Prologue

Note: The screenshots use version 1.15 of the game.

0 Tooltips

In general, never blindly trust the tooltips and their numbers.  The descriptions are often more frustrating and confusing than informative.  However, I actually will use screenshots of tooltips where they actually are helpful or where I have been able to decipher them.  I will highlight those tooltips in screenshots as the key to playing this game (or any computer activity that shows you a bunch of numbers on the screen) is to stare at the numbers that are actually useful to the human, since often the screen in EU4 is just an onslaught of numbers that sometimes make sense and sometimes don’t.  Gradually, though, I will attempt to explain all the numbers on the tooltips that appear in the trade node screens and map mode.

I.a Trade Value Produced by a Province

Figure I.a.1: Town A produces salt.  That is town A’s trade value.  Boats take the salt from town A and move them to a market in town B.  Other boats then move them to town C, etc.  Who has control or jurisdiction over the activities of those boats (e.g. through taxing or regulating the merchants who operate the boats)?  Who controls the laws and taxes in these market towns of B and C?  That’s trade power.  Trade value is produced by a town.  Trade power is controlled by the ruler of the country.

Screenshot I.a.1: Granada produces salt.  (Every province produces one and only one type of good.)  The game tells us that 1 unit of salt is worth 3.00 ducats (the bottom-right of the province info screen, under the picture of a pile of salt).  In the bottom-left, it says that the trade value of Granada’s production is 3.60.  Hover your mouse over that, and the tool tip tells us that this comes from 3.60 = 3.00 (value of 1 unit of salt) × 1.20 (units produced by the province).  Where does this 1.20 come from?

Screenshot I.a.2: Granada’s base production.  Hover over where I’ve put a red rectangle and circle on that “6,” and the tooltip tells us that Granada has a base production of 6 and that each unit of base production gives 0.20 units of local production.  This is how Granada produces 1.20 units of goods.  But it doesn’t tell us if this is a monthly or yearly amount…

Screenshot I.a.4: In the Economy tab, the red box I highlighted shows the country’s total Production Income from all the country’s provinces.

Summary: A province’s trade value is measured in ducats and comes from the value of the trade good it produces multiplied by its production amount (which comes from its base production, which Granada has 6).  Modify by modifiers such as technology, production buildings (workshops), etc. and you arrive at the province’s production income.  The country earns this as revenue from this province every month (the 0.37 from above).

While a province produces *trade value* via [trade good × base production] (× modifiers) as we have seen above, a province produces *trade power* by [province development + geographical bonuses + buildings + …] (× modifiers) where we’ll just call the first part flat bonuses, i.e. a province’s trade power = [flat bonuses] (× modifiers).

Screenshot I.b.1: Trade power of the province of Sevilla.  Hover over the “Trade Power 120.4” in the bottom-left.  A province’s trade power comes from its flat bonuses to trade power, and then adjusted by modifiers.

Flat bonuses in Sevilla:

4.60 from “Development” comes from its total provincial development of 23 (boxed in red in the screenshot) and then divided by 5 (apparently, the game just assumes you like doing this kind of mental arithmetic);

10.00 from having an “estuary” comes from Sevilla’s geographical position – some provinces, like Sevilla here, are hardcoded by the game to have a boost in trade power;

another 10.00 from being a “coastal center of trade” is also hardcoded by the game for Sevilla here;

and 20.00 from Port to the New World is from an event (an exception here, so don’t worry about it).

Modifiers in Sevilla:

50% from giving the burghers estate control of the province (not important here);

50% from having a trade building (market place) built in Sevilla;

25% for Sevilla being a coastal province;

and some other modifiers that aren’t important to know what they are at this point (treasure fleet, mercantilism).

Summary: A province’s trade power comes from flat bonuses (development/5 + hardcoded “geographic” bonuses for certain provinces, usually called estuaries or coastal/inland centers of trade + etc.), which are then modified by trade buildings (e.g. market place) and other modifiers.  This gives us the provincial trade power created by a province.  (Note that there is no monthly or yearly rate of creation for trade power.  It’s just a number that represents the amount of “control” over the means of trade that that province provides for its country and ruler.)

There are two inherent parts to a trade node: its trade value and its trade power.  Note that in section I we started with a province’s trade value and trade power.  Now we’re going to trade nodes.

A trade node is basically a geographically partitioned region of the world.  Every province in the world is assigned to one and only one trade node.  So each trade node in the world is made up of a collection of neighboring provinces.  For example, the provinces of Granada and Sevilla and a bunch of other provinces on the Iberian Peninsula are part of the Sevilla trade node.  (The *province of Sevilla* is NOT the “capital” or “center” or anything like that of the *Sevilla trade node*.  The province of Sevilla is simply one province of many provinces that make up the trade node that’s located at the Iberian region.  That trade node just happens to also be called the “Sevilla trade node.”)

