europa-universalis-iv
I've read up on the trading topics both here and on eu4wiki, but I'm still a bit puzzled.
Should I only send trade ships to nodes in which one of my merchants is present? Would adding light ships to a downstream node without my merchant improve my steering factor in any way, or would that be wasted?
Trade steering is used for two primary purposes. To move trade from areas where you have low power to areas where you are dominant, and to move trade from a node to the node where your capital is to avoid taking a trade power penalty. Trade being pushed downstream occurs wihtout a merchant in nodes other than your capital, but you cannot change which direction trade flows downstream unless you have a merchant there.
Here is an example of a game where trade steering is useful:
In this game I have roughly 50 percent power in both the Tunis and the Sevilla nodes, but my capital is in Sevilla. Because of this, the best course is to move trade downstream from Tunis, which sends 2.5 gold out of 5 to the Sevilla trade node. In Sevilla, I can capture 50 percent of that trade and get a total of 1.25 gold from the tunis node, times my actual income modifiers. On the other hand, if I tried to collect trade in tunis, i would take a 55 percent penalty to trade power, leaving me with only around 25 percent power. That would let me collect only .66 gold times Actual income. Trade steering is twice as good here. If I had no merchant at all, my power would push trade downstream, but aragon would make that travel to genoa instead of Seville. I would lose out on ALL income.
This is what the trade map looks like with no merchant:
I get absolutely nothing from the Tunis trade node, because I have no merchant there. This is caused by Aragon steering trade toward Genoa.
While it is possible to steer trade upstream, it is virtually useless to use a merchant to do so because the trade power penalty is severe. Steer trade downstream, not upstream.
Instead, you should relocate your capital to a the node that is furthest downstream which you dominate, and then direct trade there.
Should you always steer trade to your capital? NO!
Usually you will want to direct trade downstream, but not always. You don't direct trade through nodes where other players/AI have a lot more trade power than you, especially your enemies.
One good example of a situation where directing trade would be a bad idea occurred in my most recent game as Netherlands. I had a large number of colonies in the Chesapeake bay node. However, if I directed trade downstream, it would have been collected by England or Norway, in The North Sea and London nodes between Chesapeake Bay and Antwerpen. Instead, it was better to just collect trade.
Many people will tell you that you should extract trade only at your capital. This is FALSE. Here is an example of how much you can pull out of a non-capital trade node, without investing any ideas in trade. This is more than even in my capital.
The key to note is that I control 93.5 percent trade power, even with the large penalty to trade from collecting without a capital present:
This is because the trade penalty for collecting from a non-capital node is a trade power penalty, which means if you still have a higher percent power in a non-capital node than in your capital after the penalty, you should definitely collect there
Not a direct penalty but it does lose you money you shouldn't be losing.
Warships should not be unmothballed unless you're about to go to war or feel you're at risk of being declared on.
They add nothing to a trade fleet at all but by having them unmoth-balled you're paying half their upkeep for nothing which especially where heavies are concerned can completely overwhelm what you get from protecting trade.
And during war-time your whole fleet should be together until you've destroyed all the enemy ships and even then, blockading usually brings in more money then protecting trade does until you no longer need the light ships to help blockcade and can send them back to protecting trade.
And the speed of a light-speed is largely meaningless, as once the fleet reaches the trade node it's always considered protecting trade there until you tell it to do something else, no matter where it actually is (if you're at the edge or beyond your supply range your ship will occassionally need to head to port to repair, which doesn't affect your trade income since it's still considered protecting the node. But if you manually tell the ship to do something else, it needs to return to the node before the protect trade bonus kicks back in.
Speed matters more for exploration. And only because of the attrition, they can go farther and make it back more reliably if the fleet is only light ships. Or in the case of El Dorado where you don't give a crap about attrition while on the explore mission, it at least helps you explore a little faster.
Fleets move at the speed of the slowest ship, so mixed fleets also don't matter.
Best Answer
Basically, you would attempt to steer trade power (TP) back to the node in which you have your capital, as that is where you will potentially collect the most. You would use your light ships to add trade power to the nodes, so as much as possible gets steered in the desired direction.
