This article is a joint contribution to this community by colony and Roland Johansen. We had some trouble getting the formulas in this article exactly right, but after correcting each other a few times, the correct formulas are now known. The article provides information for Civilization 4 versions 1.09 and 1.52 but mainly for version 1.52.
The article is divided in a few sections. The first section is a general introduction in the civic upkeep cost and probably contains no new information for most civilization 4 players. The second section explains how the game determines these costs. If you don’t like mathematics and mathematical formulas, then you might want to skip this section and go on to the third section. The third section is about some strategic consequences of the way civilization 4 determines the civic upkeep cost. The fourth section gives some information to modders. It talks about the files where they can change the civic upkeep cost and about the consequences of adding more categories of civics. The last section mentions a utility created by Qitai that can calculate the civic upkeep cost.
The civic upkeep cost can be found in the financial advisor (F2) and in the change civics menu (F3), but the financial advisor is more useful to get a clear overview of the costs. If you mouse over the civic upkeep section of the financial advisor (F2), then the civic upkeep cost is broken down into the five well known sections: government, legal, labor, economy and religion. The upkeep cost of a civic is largely determined by its upkeep classification: no upkeep, low, medium or high. A low upkeep labor civic will cost about the same amount in upkeep as a low upkeep economy civic and a high upkeep government civic will cost about the same as a high upkeep religion civic. The change civics menu (F3) allows you to see the upkeep cost of another set of civics when you mouse over or select these civics. You can always cancel the revolution, so there’s no risk in doing so.
When a set of civics is chosen, then the upkeep cost is largely determined by the size of your empire: the number of cities in your empire (M) and the total size of your population (N). Also the organized trait (O) and the difficulty level (D) will have a large effect on the final upkeep cost. How the game determines the civic upkeep cost from these variables, can be found in the next section.
How the game calculates the civic upkeep cost
The civic upkeep cost is dependent on some factors in the game. To make the description of the civic upkeep cost short and hopefully clear, a set of variables is introduced below.
The upkeep of a civic is largely determined by its upkeep classification in the game (no upkeep, low, medium or high) in combination with the size of your empire. We denote the number of cities in your empire by M and the total size of your population by N (the sum of the population from all of your cities). The population modifier P determines the civic upkeep of running a civic of a certain upkeep classification in an empire of a certain population size (N). In civilization 4 version 1.09, the variable P is equal to 0 for civics with no upkeep cost, 0.05 for civics with low upkeep cost, 0.10 for civics with medium upkeep cost and 0.15 for civics with high upkeep cost. In civilization 4 version 1.52, the variable P is equal to 0 for civics with no upkeep cost, 0.08 for civics with low upkeep cost, 0.12 for civics with medium upkeep cost and 0.16 for civics with high upkeep cost.
Likewise the number-of-cities modifier C dictates the civic upkeep cost of running a civic of a certain upkeep classification in an empire consisting of a certain number of cities (M). In civilization 4 version 1.09, the variable C is equal to 0 for civics with no upkeep cost, 0.2 for civics with low upkeep cost, 0.4 for civics with medium upkeep cost and 0.6 for civics with high upkeep cost. In civilization 4 version 1.52, the variable C is equal to 0 for civics with no upkeep cost, 0.4 for civics with low upkeep cost, 0.5 for civics with medium upkeep cost and 0.6 for civics with high upkeep cost.
Last but not least are the effect of the organized trait, denoted by O and the effect of the difficulty level, denoted by D. The variable O is 1/2 if your civilization is organized and 1 if your civilization is not organized. The difficulty level modifier for the human player is 1 at deity, immortal or emperor level, 0.95 at monarch level, 0.9 at prince level, 0.8 at noble level, 0.7 at warlord level, 0.6 at chieftain level and finally 0.5 at settler level.
The difficulty level modifier for the AI is 0.6 at deity level, 0.8 at immortal level, 0.85 at emperor level, 0.9 at monarch level, 0.95 at prince level and 1 at the levels below prince.