So a trade node is made up of a collection of provinces.  The sum of the trade values produced in all the provinces in a trade node is the trade value of that trade node.  Another name for this is the “Local” trade value of the trade node.

Screenshot II.a.1: Trade Value of a Trade Node.  Go to the trade map mode and click on the Sevilla trade node.  Hover over where it says “Local    +7.29” on the left.

Screenshot II.a.2: Trade Value of a Trade Node.  By hovering over the value of “Local,” we get a list of all the trade values of all the provinces in the Sevilla trade node.  We can find Granada’s trade value in the list, 0.30 monthly and 3.60 yearly.  The total monthly trade value of the Sevilla node contributed by the trade values of provinces in the node is 7.29.

Note that in a way, the trade value produced by a province has been double-counted in the game.  First, it turns into production income that the owner of the province earns directly (back to Screenshot I.a.3.):

But it also enters the trade node that the province is a part of and becomes this entity called Trade Value or “Local” Trade Value of a Trade Node (back to Screenshot II.a.2.):

The simple way to think about this is to pretend that each unit of salt in the game actually represents two portions of salt.  One portion is sold locally for cash and the other portion is shipped to the nearest major trading area, i.e. the trade node that the salt-producing province is a part of, where it’s sold to traders who are part of the global trading market.  Note that the first portion of salt has been immediately and fully converted to cash while the second portion of salt has entered the global market so that it’s likely that it will be sold and bought and sold and so on by different people anywhere in the world that trade flows to.  Who knows where that portion of salt will end up?  Note that we – rulers of this salt-producing province (e.g. Spain in the screenshots) – have not seen the cash revenue for this second portion of salt yet.  That is to be earned at a later stage of the trade game.

(A more precise way to think about this double-counting in my opinion is to pretend that production income from producing a good (the part that’s immediately converted to cash) is actually a “production tax” that you charge producers in your provinces.  For every unit of salt produced in a province, you charge the salt-producing factory 3.00 ducats as a production tax.  The salt-producer then sells that salt to some traders on boats, who move it around the world (the salt becomes trade value in a trade node).  At some point along this trip around the world, a ruler can charge a sales tax on the transaction of salt between merchants, also at 3.00 ducats per 1 unit of salt.  We haven’t gotten to the part yet about where and who can charge this sales tax on salt transactions.)

The trade power of a trade node is made up of different countries’ trade power in that node.  Here, it matters whose trade power a unit of trade power is (i.e. it matters now whether it’s Portugal’s trade power or Spain’s trade power in the Sevilla node).  Furthermore, trade power comes from different sources.  The different main sources are:

1) provincial trade power (as mentioned above in I.b),

3) light ships protecting trade in the trade node (if it’s a sea node), and

4) the presence or not of a merchant in the trade node (very small flat +2.0 trade power). Additionally, there is Caravan Power/Inland Trading bonus for steering on land routes, but this particular affect will be skipped in this guide. For an explanation of the effect: https://eu4.paradoxwikis.com/Trade#Caravan_power)

6) Also, there are events that just seemingly randomly give you bonuses out of thin air.  So we’ll just ignore these in this guide.  (These are likely hardcoded by the game for certain countries, like Spain getting trade bonuses for exploring the New World).

Note that provincial trade power in a trade node can only come from your owning a province in that trade node.  Everything that was used to explain I.b gives us this number for each province.  So, just for now, pretend that there is only provincial trade power and ignore all the other sources of 2) ~ 6) from above.  The state of trade power in the simplified Sevilla trade node would be like this:

Figure II.b.1: Provincial Trade Power in the Sevilla node.  Portugal holds 13.6/139.1 = 9.8% and Spain holds 125.5/139.1 = 90.2% of the trade power in the Sevilla node.

What the hell is “trade power transferring/propagating upstream?”  Different trade nodes are connected by links and each link has a direction of flow to it.  For example, the Tunis trade node is linked to the Sevilla trade node and has an arrow pointing from Tunis to Sevilla.  I.e., the Tunis trade node is upstream of the Sevilla trade node.

Screenshot II.b.2.1: The Tunis node upstream of the Sevilla node.

This is the game hardcoding that “trade wealth flows from Tunis to Sevilla.”  To put it another way, “trade in Sevilla is more powerful than in Tunis,” and one way this is manifested in the game is by this “trade power transferring/propagating upstream” mechanic.  What happens is that countries who have (at least 10) provincial trade power in Sevilla will have 20% of that provincial trade power in Sevilla “propagated” to upstream nodes like Tunis.  So out of nowhere, Spain gets 125.5 × 20% = 25.1 trade power in Tunis and Portugal gets 13.6 × 20% = 2.72 trade power in Tunis just because the arrow on the trade map mode points from Tunis to Sevilla.

