编辑“人口”（章节）

== Demographics ==
Each planet has four variables that determine its demographic direction. A planet can have only one growing pop, one declining pop and one assembling pop at any time.

=== Pop growth ===
[[File:Update 3 growth surface plot.png|right|thumb|300px|Growth as a function of planet capacity and population]]
{{icon|growth speed}} '''Pop growth''' represents the increase in population from natural reproduction and immigration. A new pop appears after <math>100 + (\text{growth required scaling} \cdot {\text{total empire population}})</math> growth points have been accumulated; the [[Game settings#Game Details|growth required scaling]] is a game setting. The base growth rate is determined by the number of pops on the planet along a [[wikipedia:logistic curve|logistic curve]] determined by the {{icon|planet capacity}} [[Celestial body#Planet capacity|planet capacity]], then pop growth modifiers are applied, and lastly pop growth from immigration/emigration is added/subtracted. The [[Game settings#Game Details|logistic growth ceiling]] game setting determines the maximum base growth.

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. If immigration access is lost to all planets containing the currently selected species, a new species will be selected and all existing growth progress will be erased. Species can be chosen manually for growth if the Population Controls policy is set to ''Allowed''. 

{{iconify|Habitability}} is an important pop growth modifier. Pops with very low habitability for a planet will only slowly reproduce or migrate to it or may not at all.

Pop growth stops when a planet is 15% overcrowded and has 5 pops without housing. Pops start to decline when a planet is 25% overcrowded.

{{icon|planet capacity}} [[Celestial body#Planet capacity|Planet capacity]] is capped at 500, regardless of free housing or unblocked districts. However, pops over 500 will not stop growing or decline until required housing exceeds available housing by 15% or 25%, as normal.

{| class="mildtable" 
|+ Base population growth formulas
|-
! Condition
! Formula
|-
| style="border-right:solid thin #ddd; padding-right:0.5em" | <math>\frac{{\text{planet capacity}}}{2} > {\text{planet population}}</math>
| <math>\text{total base growth} = 3 \cdot \max (0.125 \cdot (\text{population} - \frac{\text{population}^2}{\text{planet capacity}} - 1) , 1)</math>
|-
| style="border-right:solid thin #ddd; padding-right:0.5em" | <math>\frac{{\text{planet capacity}}}{2} \le {\text{planet population}}</math>
| <math>\text{total base growth} = 3 \cdot 0.125 \cdot (\text{population} - \frac{\text{population}^2}{\text{planet capacity}} - 1)</math>
|}

Total base pop growth is between 0.3 and <math>(\text{logistic growth ceiling} \cdot 3)</math> (default 4.5) growth per month. Pop growth modifiers, including habitability penalties, are then applied, and then population growth from immigration/emigration is added/subtracted.

==== Migration ====
[[File:Species_right_migration_controls.png|Migration|x24px]] '''Migration''' is calculated by subtracting '''emigration push''' from '''immigration pull''', both of which are determined by factors such as {{iconify|housing}}, {{iconify|stability}} and {{icon|unemployed}} unemployment. A planet with more emigration than immigration will have its {{iconify|growth speed}} lowered and the amount lowered will be added to potential immigration targets. Planets with higher immigration pull will receive a greater share of this migration, which is converted directly into pop growth. Signing a {{iconify|migration treaty}} will allow migration to and from another empire's planets. A newly colonized planet gains {{green|+100}} immigration pull and divides a total of {{yellow|+50}} emigration push between all developed planets, until {{icon|time}} 15 years have passed or the colony has 10 {{iconify|pops}}.

==== Growth weight ====
The exact mechanics by which a new pop is selected for growing/assembly is not fully known. However a bunch of values can be extracted from the {{path|common/defines/00_defines.txt}} file.
{| class="mildtable"
|-
! Name !! Value !! Description
|-
| New_Pop_Species_Randomness || 0.5 || 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 || 0.25 || The higher this is, the more new pops will tend to be balanced between enslaved and non-enslaved species
|-
| New_Pop_Species_Div || 0.05 || The higher this is, the more planets will tend to grow species that are underrepresented on the planet
|-
| New_Pop_Habitability_Threshold || 0.75 || 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_Growth_Mod_Mult || 0.33 || How much does species growth mod trait matter for new pop weight
|-
| NEW_POP_Immigration_Mod_Mult || 1 || How much does species immigration growth mod trait matter for new pop weight (when there is immigration)
|-
| Pop_Decline_Threshold || 3.0 || A species will decline when there is another species with a growth priority this many times higher
|}

=== Pop assembly ===
'''Pop assembly''' represents a planet's capacity for constructing {{iconify|Mechanical}}, {{iconify|Machine}}, or biological pops. Pop assembly can be either robotic or biological at a given time; both cannot be produced simultaneously. Once <math>100 + (0.25 \cdot {\text{total empire population}})</math> assembly points are reached, a new pop is created on the planet. Non-sapient robotic pops do not migrate but can create overcrowding and unemployment. The constructed template is the one with the highest number of used trait points, but can always be changed manually; unlike choosing a species to grow, this does not cause a penalty to assembly speed.

[[File:Pop assembly.png|24px]] Robotic pop assembly is affected by traits and other modifiers.

