Introduction
There are eigth leader traits in the game, all with very concrete and tangible benefits. However, some of them give more and some of them give less benefit than what they look to be giving on the surface. Im going to explain how much benefit each actually gives. This article will take the mathematical approach, as Im measuring the magnitude of the traits bonuses, rather than subjectively comparing them.
Generally for all traits
Most of the traits have one or more city improvements associated with it that it gains double production speed of. However that doesnt always mean the improvement is procued twice as fast, because the 100% bonus to hammers is of the base production. So if you already have a forge, building an improvement associated with your trait will make the total production speed rise from 125% to 225%, rather than 250%.
Lets say, for example, that you have the spititual trait, which gives half price on temples (80 hammers). With no other production enhancing improvements the spiritual trait will account for half of the hammers needed (40 hammers). However, if you have a forge the spiritual trait will only account for 100 / 225 = 44,4% of the hammers needed (35 hammers). As more production enhancers are added (e.g. organised religion, factory) the percentage of the hammers that the trait bonus contributes becomes increasingly smaller. While this may seem minor and insignificant, in the big picture it can total up to a significant amount of hammers.
The Traits
Aggressive
Free Combat I promotion of melee and gunpowder units.
To a melee or gunpowder unit with no experience this trait is worth exactly what it says: a Combat I promotion giving 10% increased strength and equal to what the unit could achieve with 2 xp. As the unit levels up however, this combat I promotion rises in value. Lets say you have a unit with 17 xp giving it four promotions, and you want it to eventually have the commando promotion. With the Combat I promotion from the Aggressive trait you would be able to take commando promotion now (Combat II - IV and then commando), but without it you would only be able to promote your unit up to Combat IV. For the non-aggressive civ the experience required to get the commando promotion and have a unit as good as the aggressive civs, is 26 which is 9 additional xp. In this case the Aggressive trait is worth 9 xp. In other words, the actual value of the aggressive trait is the amount of xp required to get the next promotion for a unit, providing you are upgrading in the Combat part of the promotion tree or that the Combat I promotion is useful to the unit. This means that the value of the trait increases with more experienced units because the xp required for a promotion is n^2 + 1. To put it more simple, if you are upgrading along the Combat part of the tree, the latest promotion you have chosen is your actual tangible benefit of having the aggressive trait.
Creative
+2 culture per city.
This trait is pretty straightforward magnitude-wise. It will always add 2 culture to the citys base culture. This can be multiplied by cathedrals and a few wonders, but it should be noted that since the rest of the citys culture production will also increase proportionally, the percentage of the citys total culture that this trait is accountable for wont change with the culture multiplicative improvements.
Expansive
+3 health per city.
This trait is also straightforward. The bonus is always 3 health for all cities and is never subject to multiplications or the like. The tangible benefit is between 0 and 3 food depending on how your health situation looks before and after the traits bonus is applied. It can also make the difference between whether a city is eligible for We Love the King Day or not, saving an average amount of upkeep per turn depending on what the citys upkeep cost is.
Financial
+1 commerce on plots with 2 commerce.
Financial is a trait that requires more calculation. It adds to the cities base commerce and is therefore subject to modifiers. Improvements or civics that multiply the science, gold or culture output of the city will all increase the benefit of the financial trait providing you are allocating at least 10% of your base commerce to the category in question (science, gold or culture). Improvements or civics that multiply the base commerce (e.g. Bureaucracy) increase the benefit regardless of slider settings. In short, the benefit of the financial trait in absolute numbers is the base commerce it adds (number of tiles worked that produces at least 2 commerce) multiplied by any modifiers present in the city.
Calculating its effect in relative numbers is relevant too though. In this case the multiplicative improvements and civics makes no difference as they are applied to all base commerce, not the just the commerce from the financial trait. What matters is a comparison between commerce before and after the trait is applied. The largest increase financial can result in is 50%, if all tiles produce exactly 2 commerce before its applied. If a tile produces, for instance, 5 commerce, the advantage of adding the financial trait will be 20%. As a tiles commerce increases further the relative benefit decreases. Of course tiles can also produce less than 2 commerce in which case the benefit is 0%. In short, the relative benefit of the financial trait always lies somewhere between 0% and 50%, depending on how much commerce is being produced in the individual tiles.
Industrious
Wonder production increased 50 percent.
The calculations about the actual benefits of the trait-specific building bonuses also apply to the industrious trait, as the wonder production bonus is applied in the exact same way. There really isnt more to say about that as its already explained in that chapter.
Organised
Civic upkeep reduced 50 percent.
The benefit of the organised trait seems to be straightforward as it simply halves your civic upkeep expenses. However, the amount of gold that this trait saves you cannot be calculated just by looking at the remaining half that you are paying, because inflation factors in. By multiplying the upkeep that you appear to be saving with (1 + inflationrate) you will know how much gold this trait is actually saving you.
Another aspect of the organised trait to consider is the difficulty level. At lower levels the civic upkeep is relatively low and increases with difficulty level. As such the organised trait generally saves you more gold on the higher levels. The inflation rate is also higher on the harder difficulties, further increasing the benefit of organised on these difficulties.
Philosophical
Great People birth rate increased 100 percent.
This is perhaps the most discussed trait regarding the actual benefit. There are countless threads on this, but Ill go through the non-subjective facts anyway.
The philosophical traits bonus works just like the trait-specific building bonuses and is subject to the same calculations regarding how much of the total output that it contributes. As with the industrious trait I wont go into detail about this as its explained in the first chapter. The only difference is that the possible production enhancers are the Parthenon, the National Epic and the pacifism civic.
Other production enhancers aside, the philosophical trait produces 100% more GPP (Great People Points), but that doesnt mean it produces 100% more GP (Great People) during the course of a game. This is because the cost of getting the next GP increases each time you get one and as such, getting a certain amount of extra GPP is worth less the more GP you have already produced. Through calculations which I wont bother you with it appears that the philosophical trait results in 50% more GP during the course of a game, all other things being equal.
If you look at the amount of turns it will take to produce a certain amount of GP however, the philosophical trait accomplishes it twice as quickly. This is because we are talking about a predefined amount GPP, in which case the 100% extra production results in achieving the GPs twice as quickly.
Spiritual
No anarchy.
The spiritual trait appears to be a relatively easy trait to calculate the benefits of. It simply saves you the amount of hammers, food etc. that would have been wasted during the anarchy turn(s). It isnt as simple as that, however, as cities will have to spend the turn after the anarchy to produce what they would have done during the anarchy and as such they are essentially wasting their latest turn. To put it simpler, your cities development are delayed by the amount of turns the anarchy lasts and because of that the penalty of the anarchy period is actually the latest turn(s) in the game. It isnt your whole empires development thats being delayed though, as units can still move, you still receive gpt payments from other civs etc. during anarchy. In short, the spiritual trait is worth more than just the amount of hammers, food etc. wasted on the anarchy turn(s) itself. It is rather worth what you would be producing at the end of the game.
-Theoden