Figure II.b.2.1: Provincial trade power of each country in a downstream node (Sevilla) is “propagated upstream” (to Tunis).  Note that Portugal’s trade power of 13.6 > 10, so it just barely made the cutoff for this upstream propagation.  If Portugal’s trade power were 9, then it would get 0 trade power propagated upstream to Tunis.

Summary: Tunis is upstream of Sevilla.  “Trade wealth” flows downstream from Sevilla to Tunis, i.e. trade in Sevilla is “more powerful” than trade in Tunis.  So having provincial trade power in Sevilla automatically grants you 20% of that amount of trade power up in Tunis.

This amount of upstream propagation from the Sevilla trade node is the same for all trade nodes that happen to be upstream of the Sevilla node.  The Safi, Ivory Coast, and Caribbean trade nodes are also upstream of the Sevilla node, so Spain and Portugal would also respectively get 25.1 and 2.72 trade power in every one of these nodes in addition to the Tunis node.  There is no propagation effect from Sevilla to any nodes that are downstream of it, like the Genoa node.  The upstream propagation only goes upstream by one link.  Thus, Spain’s provincial trade power in the Sevilla node that propagates up to the Tunis node won’t propagate further up to the Katsina node even though Katsina is upstream of Tunis.  (If Spain has provincial trade power in Tunis, then that amount of provincial trade power would propagate upstream to the Katsina node.)

Figure II.b.2.2: Upstream propagation is the same amount in all upstream nodes.

You can see how a country dominating (via having a lot of provincial trade power in) a trade node that is downstream to a lot of other nodes is powerful because that country will get bonus trade power in all those neighboring upstream trade nodes.  Note that it’s only *provincial* trade power in a trade node that gets this upstream propagation.

Screenshot II.b.2.2: Spain has 207.5 provincial trade power in the Sevilla node.  (That column tells us the amount of provincial trade power that each country has in the node.  I think the icon for the column is supposed to represent the shapes of provinces next to each other on a map.)

Screenshot II.b.2.3: Now, let’s look at the Safi node, which is upstream of the Sevilla node.  Mousing over the 166.5 in the right-most column (this column tells us the total trade power in the node of each country), we get a tooltip.  One of the items is “Transfers from traders downstream: +41.5”.  This comes from Spain’s provincial trade power downstream in the Sevilla node, where 207.5 × 20% = 41.5.  Spain having provincial trade power of 207.5 in the Sevilla node has given it 41.5 trade power in the Safi node.

Screenshot II.b.2.4: Looking at the Genoa node, here, Spain has 185.7 provincial trade power.  If you mouse over the blue arrow pointing left, it says, “Trade propagation reduction: -80%.”  I believe this is the game’s obscure, inscrutable way of telling us that there is 20% provincial trade power upstream propagation originating from here. In other words, 100% – 80% = 20% of Spain’s provincial trade power of 185.7 in the Genoa trade node, so that’s 185.7 × 20% = 37.51 is propagated to upstream trade nodes like the Sevilla trade node and the Tunis trade node.

Screenshot II.b.2.5: Looking at the Tunis node.  The Tunis node is directly upstream of both the Sevilla node and the Genoa node.  Thus, Spain has 207.5 × 20% (from Sevilla downstream) + 185.7 × 20% (from Genoa downstream) = 78.6 trade power in the Tunis node from “upstream propagation.”

Screenshot II.b.2.6: Going back to the Sevilla node, if you mouse over the yellow plus sign, the tooltip tells us nothing about the upstream propagation that is happening from here.  Both Genoa in the screenshot above and Sevilla here are nodes that are causing upstream propagation.  We’re mousing over the same location in the table, Spain’s second column from the left, yet we’re not getting info about the upstream propagation here in the Sevilla node screen.  This is why you can’t trust the tooltips.  (We’ll get to what the plus sign and the green arrows mean later.)

II.b.3,4,5) Other Sources of Trade Power

We also note that somehow, France, the Papal State, and Savoy have some trade power in this node, even though they have 1.) no provincial trade power and thus also 5.) can’t have their main trading city here to make it a home node, 3.) light ships, or 4.) merchants here (0s in those two columns).  Knowing all the above, we know that the only way they could have trade power here is by 2.) having provincial trade power in the Genoa node that’s propagating upstream to Sevilla or 6.) some other random bonuses, maybe from special events, who knows.

Screenshot III.1: The Basra node.  Basra has a link incoming from the Hormuz node (Basra is downstream of Hormuz) and outgoing links to the Aleppo and Persia nodes (Basra is upstream of Aleppo and Persia).

