Court level is a measure of the prestige of your court and thus your country. It can be visualized with the court decision in the “State” menu.
The court level changes according to its total endowment which decreases by 5% each year. This can be affected with the monthly budget and the “one-time stipend” action.
|Stability Increase Interval||+10%||+5%||-5%||-10%||-15%||-20%|
|Liberty Desire in Subjects||+20%||+5%||-5%||-10%||-15%||-20%|
|Moral of Armies||0||0||0||+2.5%||+2.5%||+5%|
|Moral of Navies||0||0||0||+2.5%||+2.5%||+5%|
Court price calculation Edit
You lose 5% of your court level every year, and 10% of your current endowment is put towards paying for the court each year.
The endowment is increased by what you pay directly plus half of your provincial capital buildings' upkeep every year.
The cost to increase the court level (so how many ducats you have to pay to get one court level point) is multiplied by your non-overseas upper class pops (/10,000), as well as half of your subjects' non-overseas upper class pops. In other words, it's multiplied by ~5% of your population (/10,000) and ~2.5% of your subjects' population.
The cost also increases by 5% for every 5 current court points up to 40, then by 10% for every 5 'til 70, then by 15% for every 5 after that.
That means that at 30 court points, the cost increases by 34%, at 60 court points it increases by 116% and at 90 points the cost increases by 357%.
But the effectiveness of your ducats (so how many court level points you get for one ducat) increases by 0.4% per year (sounds like a mistake, since the variable is called "costlier_with_time"...), and is multiplied by 2 as a tuning variable.
Overall, you need 1*cost/effectiveness ducats for every court point you want to have.
For a country with a population of 2,000,000, keeping an average court level of 4 in 1500 (so 55 court points) requires 2.75 * (10*1.96) / (1.55*2) = 17.4 ducats per year.
As a rule of thumb, I take the annual church payment for education at 50% church influence and triple that (if you want a good court). If you don't have any church influence left, just eyeball it and adjust as necessary. Then just remember your population and change it accordingly. Or just eyeball it all the time, and check in occasionally to see if your court level is dropping.