Difference between revisions of "Population"

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(Strata: Added Assimilation, added from memory.)
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| Alien pops on The Preserve
| Alien pops on The Preserve
| ''Endangered primitive species that are kept preserved in a perfect replica of their natural environment.''
| ''Endangered primitive species that are kept preserved in a perfect replica of their natural environment.''
| [[File:Pop cat assimiliation.png|24px]] Assimilation
| 0
| {{iconify|Machine Intelligence}}
| ''This population is becoming one with the machine.''

Revision as of 01:20, 22 August 2019


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Please help with verifying or updating older sections of this article. At least some were last verified for version 2.3.

This article is for the PC version of Stellaris only.
Demographics in a multispecies empire

Population, also known as Population units or Pop.png Pop, is the center of productivity and political action within the empire. They provide resources by working on districts and buildings, and Influence.png influence if they are part of a specific faction.


Each planet has four variables that determine its demographical direction:

Pop Growth represents the increase in population from natural reproduction and immigration. Any species existing on the planet or which has immigration access to the planet may be selected to grow there. When choosing a species to grow, planets will generally prioritize species that are under-represented on the planet and have citizenship equal to that of the already existing species. Habitability is a major factor in Pop growth. Pops with very low habitability for a planet will only slowly reproduce or migrate to it or may not at all. Species can be chosen manually for Growth if the Population Controls Policy is set to Allowed.

Pop Decline represents the decrease of certain Species on the planet from emigration and purging. Overcrowded planets that have over-represented species will have those species begin to decline in numbers and be replaced by newly growing, under-represented species that have equal citizenship. Purging a particular species will essentially guarantee that species' rapid decline as well as creating massive amounts of emigration in the form of refugees if displacement is used.

Pop Assembly represents a planet's capacity for constructing Trait mechanical.png Mechanical or Auth machine intelligence.png Machine Pops. Job roboticist.png Roboticist Jobs add +2 Monthly Pop Assembly Points and Job replicator.png Replicator Jobs add +1 Monthly Pop Assembly Points. Once 100 points are reached a new robot pop is created on the planet. Non-sentient robotic pops do not migrate but can create overcrowding and unemployment. Templates can always be chosen manually for Assembly.

A planet can have only one growing Pop, one declining Pop and one assembling Pop at any time.


Migration is calculated by subtracting Emigration Push from Immigration Pull, both of which are determined by factors such as housing, stability and unemployment. A planet with more emigration than immigration will have pop decline where the removed pops are distributed among potential immigration targets. Planets with higher immigration pull will receive a greater share of this migration, which is converted directly into pop growth. Signing migration treaties will allow migration to and from other empires and accepting refugees will also create immigration from planets outside the empire borders. When a new planet is colonized existing worlds will get +50 Emigration Push while the new colony will get +100 Immigration Pull.

Growth weight

The exact mechanics by which a new Pop is selected for growing/assembly is not fully known. However a bunch of values could be extracted from the defines file.