Note on the left the little table that lists Incoming, Local, Total, and Outgoing.  Whatever that all means…  But this is actually a crucial indicator that helps us understand what’s going on in a trade node.  These tell us the flow of *trade value* within a trade node.  “Incoming” is trade value that has somehow by some mechanic (to be explained soon) flown from upstream nodes (i.e. Hormuz) down into our node in question (Basra).  “Local” is what we figured out before in II.a: it’s the total trade value (aka “Local” trade value in a trade node) produced by provinces that are geographically located in this trade node.  Thus, “Incoming” + “Local” is the actual total trade value that exists in the trade node.  For Basra here, it’s 1.89 + 3.13 = 5.02 ducats.  (Ignore the “Total” label that appears in the table for now, as that will be explained soon.)

A) “Collect” it for income (either because that’s your home node where you automatically collect or because it’s not your home node but you place a merchant there to collect. The game calls both of these actions “collecting” or “retaining” trade value in the trade node.) (My intuitive interpretation of this action is that a Spanish merchant collecting in a node is a Spanish government representative placed there to collect sales tax on the trade occurring there between Spanish traders.)

B) “Transfer it downstream or steer it as it goes downstream” (or as the game calls it, “transfer trade power,” “transferring,” “transporting forward,” or “steering.” At times, these terms may be used interchangeably, although they shouldn’t be. There is “transferring” or what I would call passively transferring, and then there is “steering” (or what I might call actively steering to make the comparison complete). (My intuitive interpretation of a Spanish merchant steering trade in a node is that they are a Spanish government representative placed there to enforce a mercantilist policy of only allowing Spanish traders in this node to interact with other Spanish traders that do business in a downstream node. We will later see the difference between transferring and steering as well as hopefully understand why they are categorized together here.)

C) Not use your existing trade power in a node to claim any of the trade value there. (This occurs in a special situation, described in IV.b.1.) If this happens, other countries will still use their trade power in the node to proportionally claim that portion of trade value that you aren’t claiming.

The amount of trade value that has been steered/transferred to downstream nodes is the “Outgoing” amount in that table on the left side of the trade node screen and the amount of trade value that has been “retained” (i.e. collected) in a trade node is the “Total” amount in that table.  So “Incoming” + “Local” – “Outgoing” = “Total”.  This is the trade flow in a trade node.  I think of “Local” as “locally produced trade value” and “Total” as “remaining or collected trade value in the node.”  For Basra above, it’s “Incoming” (1.89) + “Local” (3.13) – “Outgoing” (2.66) = “Total” (2.35).

Screenshot III.2: Spain’s Trade Power in Basra.

Here, Spain has 38.2 trade power, seen in the right-most column of that table.  If I hover over the yellow portion in the pie chart on the right, it says “Spain has 22% of the Trade Power among countries Collecting from Trade.  Their trade power is 38.29.”  The first sentence is confusing.  Spain is not collecting from trade here.  We also see that in the map, in the top row of the sign/icon for the Basra node (around the center of the screen, a bit to the right), it says “38.2   (21%)”.  So some rounding of numbers is going on.  So ignore the confusion and just take the info that Spain has either 38.2 trade power here, which is 21% of the total trade power, or 38.29 trade power here, which is 22% of the total trade power.  Close enough.  Let’s go with the former.

From this info, what we know is that we can use our 21% of trade power in the Basra node to “claim” (and do something with) 21% of the total trade value in the Basra node.  Again, the total trade value that exists in the Basra node is “Incoming”(1.89) + “Local”(3.13) = 5.02 ducats.  So we have a claim to 5.02 × 21% ducats if all other countries are also claiming their share of the trade value here to either collect/“retain” or transfer downstream.  But if some countries aren’t claiming their share of trade value with their trade power, then there’s more trade value up for grabs for all the other countries that are claiming trade value.  (This situation will be described below in IV.b.1.)  So if Spain is collecting or transferring (in the screenshot, Spain is transferring in the node) and at least one other country is not claiming their share of trade value here, then Spain will be able to claim more than 5.02 × 21% ducats here.  Let’s look at all the possible actions for a country in a trade node.

IV Merchant Actions in a Trade Node

At a trade node, you can either have no merchant there, a merchant collecting there, or a merchant steering trade (“transferring trade power”) there.  Any country who has a trade node within its trade range can put a merchant there to collect or “transfer trade power”, so it’s very common for a given node to have many merchants there from different countries.  However, a country can at most place one of their merchants at a node (so you can’t both collect and transfer in a single node or put two merchants to simultaneously collect or simultaneously transfer there).  In end nodes, you can only place a merchant there to collect.  For your home node:

Let’s momentarily go back to the home node at Sevilla.  In your home node, you automatically collect from there even without a merchant.  If you place a merchant there to collect (and you can only choose to collect at your home node.  No transferring/steering), you get a 10% bonus to the amount of ducats you collect there.

