Trade is what an empire is built upon.
IntroductionLook after the pennies and the pounds will look after themselves.
Commerce becomes available in the Medieval Era and is focused on the economic side of the game. As a full tree it can benefit any Civilization when there are coastal areas and plenty of water, or indeed any situation in which you have high food/gold but low production tiles. It can give you extra movement for your ships, production for your cities, cheaper trade routes, increased gold for your capital and better luxury value. Upon inspection, Commerce is divided into two distinct strands: one focusing on the the naval aspects of the game, and the other on reducing costs and improving gold and luxury values.
Commerce in effect provides more options for your game, rather than forcing it down a particular path as other social policies are wont to do. A full Commerce tree will greatly increase your economic output which is, of course, essential to any game.
The alternative to taking the full tree of Commerce is to use particular social policies from it to benefit an existing strategy. Commerce has a few distinct policies which synergize very well with other social policy trees/wonders and map types. If pursuing this route with Commerce then you should not endeavour to fill the Commerce in its entirety as Liberty or Tradition tend to be.
Regardless of whether you go for a full or partial Commerce tree Commerce in general is something that augments a strategy, it is not (usually) one in and of itself. The benefit of Commerce is primarily a stronger economy which can be used in whatever way you desire.
OpenerAdopting Commerce will boost Gold output in Capital City by 25%.
Opening the commerce tree increases the Capital's gold output by 25%, stacking additively with markets and other percent modifiers. Any start with a high gold output capital position can see some very nice returns from opening Commerce, with one city challenge games gaining particular benefit. Anything that boosts the Capital's raw gold output such as building the colossus or national treasury increases the benefit of the opener. A tall empire, particularly one that has developed the Tradition tree, can really capitalize on this with relatively more gain than a wide empire. If running a very tall capital strategy, this policy is the only way to boost gold % modifiers over 100% (Opener+Market+Bank+Stock Exchange) which can make the free gold from Monarchy and the Commerce Finisher go much further.
Naval Tradition+1 Movement for Naval units and +1 Sight for Naval combat units.
Naval Tradition is the starting policy pick for the left hand side of the Commerce tree, and it is the only social policy in the game that directly enhances naval units (both ships and embarked units). An extra movement for all naval units and an extra sight for all naval combat units is quite nice. To put this in context, the bonus from Naval Tradition is about half of England's or Denmark's (DLC) Unique Ability, which have +2 Naval movement, and +1 Naval movement (and some other things) respectively.
Naval tradition is stronger than the Great Lighthouse, as its movement bonus affects embarked units as well as ships. Naval Tradition is easily the strongest policy for a navy of any Civilization. If you were to combine Naval Tradition with the Great Lighthouse your navy would receive +2 movement and +2 sight to all naval ships. For two policies (Opener+Naval Tradition) and a wonder you can nearly gain the equivalent of England's unique ability, with more +sight but less +movement for embarked units.
On that note, England, Denmark, Polynesia and the Ottomans will want to pick this to help increase their natural advantage on appropriate maps.
Merchant Navy+3 Production in all coastal Cities.
Requires: Naval Tradition
This is the biggest per-city production boost for a city from any social policy pick, although it is limited to coastal cities. Merchant Navy is one of the strongest policies in the entire Commerce tree on appropriate maps. An extra three production per city provided it is coastal, especially for a wide empire on a water map, can be quite a substantial boost.
Trade UnionsMaintenance paid on Roads and Railroads reduced by 33%. Harbors and Seaports gain +1 Gold.
Trade Unions is the first pick on the right hand side of the Commerce tree and is focused on the generation of gold. Trade Unions cuts road and railroad maintenance by a third, while harbors and seaports gain one gold. Again the focus on coastal cities is clear and the harbour/seaport boost alone represents a tidy bonus.
The road and railroad maintenance, however, can save a substantial amount of gold per turn. The reduction for the road is not that significant, but for even a basic railroad network connecting coastal cities can be quite powerful. A simple six hex railroad will have its maintenance reduced from 12 gpt to 8 gpt. The saving is small, but can mount up if the rail or road network is large enough. This makes it ideal for Pangaea or Continents maps, where Civilizations typically have relatively large road and rail networks. More information on the benefits of this can be found in the trade route guide.
Mixing Trade Unions with Meritocracy from Liberty can be a strong combination. This means that you can get the +1 happiness from Meritocracy with no net loss of gold with a two population city, so you can start trade routes earlier. This allows future expansion to occur earlier and every citizen above 2 in the new city will generate gold.
MercantilismPurchasing items in Cities requires 25% less Gold.