[[File:Pop assembly organic.png|24px]] Organic pop assembly is not affected by any traits or modifiers except for the following:
* {{green|+5%}} per {{iconify|Medical Worker}} Job
* {{red|−25%}} from {{iconify|Lithoid}}
* {{red|−75%}} from {{iconify|Necrophage}}

{| class="mildtable"
! Assembly type !! [[File:Mod_planet_pop_assembly_add.png|24px|Monthly pop assembly points]] !! Source !! DLC !! Other requirements
|-
| rowspan=2 | [[File:Pop assembly.png]] Robotic pop assembly 
| align=center | {{green|+2}} || {{iconify|Roboticist}} jobs ||  || {{iconify|Robotic Workers|24px}} technology
|-
| align=center | {{green|+1}} || {{iconify|Replicator}} jobs || align=center | {{icon|snd}} || {{iconify|Machine Intelligence}} authority
|-
| rowspan=5 | [[File:Pop assembly organic.png]] Organic pop assembly 
| align=center | {{green|+2}} || {{iconify|Spawning Drone}} jobs || align=center | {{icon|utp}} || {{iconify|Hive Mind}} authority
|-
| align=center | {{green|+2}} || {{iconify|Reassigner}} jobs || align=center | {{icon|nec}}{{icon|mgc}} || {{iconify|Permanent Employment}} civic
|-
| align=center | {{green|+3}} || {{iconify|Clone Vats|24px}} buildings || align=center | {{icon|utp}} || {{iconify|Engineered Evolution}} ascension perk
|-
| align=center | {{green|+2}} to {{green|+15}} || [[File:Building ancient relics.png|24px|link=Buildings#Ancient Clone Vat]] Ancient Clone Vat buildings || align=center | {{icon|hum}} || {{iconify|Clone Army origin}}
|-
| align=center | {{green|+0.02}} || {{icon|budding}} Each pop with the Budding trait || align=center | {{icon|plantoids}} || 
|}

=== Pop decline ===
'''Pop decline''' represents the decrease of certain species on the planet due to purging or severe overcrowding. A pop will disappear after 100 decline points have been accumulated. By default, decline rate is {{red|−5}} decline points per month. 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 cause that species to decline more rapidly depending on the purge type; the decline factor from purging overrides natural decline factors.

=== Resettlement ===
Resettlement is the process of pops moving from one planet to another, more desirable one.

==== Automatic resettlement ====
Sapient, unemployed, free pops have a chance (each month) to automatically resettle to another planet with available jobs and housing and suitable habitability. If a {{iconify|Slave Processing Facility|24px}} is active on the planet, enslaved pops and robots in servitude are also eligible.

{{iconify|Migration controls}} will prevent this (except for sapient robots). Empires that outlaw slavery (and hence the slave processing facility) cannot enable automatic resettlement for robots in servitude.

A {{iconify|Transit Hub|24px}} starbase building will increase the monthly chance of a pop automatically resettling.

==== Forced resettlement ====
If the empire's {{icon|policy}} [[Policies#Resettlement|Resettlement]] policy allows it, forced resettlement will instantly move a pop from one planet to another. This costs a base amount of {{iconify|energy}} and {{iconify|unity}} determined by the pop's category, which may be reduced by additional modifiers.

{{box wrapper}}
{| class="mildtable plainlist sortable"
! rowspan="2" | Pop category
! rowspan="2" | Allowed?
! colspan="2" | {{icon|resettlement cost}} Base cost
|-
! {{icon|Energy}}
! {{icon|Unity}}
|-
| {{iconify|Ruler}}      || {{iconify|Policy}} || align=center | {{red|500}} || align=center | {{red|50}}
|-
| {{iconify|Specialist}} || {{iconify|Policy}} || align=center | {{red|250}} || align=center | {{red|25}}
|-
| {{iconify|Worker}}     || {{iconify|Policy}} || align=center | {{red|100}} || align=center | {{red|10}}
|-
|
* {{iconify|Complex Drone}}
* {{iconify|Menial Drone}}
| {{icon|yes}} Always || align=center | {{red|100}} || align=center | {{red|10}}
|-
| {{iconify|Slave}}      || {{iconify|Policy}}  || align=center |  {{red|50}} || align=center | {{green|0}}
|-
| {{iconify|Bio-Trophy}} || {{icon|yes}} Always || align=center | {{red|100}} || align=center | {{red|25}}
|-
| 
* {{iconify|Purging}}
* {{iconify|Assimilation}}
| {{icon|yes}} Always || align=center | {{red|100}} || align=center | {{green|0}}
|-
| [[File:Job_servant.png|24px|link=Policies#Servitude]] Robotic servitude
<!-- shackled (yes)  = mechanical + not full rights; non sapient (policy) = no synths tech or AI outlawed -->
| {{icon|yes}} Always || align=center | {{red|100}} || align=center | {{green|0}}
|-
| {{icon|Criminal}} Subversive || {{icon|no}} Never || colspan="2" align=center | n/a
|}

{| class="mildtable sortable"
! rowspan="2" | Modifier source
! colspan="2" | {{icon|resettlement cost}} Cost
|-
! {{icon|Energy}}
! {{icon|Unity}}
|-
| {{icon|edict}} Evacuation Protocols edict
| colspan="2" align=center | {{green|−50%}}
|-
| {{tradition|adaptability|Appropriation|iconify}} tradition
| colspan="2" align=center | {{green|−33%}}
|-
| {{tradition|versatility|Operational Proxies|iconify}} tradition
| colspan="2" align=center | {{green|−33%}}
|-
| {{iconify|Corvee System}} civic
| align=center | '''+0%'''
| align=center | {{green|−100%}}
|-
| {{iconify|Subsumed Will}} civic
| align=center | '''+0%'''
| align=center | {{green|−100%}}
|-
| {{iconify|OTA Updates}} civic
| align=center | '''+0%'''
| align=center | {{green|−100%}}
|-
| {{iconify|Starborn}} trait
| colspan="2" align=center | {{green|−25%}}
|-
| {{iconify|Nomadic}} trait
| colspan="2" align=center | {{green|−25%}}
|-
| {{iconify|Sedentary}} trait
| colspan="2" align=center | {{red|+25%}}
|}
{{end box wrapper}}