Screenshot IV.a.1: Sevilla node.  In the first column of the table, you might see an icon of a house (meaning that a merchant is here collecting), an icon of a ship and wagon (a merchant is here transferring/steering), or a dash.  In the second column of the table, you might see either a yellow plus sign (collecting), a green arrow pointing right (transferring downstream), or a blue arrow pointing left (propagating upstream).  Here, we see that Spain has a dash and a yellow plus.  This is Spain’s home trading node, so Spain is collecting (the yellow plus) but has chosen not to place a merchant here for the 10% bonus income.  This is also Portugal’s home node, and we see that they are collecting (the yellow plus) and have placed a merchant here (the house icon) for the 10% bonus income.

Note however that Spain and Portugal also have provincial trade power here, so they are also propagating 20% of that trade power upstream, but the blue arrow pointing left isn’t shown anywhere.  Thus, don’t trust the tooltips.  Lack of a blue arrow doesn’t mean that countries here aren’t propagating trade power upstream.  But the two columns here do tell us the countries’ actions: Spain’s dash and plus sign mean that Spain has not placed a merchant here but is collecting here (which means that this must be Spain’s home node), while Portugal’s house icon and plus sign mean that Portugal has placed a merchant here for the +10% bonus to income (the house icon and yellow plus sign also means that this is Portugal’s home node. We will see later that a house icon and a green arrow pointing right means that the country has placed a merchant here to collect and this is not the country’s home node).

If you have no merchants collecting in any of your non-home trading nodes in the entire world, for every merchant that is transferring in any non-home node in the entire world, you get an extra +10% bonus trade power modifier in your home node.  Don’t ask me why.  Example:

Screenshot IV.a.2: We have no merchants collecting in any non-home nodes and have merchants transferring in Alexandria, Constantinople, and Safi.  The tooltip for Spain’s trade power modifier (mousing over where it says 111.9%) tells us that we get a +10% bonus to trade power in Spain’s home node of Sevilla for each of these three merchants transferring.  (The merchant in Alexandria is steering trade value to Genoa, which is downstream of Sevilla, so none of that trade value gets to Sevilla, yet we get this bonus in Sevilla.  Go figure.)

If you have even one merchant collecting in any non-home nodes in the entire world, no matter how many merchants you have transferring trade in non-home nodes, all of the abovementioned 10% bonus trade power modifiers in your home node disappear.  Don’t ask me why.

Example:

Screenshot IV.a.3: We have merchants in Tunis and Venice collecting.  The tooltip for Spain’s trade power modifier (where it says 81.9%) tells us that there is “No transfer bonus due to merchant collecting in Tunis.”  For whatever reason, we aren’t told that we also have a merchant collecting in Venice…  In any case, if there is even one merchant collecting anywhere in the world that is not your home node, this is what you’ll see in the home node trade power modifiers.

If you have a merchant collecting at your home node (i.e. providing you with a 10% bonus to trade income at your home node), this will not cause these +10% trade power bonuses at your home node from merchants transferring in other nodes to go away.  It is only if you have a merchant collecting in a non-home node that the +10% trade power bonuses at home go away.

Screenshot IV.a.4: We have a merchant collecting in Sevilla for the 10% bonus income at our home node, and merchants transferring in Alexandria, Constantinople, and Safi.  We still get the +10% bonus to trade power from each merchant transferring at those three nodes.

This means that there may be a moment in the game when you’re wondering tactically whether to collect from a non-home node for extra income or maintain all merchants to be transferring trade in different nodes so that you get this boost in trade value in your home node (and thus a boost to your income from your home node).

Screenshot IV.a.5: In the trade tab, the big number in the top-right tells you your total trade income.  Trade income comes from your automatic collection at your home node and other merchants collecting in non-home nodes.  The numbers on this screen (and many other numbers in the game) update on the first of every month.  So try different configurations for your merchants and see how the big number changes.  This trial and error is often the best way to tell what’s best for your country at the moment.

IV.b Non-Home Trading Node with No Merchant Collecting or Transferring There

I am going to call both your home node (where you automatically collect) and non-home nodes where you’ve placed a merchant to collect: “collection points” or “nodes that you collect in.”

IV.b.1 The Node is Not Upstream of Any of Your Collection Points, and You Don’t Have a Merchant There

If the node is not upstream of any of your collection points (even via multiple links) and you don’t have a merchant placed at that node, the game just assumes that you aren’t going to bother claiming trade value in that node.  This is the special situation mentioned in III C).