However, in practice it is not so simple. It is possible to have high TP in a node, with no merchant, and still benefit from it. Let's break it down.
Trade power can be used to either steer trade value, or to collect. If you have no merchant present, the default mode is to steer trade away from the node (exception: you always collect in the node in which you have your capital).
Thus, as you add more ships, more value will leave the node. However, since you have no merchant present, you have no power over where that trade is going.
If no nation has a merchant present, the trade will be evenly divided between all outgoing routes. If any nation decides to add a merchant to influence the direction of the trade, all outgoing trade is going in the direction they choose. If the trade is already going where you want, you can add more ships to ensure more value is transported your way. No merchant needed!
Practical example from my own game (with made-up numbers)
I am Norway, my home node is North Sea, and I automatically collect there. I have two merchants. I also control the coast of Eastern America through a subject nation (Vinland).
First node
The Caribbean has 20 ducats in trade value and two outgoing routes. Cuba has high trade power, and collects 100% of the trade value. I transfer ships to match their trade power. Now 50% (10 ducats) is going out of Cuba, even if I have no merchant present.
Vinland prefers that trade to go to Chesapeake, where they are collecting, so they send a merchant to pull trade in that direction. 100% of those 10 ducats are thus transported forward to Chesapeake, even if they add no ships of their own – my massive trade power is making sure value is being transported out, they only influence the direction.
Second node
I don't want the trade to stay in Chesapeake, however, so I add ships (trade power) to that node, so the value will be going out once more. Portugal wants the same, so they also add trade power. Our combined trade power matches Vinland 9:1, thus 9 ducats will leave Chesapeake, and Vinland will only collect 1 ducats out of the incoming 10.
However, the Portuguese add a merchant to steer all that trade to Western Europe. No bueno! I also add a merchant, to steer the trade further to Gulf of St. Lawrence. Let's say I have double their trade power, so out of the 9 ducats, 6 will be transported to Gulf of St. Lawrence, while only 3 make it to Western Europe.
Third node
In Gulf of St. Lawrence, pretty much everyone agrees the trade can not stay there. Even if some Indian native nations try to collect, Portugal and I both add all our remaining ships, so no trade is staying in the node.
There are two outgoing routes, so 3 ducats are going to the North Sea, and 3 to Western Europe. However, as I add my second merchant, I can steer that trade in the direction I want, and since Portugal have no merchant to influence the direction of the trade, everything is going to the North Sea, where I collect everything.
Haha, stupid Portuguese
If Portugal wants in on the cake, they need to add a merchant. Right now, I am the only one of us benefiting from their light ships, thus if they have no merchant to send, they will probably send their ships somewhere else.
Oh, cool, so this will always work, right?
In my actual game, I managed to transfer 17 ducats from the Carribean to the North Sea. Pretty good, especially considering I owned almost every province in the North Sea trade node and thus could collect nearly all of it. However, all the other European jerks decided Norway doesn't need money, so they added a whole lot of light ships, to make sure the trade value would leave the node again, so all my efforts was for no gain. It actually made more sense to collect the value in North America.
However, some nodes, like Venice have no outgoing routes – 100% of the incoming trade is collected! If you dominate that trade node, and manage to steer a lot of trade into it, there is no way to transfer value out (well, a minimal amount can be transported upsteam, but it's insignificant).
In conclusion
To answer your question: No. Sending light ships to a node in which you have no merchant is not wasted. Adding light ships will make sure more trade leave that node. This is beneficient, if you know where that trade is actually going. In my first example above, Vinland was pulling trade in my desired direction, but had very little trade power. When I added my merchant fleet, it had a huge effect. I didn't have to add a merchant to transfer trade power – that is done automatically when I add my ships, Vinland only affects the direction.
Also remember, that you can use this power for evil. If one of your enemies is relying on trade, you can basically shut down their income by making sure all trade is leaving the node they are trying to collect. If you add a lot of ships, the trade will leave the node, and they will earn less money. If you care about where the money is going, you may need a merchant to steer the trade.