If you are new to the game, you might wonder what's the best way to be rich in STW2. The quick answer is to (1) occupy as many foreign trade nodes as possible, (2) fill the nodes with trade ships, and (3) sign as many trade agreements as possible.
But there are a few things we can optimize for the above general trading principles. How profitable are the individual trade nodes? How does trading compare to other means of money-making? This article answers the first question. And maybe in the future we can have a comprehensive analysis of tax income as well.
There are six foreign trade nodes. Newbies who played the Chosokabe tutorial might be looking for another node in Seto Inland Sea, but that trade node only exists in the tutorial. Four trade nodes are located in the west with relatively close proximity.
Quantity of Goods
Here comes a list of them and the quantity of goods they offer, each comma means one additional trade ship parked at the trade node.
Cotton: 12, 22, 32, 42, 52, 63, 73, 83, 93, 103
Silk: 12, 22, 32, 42, 52, 63, 73, 83, 93, 103
Incense (two nodes, identical): 8, 14, 21, 28, 35, 42, 48, 55, 62, 69
Warhorse: 5, 9, 13, 18, 22, 26, 30, 34, 38, 43 (reverse calculated from data under 25% bonus, could be off by +/- 1)
Iron: 5, 9, 13, 18, 22, 26, 30, 34, 38, 43 (same as above)
The kind of trade ship actually does NOT affect the quantity of goods received on the trade node. They are merely more powerful (and expensive) ships.
The number of goods received could be boosted by events. During Foreign Prosperity, there are 25% of extra goods. There is also a dilemma event that triggers the Foreign Prosperity, if we pay 2000 koku to Wako pirates at front.
The value of each goods varies. The following values are averaged by values collected over 10 seaseons. Again, the real in-game value could be slightly off.
Now we can calculate the maximal value of trade income we receive from trade nodes:
Cotton: 33 x 103 = 3399
Silk: 40 x 103 = 4120
Incense: 47 x 69 = 3243
Warhorse: 33 x 43 = 1426
Iron: 41 x 43 = 1763
Trade ships require upkeep, too. For example, on Legendary, each basic trade ship costs about 58 koku per season of upkeep. A full-stack cheapest trade fleet of 10 costs 580 koku per season. Of course, building the trade fleet also costs money. Each trade ship costs about 110 koku.
The profit from each trade node, when they are filled with trade ships, are therefore:
You can see that some trade nodes are a lot more profitable than the others. It is extremely unfair that the four most profitable trade nodes are all lined up in the west! The developers probably did it because the west has less fertile soil. But in reality they simply made the western clans a lot easier than the rest just because of the trade nodes.
The above case only presents the maximal profit in theory. In reality, we cannot sell all the goods to other clans. There is a limit of quantity of goods of each kind that a clan will buy from us, no matter how big they are. If we fill each trade node with a full-stack fleet, chances are we will saturate the export market, and the overflow goods have to be sold domesitcally. In that case, we earn half (or reportedly slightly less than half) of the full value of the goods.
We can also calculate the theoreticaly minimum trading profit - if we have absolutely NO trade partner.
Fortunately, the reduced profit still cover the cheap trade ship maintenance. So even for the poorest Warhorse trade node, we are still running a tiny profit.
Raids and Blockade
Sometimes, the sea trade route can be raided by a hostile fleet, which parks on top of a sea trade route. The value raided is positively correlated to the size of the fleet. Raiding happens quite rarely. The AI fleets usually try to blockade ports, and only if they are too weak to blockade a port would they resort to raiding. But since AI fleets never defend their port, their port is always suspectible to blockade.
When we establish a trade agreement with another clan, the game picks a province with a trading port (or above) which has the capacity of holding an extra trade route. This particular trading port is then our designated trading window with the clan. If this port is under blockade, all goods shipped to that port earns exactly 0 profit, like they are simply thrown into the water.
Unfortunately, port blockade happens very frequently, and it hurts because we still pay the trade ships' upkeep. It hurts a lot more than losing the trade to the clan all together, as in the latter case we can sell goods domestically for 1/2 price.
As a result, we should always avoid trading with a clan that has a tendency to have their port under blockade. These clans are the clans that usually has a very weak navy. Takeda is a prime example of 0 navy. Only trade with Takeda if we have a land-route connection with them.
We should also know a list of the clans that usually feature a powerful and aggressive navy that goes out to blockade their enemy's ports. And we should avoid sea trades with their enemies. Hojo, Ikko-Ikki, Oda, and Shoni are often seen with large fleets. So it is a good idea NOT to establish sea trade with their enemies who have a weak navy. By the way, I have never seen Honma's port on Sado island under blockade. So Honma is a good trade partner.
Signing Trade Agreement - a little tip
This is a well-known tip, just in case you do not know. In early-mid game, AI clans are often less willing to sign a Trade Agreement with us if we are going to profit a lot more than them from the trade. In this case, it is better to temporarily remove the trade fleets from the trade nodes, sign the trade agreement, then move the trade fleet back. However, after we become powerful and rich, the AI clans actually love to trade with us no matter how much more we are going to profit from the trade than they do.
Since trade ships can be built cheaply and quickly, once we secure a trade node, we can quickly fill it up with trade ships. If we fill the four western trade nodes, we already enjoy the profits that lies between 4815 (all domestic) and 11817 (all export) koku per turn. This income is disproportionally huge compared to conventional incomes sources such as tax in early-mid game. Only in late game does the tax income take over the trade income due to accumulated town growth.
Therefore, it might be a viable strategy for ANY clan to quickly build up a full stack of army and ship it to northern Kyushu to grab Hizen. Owning Hizen makes securing the four western trade nodes a lot easier, and the three very fertile provinces there also provide significant income themselves.
Typically in my current Oda campaign the only two free nodes were warhorses and iron....
However on these figures it makes sense to leave a trade ship by each occupied western node and a spare trade fleet nearby to pounce whenever a clan is destroyed or just abandons the node (which they randomly do for no apparent reason).