data/export_descr_character_traits.txt already has this following trait configured
Code:
;------------------------------------------
Trait AIGovernor
Characters family
Hidden
Level AIGovernor1
Description Hidden_desc
EffectsDescription Hidden_effects_desc
Threshold 1
Effect Construction 70
Effect Fertility 1
Effect TaxCollection 40
Effect Law -1
; Effect Trading 50
; Effect Farming 2
Effect Defence 1
Level AIGovernor2
Description Hidden_desc
EffectsDescription Hidden_effects_desc
Threshold 2
Effect Piety 1
Effect Construction 80
Effect Fertility 2
Effect Squalor -1
Effect TaxCollection 60
; Effect Trading 80
; Effect Farming 3
Effect Law -1
Effect PublicSecurity 1
Effect Defence 2
Level AIGovernor3
Description Hidden_desc
EffectsDescription Hidden_effects_desc
Threshold 3
Effect Piety 1
Effect Construction 90
Effect Fertility 3
Effect Squalor -2
Effect TaxCollection 80
; Effect Trading 100
; Effect Farming 4
Effect Law -2
Effect PublicSecurity 2
Effect Defence 3
As you can see, the three different levels, which are triggered by increasing levels of campaign difficulty, give varying bonuses to squalor. Chances are, you're playing on medium difficulty which means no squalor bonus. Or the AI settlement isn't governed by a character. Either way, in order to further boost population growth, do these steps
1. Make a backup of data/export_descr_character_traits.txt
2. Add:
to the AIGovernor1 effects. Then, increment the squalor bonus by 1 for AIGovernor2 and 3. So it would be -1 for level 1, -2 for level 2, and -3 for level 3. The reason for this buff being small is that AI cities already grow pretty fast if governed by a character, and on harder difficulties. Buffing the squalor even more would mean that every governed AI city would become a Huge City by turn 100 or something crazy like that. So keep it small