resources than one in a bunch of hills, or by the seaside in the tundra. Cities with both fertile plains and mountains are of course the best of all, but there's no need to worry about having both in one place, you just want a lot of either.
My work assignments then flow directly from the terrain I control. I gather from the highly-productive terrain, and put the rest of my workers into indoor jobs, with maybe a few workers gathering in marginal land if things are a little off balance.
Since this is a computer program (and the AI should be able to reproduce my strategy), here's roughly the algorithm I follow for assigning jobs to my population:
- Gather from all tiles that yield three or more resources.
- Most of the rest of the population should work inside jobs.
- If a city has a bonus to research or production (from Xenite Flowers or an Observatory), focus nearly all of the indoor-working population on that type of job.
- In the rest of your cities, make a balance of workers and scientists such that you use the rest of your gathered minerals. How you distribute the workers and scientists between these cities is largely arbitrary, but you may want a larger proportion of workers in new cities (to build buildings) and on the frontiers (to build military units).
- If there's a food shortfall (that's large relative to my stockpile and expected future needs) assign a more farmers on lower yielding tiles (like ocean). Not starving is of critical importance! If you're chronically short of food, look around for an area of fertile plains and build a farming city there.
- Alternatively, if there's a large food surplus, a few productive farms can be left fallow until they're needed as the population grows. If the surplus is persistent, found some cities in mineral-rich but food poor areas. Or if expansion is impractical (due to natives or other factions), you could instead plant forests on some plains tiles near your production-focused cities, rather than farming them.
- If a city has a lot of pollution, reduce its number of workers a bit in favor of scientists. Consider planting forests on that city's marginal tiles.
- If you have a short term need of a lot of production (such as rolling out a new building everywhere), you can move some scientists to be workers and others to be miners on marginal tiles (e.g. mined hills).
I don't think the AI uses this algorithm. I see it building a lot of cities in the middle of big areas of hills, and mining them. I also see the AI farming a lot of tundra/savannah, rather than putting forests there and farming in better terrain (with additional cities, if necessary). Of course, I can't actually tell if its working the tiles it prepares, so it could just be poor former AI (terraforming territories that won't be worked), rather than poor work distribution.
There are also a few other AI city placement or development issues, like the Green faction's formers building mines rather than forests on hills, when both yield two minerals.
I've also seen AI capitol cities placed where they can't possibly get enough food to sustain their growth at the start of the game. Do they get extra food on "hard" difficulty? The first city I saw do this grew to at least size 10 in tundra hills with at most 4 food from the terrain inside the center ring (if you add two for the HQ and two more for the first tier of farm building, plus 1 more from that building's 25% farmer bonus, you still get only 9 food, and that city will have terrible productivity, farming forests for 1.25 food each). The AI built no farms before its next city was founded in slightly better terrain. Building non-capitol cities in infertile terrain is OK as long as the faction-wide food balance remains positive (a small deficit is fine too, for a while).
