This article has been verified for the current version (1.30) of the game.
Local autonomy is a characteristic of a province, reducing its utility. It shows how much the current province is "tied" to the current government, and how much it really is part of the country as opposed to favoring self-rule (Although the government considers a cored province part of a nation, the local populace might not consider itself part of the government/nation).
A province at 50-60% autonomy for example, could be a province where the government has little to no power and leaves all its issues to the local populace. However, in return, that province will offer less to the government itself as shown below. Its effects make the integration of conquered provinces more gradual and offer the ruler a choice in its pace, and simulate the limits to central rule in faraway overseas provinces.
Local autonomy applies multiplicatively, rather than additively. This majorly impacts how local autonomy affects a nation. A +50% manpower boost in a 50% autonomy province would thus yield an increase of only 25% of the base value.
It is advised to keep autonomy at a low point, because it affects most of the output of a province.
Each percentage point of local autonomy has the following effects on the province:[1]
Multiplicative effects:
−1.0%
Local manpower modifier
−1.0%
Local sailors modifier
−1.0%
Local tax modifier
−1.0%
Local production efficiency
−0.5%
Local trade power
−1.0%
Land force limit modifier
−1.0%
Naval force limit modifier
In trade company provinces the following effects are used instead:[2]
Multiplicative effects:
−1.0%
Local manpower modifier
−1.0%
Local sailors modifier
−1.0%
Local tax modifier
−0.5%
Local production efficiency
−1.0%
Land force limit modifier
Additionally in both trade company and non-trade company provinces:
In provinces with a minimum autonomy modifier, there is also a “hidden” level of autonomy that could be lower. This “hidden” autonomy declines over time, although it is not displayed in the game. For example, the player conquers a province where the player has a claim, and the provinces initial autonomy (before conquering) was below 40%. Since the player has a claim on that province, real (but “hidden”) autonomy is set to 40%. But if the province is a territory, its minimum autonomy will be 75%.
NB: If the player chooses to raise autonomy (manually OR by event) while the province is still a territory, from 90% → 100% then the virtual autonomy will be raised to 100% too! If the player waits until the province is cored and made a state, its minimum autonomy floor will be removed, lowering the province autonomy to its virtual value, which is either 40% if there is a claim, and 50% if there isn't a claim. Now the player can raise autonomy to 65%/75% without suffering an extra +10% autonomy unspoken "penalty".
If the hidden local autonomy of a province is currently 75%[4] or lower, the province owner may increase its local autonomy level by +25% in exchange for -10 unrest. Local autonomy can also be decreased by -25% at the cost of +10 unrest provided it's not below 10% autonomy and not already at the minimum autonomy of the province. The decision to change autonomy levels will be in effect for 30 years, during which time the autonomy cannot be actively adjusted again. This cooldown may be reduced by 50% with the ‘Efficient Autonomy’ ability during the ‘Age of Absolutism’. (Note: Ongoing cooldowns are not affected.) If a province changes owners, both the modifier from adjusting autonomy and the timer are reset.