Requires: Trade Unions
This is one of the best, if not the best, social policy in the entire Commerce tree. This stacks additively with Big Ben's 15% reduction for a total of 40% reduction, and multiplicatively with Militarism's 33% unit price reduction for a near 50% reduction for units, or a 60% reduction on units with all three together. The utility of this Social Policy becomes more obvious the more you rush buy units or buildings. The benefits from Mercantilism tend to be reduced with the advent of factories, railroads and power plants as production is boosted, but the benefit can still be quite substantial especially if your gpt is higher in comparison to your production, a difference which is amplified by the reduced gold/hammer ratio in the late game. More detail on how to use this can be found in the general strategies section.
Tall empires may benefit slightly more than wide empires with this policy as it can free the limited number of production slots they have for things that cannot be bought, such as wonders. For a wide empire, this is of less relevance as with more cities they'll typically have more viable production cities. If you take Mercantilism, you should attempt to grab Big Ben as well to make the most out of the discounted rush buy costs.
Protectionism+1 Happiness from each Luxury resource.
The extra happiness from luxury resources would appear quite weak in comparison to other social policies that can be selected from other trees. Honour's Professional Army, Patronage's Cultural Diplomacy and Piety's Organized religion all do a better job of increasing happiness than Protectionism. However the main advantage of Protectionism is that it doesn't cost anything to maintain, unlike all of the aforementioned. Commerce's main goal of preserving gold is once again to the forefront of the policy.
The policy is dependent on existing luxury goods so a wide empire will, in most circumstances, benefit more than a tall one will although a strong city-state focus will often make up the difference between the two. At most Protectionism will give you an extra +15 happiness and this is only true if you are on a map of large size or greater as smaller maps will often not have all of the unique luxuries available. In practice (considering map size/diplomatic situation etc) it will probably yield something closer to +10.
One way to look at Protectionism is that it is Notre Dame as a social policy, but with a higher opportunity cost. To take Protectionism you need to invest four social policy picks (Opener - Trade Unions - Mercantilism - Protectionism) which may be too much to ask from a wide empire, although a tall one could take more benefit from it. You also need to bear in mind that Honour (Professional Army), Piety (Organized religion) and possibly even Patronage (need to pay less for the same luxuries from city states) will result in more happiness for a wide empire at less social policy cost.
That said, a wide empire with a significant road or rail network and a strong gold producing capital can benefit reasonably substantially from this line of social policies. Much more so than a tall empire would, which typically do not have a large enough road or rail network to gain much from Trade Unions.
FinisherAdopting all Policies in the Commerce tree will grant +1 Gold from every Specialist.
Commerce finishes on what would appear to be a dull note. However, an extra gold from every specialist is a nice addition, especially for coastal cities which can typically be running a few engineer specialists to make up for their lack of production. By the time you have this, however, you will have already unlocked Mercantilism with its discount for rush purchasing and so purchasing might be better than building, which can potentially make engineers redundant.
The strength of the Commerce finisher lies in the merchant specialists, which now provide +3 gold a turn. This will usually be greater than unimproved sea tiles and will make them better at producing gold than even river based trading posts until Economics, at which point they become equal and the question becomes whether the extra great merchant points are worth the loss in food.
You're a kid in a candy store.
In general, Commerce is not a tree in which it is optimal to pursue every single choice. It certainly isn't one that you should select if you're going for a Cultural victory (exception outlined below). As a whole tree Commerce is weaker than its counterparts, and is arguably one of the weakest trees in the whole game. The problem with Commerce is that Naval Tradition is too dependent on a particular strategy as is Trade Unions and these strategies tend to be mutually divergent. Naval Tradition typically suits water heavy maps best while Trade Unions best suits land heavy maps. Protectionism is weak for its position in the tree and gets poorer the smaller the map you play on. The finisher, meanwhile, is mediocre except when attempting a specialist economy. In spite of this, or perhaps because of it, Commerce does have two very strong policies; Mercantilism and Merchant Navy. These are easily the two best policies in Commerce regardless of the situation and could quite possibly be amongst the strongest of any single policy pick.
The extra +3 production from Merchant Navy does require the weaker Naval Tradition, but it can add some much needed production to your coastal cities. The 25% discount from Mercantilism is good regardless of map and if social policies aren't part of your victory conditions, then taking Trade Unions and then Mercantilism can save quite a bit of gold for you. Combining Mercantilism with Big Ben gives you a total of 40% off of any purchases, which can make buying units and buildings ridiculously cheap.
The point of Commerce, however, is that it provides you with options for your gold, or to capitalize on a water-heavy map. With this in mind, attempting to fill the tree is not necessarily the best use of your culture and so you should cherry-pick from the Commerce tree rather than fill it. Generally speaking, this means dipping in to it for Mercantilism and/or Merchant Navy.