Name Value Description
OVERCROWDING_NO_GROWTH_THRESHOLD 1.5 At this pop/housing ratio, pops start declining
OVERCROWDING_DECLINE_THRESHOLD 2.0 At this pop/housing ratio, growth stops entirely
NEW_POP_SPECIES_RANDOMNESS 1.0 The higher this is, the more random species selection of new pops will be
NEW_POP_SAME_SPECIES_WEIGHT 1.0 The higher this is, the more new pops will be weighted by number of same or subspecies pops
NEW_POP_EXACT_SPECIES_WEIGHT 0.5 The higher this is, the more new pops will be weighted by number of exact same species pops
NEW_POP_SLAVERY_WEIGHT 0.5 The higher this is, the more new pops will tend to be balanced between enslaved and non-enslaved species
NEW_POP_SPECIES_DIV 0.5 The higher this is, the more planets will tend to grow species that are underrepresented on the planet
NEW_POP_HABITABILITY_THRESHOLD 0.6 If habitability is under this, apply exponentially increasing penalties to new pop weight
NEW_POP_HOMEWORLD_MULT 2 Pops have increased weight for growing on their homeworld
NEW_POP_ASSEMBLY_TRAIT_MULT 1 Extra weight per trait point for assembled pops
NEW_POP_GROWTH_MOD_MULT 0.66 How much does species growth trait matter for new pop weight
NEW_POP_IMMIGRATION_MOD_MULT 1 How much does species immigration growth trait matter for new pop weight (when there is immigration)
POP_ENSLAVE_MAX_RANK 1 Pops above this stratum rank will not be enslaved from civics, etc
BASE_POP_DECLINE 5 Base decline rate of pops
REQUIRED_POP_DECLINE 100 Required decline to remove a pop
POP_DECLINE_THRESHOLD 3.0 A species will decline when there is another species with a growth priority this many times higher
MAX_EMIGRATION_PUSH 100 Highest possible emigration push value
MAX_GROWTH_FROM_IMMIGRATION 5 Highest possible pop growth due to immigration
MAX_GROWTH_PENALTY_FROM_EMIGRATION 0.95 Maximum pop growth reduction as fraction of base monthly growth


Each pop in an empire has a base Mod pop happiness.png happiness rating. It ranges from 0% to 100% and has a base level of 50%, and together with the Stratum's Mod pop political power.png political power determines the Approval Rating, in addition to the following effects:

  • Each point of Happiness above 50 adds +1% Mod pop government ethic attraction.png Governing Ethics Attraction to free pops and +2% Authoritarian.png Authoritarian Ethics Attraction to slaves.
  • Each point of Happiness below 50 adds −1% Mod pop government ethic attraction.png Governing Ethics Attraction to free pops and +10% Egalitarian.png Egalitarian Ethics Attraction to slaves.
  • Each point of Happiness above 50 gives each pop −0.02 Job criminal.png Crime, up to 0 per pop at 100% Happiness
  • Each point of Happiness below 50 gives each pop +0.02 Job criminal.png Crime, up to +2 per pop at 0% Happiness

Fortunately, there are also many ways to improve happiness in an empire. Planetary edicts, civics, traditions, buildings, planet modifiers and ruler traits can positively affect happiness. Events may have an impact on planetary or empire happiness for a limited time as well.

Approval Rating

Pop Approval Rating is a measure of the population's support towards the empire. It is determined by the average Mod pop happiness.png Happiness of each Stratum, weighted by Mod pop political power.png Political Power.

Approval Rating ranges from 0% to 100% and has a base level of 50%.

  • Each point of Approval Rating above 50% adds +0.6 Stability.png Stability, up to +30 at 100% Approval Rating.
  • Each point of Approval Rating below 50% adds −1 Stability.png Stability, up to −50 at 0% Approval Rating.


Organic pops consume Food.png 1 Food per month. Robots instead consume Energy.png 1 Energy per month. In addition, biological pops that are not part of a Gestalt consciousness.png Gestalt Consciousness empire require a certain amount of Consumer goods.png consumer goods based on their living standards. Synthetics that are given Citizen rights require it as well.


Housing represent the living space available for pops to live comfortably. Housing is primarily provided by districts, with City districts giving more housing than their resource-focused alternatives. Each pop requires 1 unit of housing by default but the housing demands of individual pops can change due to a variety of factors. If the number of pops exceeds the amount of housing it will cause Stability.png stability to drop by and a flat +50 planet emigration push.

As a rule of thumb, each resource district exactly pays for itself in terms of housing, while the pops that work building jobs need city districts (or housing buildings) for their housing, though the capital building provides some buffer before cities are needed. This applies equally to ecumenopolises. The Civic agrarian idyll.png Agrarian Idyll civic gives extra housing to resource districts, allowing the empire to house its pops working building jobs mostly via resource districts.