Figure IV.b.1.1: We collect in nodes A and B.  Node C goes to D, which goes to E, A, and J.  Node J is an end node.  Node E goes to B, which goes to G and H.  Node H also goes to A.  Node A goes to F, which then goes to K and L, which are end nodes.  Nodes C, D, E, and H are upstream of nodes we are collecting in (to be precise, C, D, E, and H are all upstream of at least one node we are collecting in).  Nodes F, G, L, K, and J are not upstream of any nodes we are collecting in.  This section is relevant to nodes like F, G, L, K, and J.  (Note that node H is downstream of a node we are collecting in, but as long as it is also upstream of a node we are collecting in, node A here, then it isn’t relevant to this section.  Also, I don’t say “nodes that are downstream of all nodes that you are collecting in,” since then:

Figure IV.b.1.2: assuming node A is an end node here, node G isn’t “downstream of all nodes you collect in” since it isn’t downstream of node A, but it’s still relevant here.  The technical point is that node G is not upstream of any of your collection points.

In a way, it makes sense that you might forfeit the use of your trade power in nodes F, G, L, K, and J.  If you don’t have a merchant collecting in F, G, L, K, or J, you aren’t trying to directly gain income there.  And if you don’t have a merchant transferring at F (you can’t place a merchant to transfer at end nodes K, L, G, or J), the game interprets that as your saying that you don’t care how the trade value flows after F since none of that trade value downstream of F can possibly get to any of your collection points anyway.  So for nodes F, G, L, K, and J, if you don’t have a merchant there, the game mechanic will automatically have you not use your trade power to claim your share of trade value there.

Screenshot IV.b.1.1: The Champagne node.  Spain has a dash and a blue arrow pointing left.  The blue arrow pointing left technically is supposed to mean that “Spain is transferring trade power upstream,” but this isn’t important nor helpful here, since Spain has 0 provincial trade power in Champagne here and is thus propagating 0 × 20% = 0 trade power to upstream nodes Rheinland and Bordeaux.  When you see a dash and a blue arrow in the same row, it means that the country has no merchant here and the node is not upstream of any of the country’s collection points.  I’m mousing over the yellow slice of the “Trade Power” pie chart.  Spain has 10% of the trade power in the Champagne node, but Spain is not using that 10% trade power to claim their share of the trade value here.

Screenshot IV.b.1.2: I’m mousing over the green pie of the “Retained Trade Value” pie chart.  It shows France with 54%.

Screenshot IV.b.1.3: I’m mousing over the red portion and it shows the Netherlands, Great Britain, the Papal State, and Savoy.

The “Retained Trade Value” pie chart is badly labeled.  I would call it “Claimed Trade Value.”  As you can see, Spain is missing from this pie chart as it wasn’t mentioned in the above 5 countries.  That’s because Spain hasn’t claimed its trade value here.  Green + red in that pie chart is the amount of trade value that has been claimed in this node by countries that are claiming here.  Green is the share of trade value that has been claimed and collected in this node (via automatic home node collection or non-home node merchant collecting) and Red is the share of trade value that is claimed and is being transferred or steered downstream.  Spain is not claiming any trade value here, so it isn’t part of this pie chart.

IV.b.2 The Node is Upstream of Any One of Your Collection Points, and You Don’t Have a Merchant There (and No One Else Has a Merchant Transferring There)

Back to Figure IV.b.1.1:

So now we’re talking about nodes C, D, E, and H.

Screenshot IV.b.2.1: Back to the Basra node.

Hormuz flows to Basra, which flows to Aleppo and Persia.  Basra is not my home node and I have no merchant there.  I have 22% of the trade power here.  Note for now how it says “We transfer 1.18 ducats to Aleppo,” whatever that means.

Screenshot IV.b.2.2: Note that the flags under the trade node’s “main sign”/icon or whatever it’s called (where it says “37.9 (21%)” on the first line and “2.3” on the second line) show the countries that either have a home node here or don’t have a home node here but have a merchant here collecting.  There are no flags under the two smaller signs each saying “1.32,” which means that there are no countries that have placed a merchant here to steer to Aleppo or Persia.

