A province's Population is… well… its population. It isn't absolutely everyone in the province, merely the portion of peasant civilians. It is from the mass of people that Income, Supplies, and Recruitment Points are derived.

Every 100 people in a province provides a minimum of 1 lb. Gold of Income through taxation, rounded down. This is then added to or subtracted from by certain Magic Sites and random events, and modified by Fort Administration, Scales, and Unrest.

Only Population pays tax, of course, and units do not. Not even your righteous Prophet, who has no Upkeep, pays tax. In addition, the tax money of peoples in a fort-less exclave doesn't reach your Treasury, unless there's a Tax Collector within it.

• There are some exceptions to this, however. Sailing nations typically "trace income across oceans", for instance, so exclaves that can reach a fort through sailing still get their taxes to the treasury.

Recruitment Points roughly represent the availability of men for open positions in the army. These are from the small portion of men who don't really pay taxes, such as the vagabonds, lesser nobles, or warrior tribes, so recruiting a unit does not deduct from the Population.

In previous games, a province with zero people living in it had zero Recruitment Points. In this game, every province has a base of 20. This scruff group of survivors can always be drawn from, amounting to around two mundane soldiers per turn (if Resources allow), though a Population-less province will not provide the Gold for hiring them. Atop that twenty, added portions of Population provide extra Recruitment Points with somewhat-diminishing returns:

Fortunately, Forts (representing a city, or a colony of the faction, or both) provide a significant multiplier for Recruitment Points. For instance, mere Palisades increase Recruitment Points by 50%. Scales and Unrest modify Recruitment Points, too.

Much of the Population (if not all of it) farms. Whether Supplies are bought from the populace or seized is abstracted out, though the Population is left with at least enough to stay alive. Supply yield from the Population is also in tiers:

Forts that aren't under siege also provide Supplies; their Administration value, times 6, divided by the distance from the fort (in provinces) plus 1. For example, A Palisade (15 Administration) provides 30 Supplies to armies two provinces away, calculated by [(6 x 15) / (2 + 1)]. Fort Supplies are not modified by Scales, but Supplies from the Population are!

The smallest unit of Population in this game is 10. That corresponds with 1 point of Unrest (a "filthy brigand or troublemaker"), and with 1 level of Province Defense. You don't get these immediately upon acquiring the province; rather, both maximum Unrest and maximum Province Defense are equal to the local Population divided by 10. There are hard caps for each, however; 100 Province Defense at 1000 Population, and 500 Unrest at 5000.