Amenities represent the infrastructure and jobs dedicated to fulfilling the needs of the population. Individualist empires obtain amenities from a variety of jobs while Gestalt consciousness.png Gestalt Consciousness empires obtain them primarily from Job maintenance drone.png Maintenance Drone jobs. High amenities cause increased Mod pop happiness.png happiness to biological pops and increased stability in Gestalt consciousness.png Gestalt Consciousness empires, while insufficient amenities will lower them.

The formula for extra amenities contributing Mod pop happiness.png happiness is . In other words, it scales from +0% with 0 extra amenities, to +20% with twice as many amenities as necessary.

Total amenities consumed for most organics is population + 5, so if a planet has 27 pops and 13 extra amenities, this produces or Mod pop happiness.png +8% happiness.

All pops get Mod pop happiness.png −2% happiness for each amenity a planet is lacking.

Political power and stratum

Strata represent pops' social classes. The higher a pop's stratum, the more political power they have and the more Consumer goods.png consumer goods and housing they use.

If a pop takes a job above its stratum it will be promoted to the higher stratum. If there are no available jobs of equal or higher Stratum the pop will become unemployed, slowly demoting in stratum and causing Mod pop happiness.png happiness penalties at most levels of living standards.


Stratum Hierarchy position Requirements Description
Pop cat ruler.png Rulers 1 Not Gestalt consciousness.png Gestalt Consciousness The heads of leadership and administration on a planet are vital to its management, uneasy though they may rest.
Pop cat specialist.png Specialists 2 Not Gestalt consciousness.png Gestalt Consciousness These are the workers who provide advanced goods and services in highly-specialized fields.
Pop cat worker.png Workers 3 Not Gestalt consciousness.png Gestalt Consciousness These general laborers form the backbone of industrial and agricultural production, manufacturing and basic services.
Pop cat complex drone.png Complex Drones 1 Gestalt consciousness.png Gestalt Consciousness These drones perform complex tasks that require a high degree of specialization.
Pop cat simple drone.png Menial Drones 2 Gestalt consciousness.png Gestalt Consciousness These drones are tasked with basic industrial production and the provision of general services.
Pop cat pre sapients.png Bio-Trophies 1 Biological species in a Civic machine servitor.png Rogue Servitor empire Sheltered from harm, suffering, and even their own self-destructive tendencies, Bio-Trophies want nothing; their every need tended to and provided by a team of tireless servitors.
Pop cat criminal.png Criminals 0 High Job criminal.png Crime Career criminals living beyond the reach of the law.
Pop cat criminal.png Deviant Drones 0 High Job criminal.png Deviancy in Auth hive mind.png Hive Mind empires Deviants who have rejected the will of the Hive Mind.
Pop cat criminal.png Corrupt Drones 0 High Job criminal.png Deviancy in Auth machine intelligence.png Machine Intelligence empires Corrupted drone units operating outside the parameters set by the core intelligence.
Job purge.png Undesirables 0 Undesirables citizenship Those that have no place in society will be removed from it. Permanently.
Pop cat pre sapients.png Pre-sapients 0 Pre-sapients Simple beasts to an extent, and yet their behavior betrays some degree of intelligence...
Pop cat precursor.png Precursors 1 Fallen Empire The dominant species in an ancient Fallen Empire, these precursors live among technological marvels that the younger races can only dream of.
Pop cat xeno ward.png Primitives 2 Alien pops on The Preserve Endangered primitive species that are kept preserved in a perfect replica of their natural environment.
24px Assimilation 0 Auth machine intelligence.png Machine Intelligence This population is becoming one with the machine.


Xenophobe.pngFanatic Xenophobe.png Xenophobe and Authoritarian.pngFanatic Authoritarian.png Authoritarian empires can give to organic alien species the Slavery citizenship, with its effect dependent on the Slavery Type species right.

Authoritarian.png Authoritarian empires have access to the Civic slaver guilds.png Slaver Guilds or Civic indentured assets.png Indentured Assets civics, which will enslave up to 40% of pops on every planet regardless of citizenship if there are not enough alien pops with Slavery citizenship to fill the quota.

