Please help with verifying or updating older sections of this article.
At least some were last verified for version 1.29.
Negative overextension modifiers
Overextension is a game mechanic modelling the issues caused by rapid expansion.
Each non-core province causes overextension equal to 80% of its development. For example, a province with a development of 10 will add 8% overextension regardless of how big the country is. Overextension has no cap; it can potentially go far beyond 100% and its penalties will continue to increase.
Any province which was settled by colonization doesn't give overextension even if it is conquered by another country after the colony finishes. This doesn't include provinces settled by native tribes.
These are the effects at 100% overextension:
 |
−100%.00 |
Trade power abroad
|
 |
+50%.00 |
Stability cost modifier
|
 |
+50%.00 |
Mercenary cost
|
 |
−2.00% |
Diplomatic reputation
|
 |
−50%.00 |
Improve relations
|
 |
+5.00% |
National unrest
|
 |
+0.50% |
Yearly corruption
|
 |
+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:
|
|
Traditions
|
Ideas
|
Bonuses
|
Policies
|
| +5%
|
|
- Bharathi idea 6: Brahmin Administration
- Great Qing idea 5: Chinese Laws
- Great Yuan idea 6: Sino-Mongol Administration
- Imperial German idea 6: Reichstag
- Roman idea 6: Imperial Bureaucracy
- Scandinavian idea 2: Unified Scandinavia
|
|
—
|
Further modifiers:
|
Type
|
| +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”
|
| +5% |
holding  Alhambra at  Magnificent level (only with  )
|
| +2.5%
|
Political Absolutism government reform
|
A custom nation can have a national idea of up to +10% administrative efficiency.
Mission reward modifiers:
- ↑ 20 years with the
Rule Britannia DLC and 30 years without it
Overextension is a game mechanic modelling the issues caused by rapid expansion.
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%.
Alhambra at 
Magnificent level (only with 
Invade China (Horde mission tree)