I’m currently mousing over the red part of the pie chart on the left.  Of the trade value in this node that has been claimed by countries, Spain has claimed 24% of that.  The total trade value in this node up for grabs is “Incoming” 1.86 + “Local” 3.13 = 4.99 ducats, so 4.99 × 24% = 1.20 ducats.  This is slightly off from 1.18 ducats but is probably from rounding that the game does.  So Spain has claimed 1.18 ducats of trade value in this node.  Other countries in this node that aren’t collecting but have claimed their trade values are Tabarestan and the Ottomans.  The red part of the pie chart is 53% of 4.99, so that is 4.99 × 53% = 2.64 ducats claimed by these three countries.  There are no merchants steering here, so Tabarestan and the Ottomans also simply don’t have a merchant here.  Note that Spain, Tabarestan, and the Ottomans all have a dash and then a green arrow pointing right in the first two columns.  This means that these countries don’t have a merchant here but are passively “transferring trade downstream.”  What this means is that the combined claims of Spain, Tabarestan, and Ottomans cause 2.64 ducats of trade value in this trade node to be transferred downstream (which is why it says “Outgoing: -2.64” on the left) without preference, i.e. equally between Aleppo and Persia.  That is why we see that 2.64/2 = 1.32 ducats are flowing each to Aleppo and Persia.  Of that 2.64 ducats that are “Outgoing,” Spain is causing 1.18 ducats of that.  That also means that Spain is causing 1.18/2 = 0.59 ducats to flow to each of Aleppo and Persia.  (This is why the “We transfer 1.18 ducats to Aleppo” message is confusing.  It should be something like “We cause (or “passively transfer”) 1.18 ducats to flow out of Basra downstream.  And in the tooltip, say: Specifically, 0.59 of that is going to Aleppo and 0.59 of that is going to Persia.”)

IV.c Non-Home Trading Node with a Merchant Transferring There

Now, let’s place a merchant in a node to “Transfer Trade Power” or what would preferably be called, steering trade.

Screenshot IV.c.a: I’m at the Basra node and click “Transfer Trade Power” and select a merchant.

Screenshot IV.c.b: Then I see this while I wait for the merchant to arrive in Basra.  I can’t choose whether to put him on the link to Aleppo or Persia while the merchant is still traveling.  (And if you try to send another merchant to Basra when the screen looks like this, the game will try, but in the end only the last merchant you send will matter.  The earlier merchants will magically teleport back to “Free” status.)  Once the merchant arrives, he’ll appear on one of the downstream links, and you can then instantaneously move him to steer on any one of the downstream links or to collect in the node, but you have to wait until the first of the next month to see the change in the numbers.

IV.c.1 Only One Merchant Transferring at a Node

Screenshot IV.c.1.1: Here, we have a merchant in Basra steering to Aleppo.  The “sign”/icon that says “3.03” is the link between Basra and Aleppo.  The red check mark means I have a merchant steering on this link.  Under that there is a small Spanish flag, showing that there is a Spanish merchant here.  Under the “sign”/icon that says “0.00” for the link between Basra and Persia, we see no flag underneath it, so there is no merchant steering here.  Note that in the table at the bottom-left of the screen, Spain has a “ship and wagon” icon and a green arrow pointing right.  This means that Spain has a merchant in this node steering trade.  We are the only one here with a merchant steering.

Note that the “Incoming”, “Local,” “Outgoing”, and “Total” numbers on the left have changed slightly from before due to some months passing.  Spain currently has 23% of the total trade power here and has claimed 25% of the trade value here.  So Spain has claimed [2.13 (“Incoming”) + 3.13 (“Local”)] × 25% = 1.31 ducats of trade value here.  Note how it says, “We transfer 1.31 ducats to Aleppo,” which I suppose can be interpreted to be technically not wrong.  Now we look at the sign that says “3.03.”  What has happened is that by having the only merchant here steering, Spain actually now gets to steer all 2.84 Outgoing ducats in the direction that Spain wants to direct them.  Even though Spain only has the trade power to claim 1.31 ducats here, Spain having the only merchant here steering overrules that in terms of steering trade, allowing Spain to decide where all the downstream trade goes to.  Other countries that have no merchants collecting or steering here but have claimed trade value with their trade power (Tabarestan and the Ottomans) cannot influence where their claimed trade value steers downstream to.  We have all 2.84 ducats going to Aleppo instead of divided equally between Aleppo and Persia due to the Spanish merchant steering here.  The growth of 2.84 to 3.03 is because:

Screenshot IV.c.1.2: I’m currently mousing over the “3.03.”  The first line of the tooltip is saying that 2.84 is the original amount of trade value that is “Outgoing” out of Basra.  The second line means that 100.00% of that is going to Aleppo due to the one Spanish merchant steering here.  The third line means that 53.90% of trade power among countries that are claiming trade value in this node (Spain, Tabarestan, and the Ottomans) are using it to transfer their claimed trade value downstream.  In other words, this just tells us the amount of the red portion of the pie chart on the left.  The fourth line tells us that the Spanish merchant somehow is able to apply a +6.90% bonus to the trade value that it steers from Basra to Aleppo.  This comes from:

Screenshot IV.c.1.3: In the trade tab, there’s an item called Trade Steering, which here shows 38.1% (coming from Spain’s Naval Tradition).  One merchant steering trade on a route applies a bonus of 5% to the trade value × a Trade Steering modifier.  So 5% × (1 + 38.1%) = 6.90%.  (Although the Trade Steering bonus comes from Naval Tradition, it applies to any link between nodes that your merchant is steering, even when steering from an inland node to another inland node.  Shrug.)