Robots are automatically enslaved if the Tech synthetic workers.png Synthetics technology is researched and Artificial Intelligence Policy is set to Servitude. In Synthetic Dawn.png Synthetic Dawn this may cause an AI rebellion.

Enslaved pops also use only Amenities.png 0.75 amenities and Housing.png 0.75 housing instead of 1, and can be further reduced if the Slavery type is Servitude or Livestock. They also get -50% Mod pop resettlement cost mult.png Resettlement Cost. Enslaved pops cannot join Factions and have only 25% Mod pop political power.png Political Power, or 0% if a Slave Processing Facility is present on the planet. However they can still increase Job criminal.png Crime if they're too unhappy.

Low Stability.png Stability is more dangerous when enslaved pops are present on a planet. Normally dangerous events can only occur if it's lower than 25 but if any pop is enslaved it must be kept above 40.

Slave Output can be affected by the following:

Source Slave Output
Civic slaver guilds.png Slaver Guilds civic +10%
Civic indentured assets.png Indentured Assets civic +10%
Leader trait iron fist.png Iron Fist governor trait +10%
Agenda Slave Optimization agenda +10%
Tradition domination vassal acculturation.png Workplace Motivators tradition +5%
Building Slave Processing Facility building +5%
Pm slave riots.png Slave Riots planet modifier -100%

Ethics attraction modifiers

Ethics divergence is where a pop or group of pops decide to follow a different ethic than the general population. A materialist pop may decide to follow a more spiritual path and a pacifist culture might decide that peace is the path of the weak.

Each pop in an empire will only embrace a single, non-fanatic ethic. At the start of the game, the population will be made of the ones that were picked. As population expands and eventually is divided over various planets and sectors, certain segments may decide to adopt values that are different from the core values of the species due to various circumstances in and around the empire.

Each ethic has a certain attraction value attached for all pops, depending on both the empire's situation and their own. For example,

  • enslaved pops tend to become more egalitarian;
  • fighting a lot of wars will increase the attraction for militarism across the entire empire.

The exact values and options that influence the attraction levels of certain ethics can be found at ethics attraction.

The attraction factors of ethics can be amplified by certain actions such as enacting policies or having traits. Governing ethics attraction can be modified by policy, edict, or through promoting or suppressing political fraction.

Having a positive ethics attraction effect will let all actions that increase attraction to the government ethics result in even more attraction, and negative amounts will be decreased. With a modifier of 50%, an action that would increase attraction by 2 would instead increase by 3.

Source Bonus
Empire capital.png Empire Capital +100%
Menu icon policies and edicts.png Hearts and Minds ambition +100%
Ap one vision.png One Vision ascension perk +50%
Menu icon policies and edicts.png Information Quarantine edict +50%
Tradition harmony the greater good.png The Greater Good harmony tradition +25%
Sb deep space black site.png Deep Space Black Site starbase building +25%
Trait primitive.png Conservative species trait +25%
Conformists.png Conformists species trait +20%
Leader trait psionic chosen one.png Chosen One ruler trait +20%
Leader trait psionic leader.png Psychic ruler trait +10%
Civic imperial cult.png Imperial Cult civic +10%
Deviants.png Deviants species trait −15%


Sentient Robot

Robots are artificial pops and can be constructed once the required technology becomes available. They have the Trait mechanical.png Mechanical trait, giving them Mod habitability.png +200% habitability on any planet. Robots can be given new traits via robo-modding and the template with the highest number of used trait points will be built by default. A different template can be specified for each planet.

The jobs a robot can have are limited by the highest robot technology researched. If an empire researches the Tech synthetic workers.png Synthetics technology, robots can be given sentience, which lets them be affected by Mod pop happiness.png happiness and have ethics.

