Each non-core province, with the exception of colonies, causes overextension equal to province development. For example, a province with a development of 24 will add 24% overextension regardless of how big the state is. Note that overextension has no cap; it can potentially go far beyond 100% and its penalties will continue to increase.
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These are the effects at 100% overextension:
|−100%||Trade power abroad|
|+50%||Stability cost modifier|
|+0.50||Secretariat faction influence|
|+0.50||The guilds influence|
In addition, the AI will view overextended countries more negatively, and will be more likely to either declare war itself, or form a coalition against that country.
At over +100% overextension:
- Monthly chance of increasing progress to each uprising is multiplied by more than 3×, growing with higher overextension (though still capped at 75%.)
- Various nasty events will trigger, doing things such as lowering stability or hurting trade. The base frequency is one bad event per year, with the time decreasing with higher overextension. Members of the Holy Roman Empire will be reluctant to support reforms while the Holy Roman Emperor is overextended.
These penalties combined can really destabilize a country. It is advised not to go above 100% overextension as the severity of the risks rises dramatically.
Overextension can be reduced by:
- Coring provinces, which takes time and administrative power
- Selling or granting non-cored provinces to subjects to let the subjects core them (you may be able to annex them later)
- Selling provinces to other nations
- Releasing a vassal that has a core on it
- Making a new client state from the non-cored provinces ( Art of War only)
Note that a country will only accept buying a province if they have a core on the province, or it has the same culture group and religion. They also should not be overextended themselves.
Administrative efficiency directly reduces core creation and diplo-annexation costs. It also reduces the impact of province development on overextension, warscore cost and aggressive expansion, allowing for much larger territories to be conquered at once. All effects of administrative efficiency are capped at 90%.
Ideas that boost efficiency:
|+10%||administrative technology level 17|
|+10%||administrative technology level 23 (cumulative)|
|+10%||administrative technology level 27 (cumulative)|
|+0.3%||Per point of absolutism or revolutionary zeal (max +30% )|
|+5%||Age of Absolutism splendor ability “Administrative Efficiency”|
A custom nation can have a national idea of up to +10% administrative efficiency.
Mission reward modifiers:
|+10%||20 years||Invade China (Horde mission tree)|
|+10%||Permanent||Viceroyalty Deccan event choice (Mughals mission tree)|
|+5%||Permanent||Glory to von Habsburg! (Austrian mission tree)|
|+5%||Permanent||Break the Chains (Dithmarscher mission tree)|
|+5%||Permanent||French Revolution (French mission tree)|
|+5%||Permanent||Kaiserreich (German mission tree)|
|+5%||Permanent||Carolingian Empire (Lotharingian mission tree)|
|+5%||Permanent||German Confederation (Prussian/Brandenburgian mission tree)|
|+5%||Permanent||Russian Revolution (Russian mission tree)|
|+5%||Permanent||Alpine Powerhouse (Savoyard/Sardinia-Piedmont mission tree)|
|+5%||20/30 years||Subiaco Press (Papal mission tree)|