It’s a bit strange, but the civic upkeep cost is also dependent on the type of civic. A medium cost economy civic is close in upkeep to a medium cost government civic but not exactly the same. I think this was done to avoid the situation where one of your cities grows one unit in population or you build one additional city and suddenly all of your civics will rise in upkeep cost. Because of the small differences in the formulas, this will seldom happen. Take a look at the formulas below and you’ll see that there are some minor differences:
Government civics upkeep:
[D * [ O * ( [ P * (N-8) ] + [ C * (M-1) ] ) ] ]
Legal civics upkeep:
[D * [ O * ( [ P * (N-9) ] + [ C * M ] ) ] ]
Labor civics upkeep:
[D * [ O * ( [ P * (N-10) ] + [ C * (M+1) ] ) ] ]
Economy civics upkeep:
[D * [ O * ( [ P * (N-11) ] + [ C * (M+2) ] ) ] ]
Religion civics upkeep:
[D * [ O * ( [ P * (N-12) ] + [ C * (M+3) ] ) ] ]
Terms between brackets [….] are to be rounded down. So there is a lot of rounding down in these formulas. Note that there is a clear pattern in these formulas, but to keep the format of the formulas somewhat readable, the formulas were presented independently and not in one big formula.
Of course, the total upkeep cost for civics is determined by adding the costs of all of the chosen civics.
An example (for civilization 4 version 1.52):
You are playing a game at Noble difficulty level and own 11 cities of sizes: 9, 7, 12, 8, 15, 14, 12, 11, 11, 15 and 14. So your total population is 128. You’re running the civics representation, bureaucracy, serfdom, decentralization and organized religion. Your leader has the organized trait.
Then according to the formulas, the upkeep cost for representation (low upkeep) is:
[0.8 * [ 0.5 * ( [ 0.08 * (128-8) ] + [0.4 * (11-1) ] ) ] ] = [0.8 * [ 0.5 * (9 + 4) ] ] = [0.8 * 6] = 4.
The upkeep cost for bureaucracy (medium upkeep) is:
[0.8 * [ 0.5 * ( [ 0.12 * (128-9) ] + [0.5 * 11 ] ) ] ] = [0.8 * [ 0.5 * (14 + 5) ] ] = [0.8 * 9] = 7.
The upkeep cost for serfdom (low upkeep) is:
[0.8 * [ 0.5 * ( [ 0.08 * (128-10) ] + [0.4 * (11 +1) ] ) ] ] = [0.8 * [ 0.5 * (9 + 4) ] ] = [0.8 * 6] = 4.
The upkeep cost for decentralization (low upkeep) is:
[0.8 * [ 0.5 * ( [ 0.08 * (128-11) ] + [0.4 * (11 +2) ] ) ] ] = [0.8 * [ 0.5 * (9 + 5) ] ] = [0.8 * 7] = 5.
The upkeep cost for organized religion (high upkeep) is:
[0.8 * [ 0.5 * ( [ 0.16 * (128-12) ] + [0.6 * (11 +3) ] ) ] ] = [0.8 * [ 0.5 * (18 + 8) ] ] = [0.8 * 13] = 10.
And thus the total civic upkeep is: 4+7+4+5+10=30.
Some repercussions of the way the game calculates the civic upkeep (for civilization 4 version 1.52)
The above formulas are all nice and such, but nobody is really going to use them when playing a game of civilization 4. But they can offer a deeper insight into the workings of the game. This might help you play the game a little better or help create a nice balanced mod for the game.
- The no upkeep classification is a pretty big advantage for a civic. The difference in upkeep between no upkeep and low upkeep is larger than the difference between low upkeep and high upkeep. Especially in empires with lots of large cities, the no upkeep classification is very powerful.
- In empires with small cities, the differences in upkeep classification don’t mean very much (with exception of the above noted no upkeep classification). In empires with large cities, the high upkeep civics cost almost twice as much as the low upkeep civics. The medium upkeep civics have a cost halfway the low and high upkeep civics.