The Commerce sweet spot: Small continents
Is that a leprechaun? ... It is!
However, there are some situations in which the entire Commerce tree can be very useful and should be filled. This is ideally on a medium sized continent on a standard sized map upon which you are isolated (or are perhaps joined by a city state or two). This is most easily come across in the small continents map type, but is known to happen on continents as well.
The reason for this is that an isolated small continent start on a standard map can potentially yield 5-7 coastal cities with few hexes wasted due to overlap or lack of reach. All of your cities being coastal is important to get the most out of Merchant Navy. A lot of water is required for the most advantage to come from Naval Tradition. A reasonably sized road/rail network is the best compromise between the right and left sides of the tree. Mercantilism will work regardless as will the extra from luxury resources while your isolated start allows you take Tradition (to maximise the potential from a specialist economy) and keep social policy costs down. Once the key social policies have been taken, there will be much more freedom to expand.
Maximising Commerce: Rushbuying vs. Production
To buy or to produce? That is the question.
As the entire tree (with notable exception to Naval Tradition) is related to boosting your net economic gain either by reducing costs, increasing gold production or increasing production output, a brief word on the shift from production to gold in terms of the most cost efficient way of producing items is warranted.
The rush buying formula features the production cost of units taken to an exponent less than one, which results in more expensive hammer cost items costing relatively less gold. Take two units: a Warrior and a Nuclear Missile. On standard speed the warrior costs 200 gold or 40 production and the nuclear missile costs 2270 gold or 1000 production. If you calculate the gold per production, the warrior is more expensive to buy (5 gold/production) making it more efficient to build than buy. The nuclear missile, however, is relatively cheaper (2.27 gold/production) and so is more efficient to purchase. The conclusion to be drawn, therefore, is that it is more efficient to purchase items in later eras than it is in earlier ones.
The advantage in purchasing these units is, however, greater when Mercantilism (-25% cost of purchase) and Big Ben (an additional -15% cost of purchase) are factored in. The nuclear missile costs 60% of base, from 2270 gold to 1360 gold with both Mercantilism and Big Ben. Its production cost remains static at 1000. This means that rushing buying a nuclear missile costs only 1.36 gold per hammer, the best gold to hammer ratio purchase in the game.
Note: The particulars of rush-buying units and buildings are covered in more depth here, including the penalty costs for rush-buying units and buildings in the pre-Renaissance eras.
I am just a cog in a machine.
Commerce is one of the key social policies in creating a specialist economy because of its finisher, which boosts gold from specialists by 1. The other three are Tradition, Rationalism and Freedom.
It will take, approximately, 17 social policies to max out the benefit of a specialist economy from social policies. This is partly why a specialist economy has particularly good synergy with the semi-wide/semi-tall result that an isolated small continents start can achieve. Ensuring the cost of your social policies is kept low will require very limited expansion initially until the social policies are completed, at which point moving wide makes more sense. This means that the quickest way to a specialist economy is a tall (possibly even one city) start until after the Commerce tree is finished, and at that stage start planning where you'll settle once the remaining policies come online.
- Tradition is needed to provide for the extra food bonus, which is needed to help support specialists. In particular, Landed Elite and the Finisher are important here.
- Commerce is needed to provide for the extra gold per specialist from the finisher, while nabbing Mercantilism and Merchant Navy along the way is a major boon.
- Rationalism is only needed for Secularism, although the fact that the opener increases RA's by 50% is a plus.
- Freedom is, of course, of critical importance to any specialist economy, although only Civil Society and Democracy are needed to reduce the unhappiness and food penalty.
On the point of maxing out specialists, the Statue of Liberty is critical. It isn't so critical that if another gets it the entire economy is ruined, but critical enough that bee-lining for it is important.
An unemployed citizen at the end of the 15 policies with the Statue of Liberty will be equivalent to working a tile with +1 , +2 , +2, +1 , +0.5 and this is before he is specialized, say as an engineer or scientist.
The Commerce tree finisher unlocks the first boost to specialists, but the tipping point for switching to a specialist economy does not really start until after the adoption of Secularism. With the Commerce finished and Secularism alone, an unemployed citizen consumes 2 and 1 to produce +1 , +2 , +1 , which is good but not great. The extra production from the Statue of Liberty, and the reduction in food and happiness cost from the Freedom line are what pushes the specialist economy to a possible goal with which Commerce can work well.
Nobody expects a bibliography.
Patch version of this article: 126.96.36.1993
Social Policy: Commerce (vanilla)
Social Policy: Commerce