Population Units

A city's population consists of population units, which can be assigned as workers to produce FIDSI resources every turn. The amount of each FIDSI resource produced by a worker in a city starts at 4, with the exception of Influence, which starts at 2, due to the City Hall improvement automatically built when founding a city. Worker production can be increased with city improvements, empire plan policies, and Hero Skills, Capacities, and Accessories.

Growth, Consumption, and Starvation
For all empires but the Broken Lords (see below), the generation of population units is organic. When positive, a city's total Food output is added to its growth stock every turn. When the growth stock reaches its upper limit, a new population unit is generated. This upper limit is determined by the equation 5 * 2.75, so a city with 3 needs to have a stock of ~103  for the fourth  to appear.

Additionally, each population unit consumes 2 every turn, and a negative total Food output will subtract from the city's growth stock. When the growth stock reaches its lower limit (equal to the upper limit needed to get the current population), a population unit is removed from the city. Note that a city's population can never be reduced below 1 through starvation. Additionally, when producing a Settler, Food output is reduced to zero if you would otherwise have positive output. Producing a Settler with negative Food output will not increase your output to zero. Producing a Settler removes one population unit.

Broken Lords Population Units
Population unit mechanics work differently for the Broken Lords, as they cannot produce or consume Food. Population units can only be generated by buying out a population increase with Dust in the city screen. Population units are not generated organically by the Broken Lords and cannot be assigned as Food workers. Because of the lack of a Food growth stock, they are also immune to starvation.

Worker Production
Worker production can be increased in a variety of ways, but it's important to remember that these increases only apply to population units assigned as workers to the appropriate resource. A city improvement that increases Food production for each worker would have no effect on population units assigned as Dust workers, only those assigned as Food workers.

City Improvements
To simplify this section, and because some city improvements provide bonus "per " output for multiple resources, the following table will show by how much each of the city improvements increases the given resource per unit of population. Additionally, many of the listed improvements have other effects or conditions to be built not listed here.

One improvement not listed on the table is Defensive Wards, which is something of a special case. While Defensive Wards also has a "per " effect, it increases a city's Fortification by 30  per  rather than any of the FIDSI resources, and also doesn't require the  to be assigned to any specific role for the effects to come into play; if a city has 10  and it builds this, it will get a bonus of 300  regardless of how those population units are assigned.

Empire Plan
By setting the "Economy and Population" branch of the Empire Plan to its first tier, all cities in your empire get +3 per.

Heroes
Heroes have three main avenue for increasing the "per " output of a city: Capacities, Skills, and Accessories.

Capacities
With the exception of the Slavery capacity, all capacities that increase the "per " output of a city have the name "[Resource] Efficiency X", where the resource is one of the FIDSI resources, and X is a number 1 through 3 that determines the effectiveness of the capacity. As an additional note, the Sway of the Master can be equipped on heroes to give them the Slavery capacity.

Skills
The only Hero skill that increases the "per " output of a city is the Cultists Hero skill "Impassioned Preacher", which provides +1 per for each of the FIDSI resources on the city per level of the skill, up to 3.

Accessories
The accessories that can be equipped to a Governor to increase a city's "per " output are the Tomes made of Titanium, Glassteel , Adamantian , and Palladian , which focus on Science , Dust , Industry , and Food respectively. They all require researching a specific technology to unlock.