Tech level Maximum stratum Can colonize Sentient
Tech robotic workers.png Robotic Workers Pop cat worker.png Worker (except Job technician.png Technician and Job clerk.png Clerk) No.png No.png
Tech droid workers.png Droids
  • Pop cat specialist.png Specialist (except Job researcher.png Researcher and Job culture worker.png Culture Worker) if AI policy is set to Servitude
  • Pop cat worker.png Worker if AI policy is set to Outlawed
Yes.png No.png
Tech synthetic workers.png Synthetics
  • Pop cat ruler.png Ruler if AI policy is set to Citizen Rights
  • Pop cat specialist.png Specialist if AI policy is set to Servitude
  • Pop cat worker.png Worker if AI policy is set to Outlawed
Yes.png No.png if AI policy is set to Outlawed

Yes.png if AI policy is set to Servitude or Citizen Rights

Robots without Citizen Rights require 50% less Housing.png housing and Amenities.png amenities and do not need Consumer goods.png consumer goods. If a planet with sentient robots is captured by an empire that doesn't have the Tech synthetic workers.png Synthetics technology, they lose their sentience, and if a planet with non-sentient robots is captured by an empire that has the Tech synthetic workers.png Synthetics technology and does not have the Outlawed Artificial Intelligence policy, they are immediately given sentience. Spiritualist.pngFanatic Spiritualist.png Spiritualist empires cannot give them citizen rights.

As long as an empire with the Tech sentient ai.png Positronic AI technology has the Artificial Intelligence policy set to Servitude, there is a risk of them starting the AI rebellion event chain. See AI rebellion for details.


Purges represent the systematic elimination of specific pops or entire species from an empire and can be done on a per pop or species basis.

Targeted pop purging still requires applying the species-wide slavery at minimum and it is limited to a basic extermination, although without production penalty. Gestalt consciousness.png Gestalt Consciousness can purge their pops of any composition freely, with exception of Bio-Trophies.

Species-wide purging is done by setting the species' citizenship to Undesirables. Gestalt consciousness.png Gestalt Consciousness pops in empires of different authority are automatically set as Undesirables too. Therefore gaining planets from a Auth hive mind.png Hive Mind empire means that the planet will be lost when it is empty of pop if there is not at least 1 Pop of the conquering empire's species on it. There are also four special cases:

  • Pre-Sapients can only be purged if the Pre-Sapients policy is not set to Protected and are automatically purged if set to Extermination.
  • Robots are automatically purged if the Robotic Workers policy is set to Outlawed.
  • Synthetics can only be purged if the Artificial Intelligence policy is not set to Citizen Rights.
  • Empires with the Evolutionary Mastery ascension perk can change the citizenship of hive mind pops to Assimilation, which prevents them from being purged.

Having any pops marked as undesirable is a negative issue for Xenophile factions. Depending on the purge type, a timer will be started for all pops (see Purge time below). When the time runs out, the purge is completed: all remaining pops of that species will be removed from the empire's planets. Unless the purge type is Neutering or the pop was pre-sentient, robotic or a Gestalt Consciousness, an Diplomacy opinion.png opinion penalty will be applied to all other regular empires based on the number of pops purged, depending on various modifiers. If the empire has the same primary species as the purged pops, the penalty is always −25 per purged pop. These stack up to −1000, making genocide a dangerous approach.

There are multiple types of purges available, determined by the Purge Type species right.