- Because the civic upkeep is higher at the higher difficulty levels, the organized trait is a more interesting trait at these higher difficulty levels. You can already notice this right from the start of the game. Normally at the highest difficulty levels, you can not set your research slider at 100%. But if you start with the organized trait, you can research at 100% getting those first few technologies a bit sooner. Later in the game, you will probably also be able to set the research slider at a higher rate thanks to the reduced cost of civic upkeep.
- Civic upkeep limits fast expansion. When you start developing your empire, then your cities tend to be small and don’t make a lot of money. Still a lot of small cities tend to cost a considerable amount in civic upkeep. When the cities grow, the civic upkeep also grows, but not as fast as the commerce production of well developed cities. A city of size 10 will produce far more commerce than a city of size 1 (say 5-20 times as much, depending on how well it is developed), but it will cost less than 3 times as much in civic upkeep. Clearly large cities can cope with civic upkeep cost better than small cities.
- The organized trait has an effect that tends to be a bit larger than halving the civic upkeep, especially at the beginning of the game when the civic upkeep is still low (the reason is the rounding down in the formulas). This can make this trait very interesting for warmongers who tend to get lots of small cities early in the game. The low commerce production of these cities combined with a high upkeep, high civic upkeep and high unit upkeep can spell disaster for warmongers who are a bit too successful in their wars.
- The civic upkeep for human players is lower than the civic upkeep for AI’s at the levels settler, chieftain, warlord, noble and prince. So while the AI has some advantages at noble level, it also has some disadvantages.
- Inflation is a percentage that adds to all types of costs and rises uncontrollably throughout the game. Because inflation can rise as high as 100%, the costs of civics can be doubled in the late game. This might make you rethink using those expensive civics.
- Free unit support also grows with population size. So while the cost of maintaining your civics grows when your cities grow, the free support for your units also grows. This means that a growing empire’s expenditures don’t necessarily increase that fast. If your leader is organized and you’re running low cost civics, then the effect of the increase in free unit support could even be greater then the effect of the increase in civic upkeep.
- A rule of thumb for the costs of running the lowest cost civics, the highest cost civics and an average cost example. This can be useful to estimate the profitability of a city in the long run before you even found it. You can estimate the amount of cottages needed to make a single city a profitable entity. Of course, not every city has to pay for itself.
If you use the civics in the game with the lowest possible cost (2 low cost civics and 3 no cost civics), then the civic upkeep cost will be 0.16 gold for each point of population and 0.8 gold for each city.
If you use the civics in the game with the highest cost (3 high cost civics and 2 medium cost civics), then the civic upkeep cost will be 0.72 gold for each point of population and 2.8 gold for each city.
If you use my favorite civics (universal suffrage, free speech, emancipation, state property and organized religion) which have an average cost, then the civic upkeep cost will be 0.44 gold for each point of population and 1.9 gold for each city.
Note that these costs are reduced at the lower difficulty levels and are halved by the organized trait. Also note that the inflation percentage can increase the costs considerably and almost double these costs in the late game.
Some information for modders
I guess most people who mod civ4 will find the files by themselves. Still, these files were useful to find some numbers and might as well be mentioned. The modifiers for difficulty level are of course in the file CIV4HandicapInfo.xml named iCivicUpkeepPercent for human players and iAICivicUpkeepPercent for AI’s. In the file CIV4UpKeepInfo.xml, the numbers can be found that determine the effects of low, medium and high upkeep costs. In the file CIV4CivicInfos.xml, the upkeep classifications (no upkeep, low, medium, high), can be set for each civic. Also every other effect of civics can be changed in that file.
If more categories of civics are added, then it can be expected that the formulas that determine civic upkeep costs will follow the same pattern. So a sixth category of civics will probably have the following upkeep costs:
[D * [ O * ( [ P * (N-13) ] + [ C * (M+4) ] ) ] ]
Utility for calculating civic upkeep costs
Qitai has created an excel spreadsheet which can calculate the civic upkeep cost for you. It can be used to see how civic upkeep cost will develop while you expand your empire. Thanks Qitai!