Type Monthly decline speed Effects Diplomacy opinion.png Loss Generates refugees Requirements Description DLC
Displacement 0.25 per planet
  • Mod pop happiness.png Happiness −30%
  • Mod pop housing usage.png Pop housing usage −50%
no 100%
  • No.pngCivic fanatic purifiers.pngCivic devouring swarm.pngCivic machine terminator.png Genocidal empire
  • No.pngHive-minded.png Hive-Minded or Auth machine intelligence.png Machine Unit species
  • No.pngTrait cybernetic.png Cybernetic species if empire is Civic machine assimilator.png Driven Assimilator
  • No.pngTrait mechanical.png Mechanical species, unless the Pops are sapient
It's not that we drive them from their homes. Their homes are simply no longer theirs.
Extermination 1 per planet Mod pop happiness.png Happiness −1000% yes 5% No.pngCivic devouring swarm.png Devouring Swarm The extermination squads are efficient. The dissolution of entire populations naturally takes time, but they get the job done.
Neutering 0.1 per planet
  • Mod pop happiness.png Happiness −20%
no 0%
  • No.pngGestalt consciousness.png Gestalt Consciousness
  • No.pngHive-minded.png Hive-Minded species
  • No.pngTrait mechanical.pngAuth machine intelligence.png Robotic species
Think of it as a phasing-out of a people. Our nation goes to meet the future, only some will not be with us. Utopia.png
Forced Labor 0.5 per planet
  • Mod pop happiness.png Happiness −1000%
  • Food.png Food +3
  • Minerals.png Minerals +3
yes 33%
  • No.pngGestalt consciousness.png Gestalt Consciousness
  • No.pngHive-minded.png Hive-Minded species
  • No.pngTrait mechanical.pngAuth machine intelligence.png Robotic species
With this final sacrifice, they will at least have been of some use. Utopia.png
Processing 0.5 per planet
  • Mod pop happiness.png Happiness −1000%
  • Food.png Food +6 if species is organic
  • Minerals.png Minerals +4 if species is Trait lithoid.png Lithoid
  • Alloys.png Alloys +3 if species is Trait mechanical.pngAuth machine intelligence.png Robotic
yes 20%
  • No.pngAuth machine intelligence.png Machine Intelligence
  • No.pngHive-minded.png Hive-Minded species
  • No.pngTrait mechanical.pngAuth machine intelligence.png Robotic species, unless empire is Civic devouring swarm.png Devouring Swarm
It is a sad but inescapable fact that some are destined to simply fuel the ambitions of their betters. Utopia.png
Chemical Processing 0.5 per planet
  • Mod pop happiness.png Happiness −1000%
  • Energy.png Energy +6
yes 20%
  • Auth machine intelligence.png Machine Intelligence
  • No.pngTrait mechanical.pngAuth machine intelligence.png Robotic species
They will soon attain a more efficient form. Synthetic Dawn.png
Necrophage 0.25 per planet
  • Mod pop happiness.png Happiness −50%
  • Time Purged Pops are changed to primary species
yes 10%
  • Origins necrophage.png Necrophage origin
  • No.pngTrait mechanical.pngAuth machine intelligence.png Robotic species
Only the strongest may survive in a hostile galaxy. This way their journey may continue. Necroids.png


Human Refugees

Pops from other empires may flee to escape purges, slavery, resettlement, crisis bombardment or as a result of land appropriation. Whether another empire is willing to accept those fleeing depends on its Refugees policy. An empire can choose to accept other species with open arms, allowing refugee pops to freely move into their empire; be more restrictive and accept only those pops that the empire has deigned to grant citizenship; or simply shut down acceptance of refugees altogether.

Refugees can be used to help grow an empire as well as gain access to new species as persecuting empires are unlikely to favor migration treaties in the first place. However, refugees may introduce ethics which are radically different to an empire's. Accepted refugee pops will get a temporary Mod pop happiness.png +20 happiness.

Pops with the Hive-minded.png Hive-Minded or Nerve Stapled.png Nerve Stapled traits cannot become refugees.


Game concepts
Governance EmpireEthicsGovernmentCivicsPoliciesEdictsLeaderFactionsPopulationSpecies rightsEconomyTechnologyTraditionsCrime
Exploration ExplorationMapSpeciesAnomalyEventsFTLFallen empirePre-FTL speciesPrecursorsSpaceborne aliens
Colonization ColonizationCelestial bodyPlanetary featuresPlanetary managementDistrictsBuildingsShipStarbaseMegastructures
Diplomacy DiplomacyTradeSubject empireFederationsGalactic communityAI personalities
Warfare WarfareSpace warfareLand warfareShip designer
Others TraitsTerraformingPop modificationSlaveryCrisisPreset empiresAI playersEaster eggs