IV.c.2 Merchants Working in Different Directions

If one merchant is steering trade in one direction and another merchant in another direction, the two countries of those merchants will fight over the “Outgoing” trade value using their country’s trade power in the node to determine how much of the trade value flows to where.  Countries who don’t have merchants collecting or steering in the node will have their claimed trade value passively “transferring” downstream – as described in the previous section – and can’t decide where their outgoing trade value flows to.  Let’s look at it in action.

Screenshot IV.c.2.1: Let’s look at the Tunis node.  There are a bunch of countries collecting here (either because it’s their home node or it isn’t their home node but they have placed a merchant here to collect).  Portugal is the only country steering, and it’s steering trade to the Sevilla node.  Because it’s the only one steering here, 4.30 ducats are going to Sevilla and 0.00 are going to Genoa.  Let’s place a merchant here to steer towards Genoa.

Screenshot IV.c.2.2: Our merchant is at Tunis steering towards Genoa.  I’m mousing over the “0.83” that’s highlighted with a red oval and box, the Tunis to Sevilla route.  What the tooltip tells us is that of all of the 4.09 “Outgoing” trade value, 19.50% of that is going to Sevilla (4.09 × 19.50% × (1 + 5.20% from Portugal’s merchant steering bonus) ≈ 0.83 ducats).  Of all the trade value that initially exists at Tunis, which is 0.00 “Incoming” + 4.93 “Local” = 4.93, then 83.00% of that has been claimed by countries that are steering or letting it transfer downstream.  (Thus, 4.93 × 83.00% = 4.09 ducats have been claimed by countries that are letting it transfer downstream, aka the “Outgoing.”) And the Portuguese merchant has a 5.20% bonus to trade value that he steers.

Screenshot IV.c.2.3: I’m now mousing over the “3.52” that’s highlighted with a red oval and box, the Tunis to Genoa route.  What the tooltip tells us is that of all of the 4.09 “Outgoing” trade value, 80.40% of that is going to Genoa (4.09 × 80.40% × (1 + 6.90% from Spain’s merchant steering bonus) ≈ 3.52 ducats).  Of all the trade value that initially exists at Tunis, which again is 0.00 “Incoming” + 4.93 “Local” = 4.93, 83.00% of that has been claimed by countries that are letting it transfer downstream (this is the same as the above.  Hasn’t changed).  And the Spanish merchant has a 6.90% bonus to trade value that he steers.

IV.c.3 Merchants Working in the Same Direction

What if Spain and Portugal both steer trade from Tunis to Sevilla?

Screenshot IV.c.3: Now, both the Spanish and the Portuguese merchant are steering towards Sevilla.  I’m mousing over the 4.45.  Below that, we see both the Spanish and Portuguese flags, showing that these two merchants are steering on this link.  Of the Outgoing 4.10 ducats, 100.00% of that is going on this route.  Now what happens is that the bonuses that each merchant applies to the trade value on this link changes.  The first merchant still starts at 5% modified by their country’s Trade Steering bonus (Portugal), resulting in 5.20%.  The second merchant starts at 2.5% modified by their country’s Trade Steering bonus, so for Spain we have 2.5% × (1 + 38.1%) = 3.4%.  This goes on until the fifth merchant steering on the same link.  For more: http://www.eu4wiki.com/Trade#Multiple_merchant_bonus.

IV.d Non-Home Trading Node with a Merchant Collecting There

When placing a merchant to collect in a non-home node, your trade power in the node is halved, and then that amount of trade power is used to claim trade value for direct income, plus modifiers (that are called Trade Efficiency in the game).

Screenshot IV.d.1: Now, let’s have our merchant in Tunis collect there.  I’m mousing over the 106.6.  Note that our trade power here has halved compared to the 213.3 trade power from the previous screen when we were transferring trade.  Somehow our modifier here is -11.3%, shown in the column to the left.  We’ll mouse over that in the next screenshot.  Now that we are collecting here (with our halved trade power), we are now one of the countries that is “retaining” trade value here, so note how the green in the pie chart on the left has increased compared to before.  Also, using our trade power, we have shifted trade value from “Outgoing” to “Total.”  Spain’s icons down in the table, a house icon and a green arrow pointing right, means that there is a merchant here collecting in a non-home node.  It doesn’t make sense why it’s still the green arrow (which is supposed to mean transferring trade downstream).

Screenshot IV.d.2: Mousing over the -11.3% now.  Our total positive (green) modifiers here are +77.4%.  So when we didn’t have a merchant collecting here, we had: 120.2 trade power from trade power sources × 177.4% modifiers = 213.3 trade power.  Our halving modifier from collecting here is applied to this final 213.3 and thus takes away 213.3/2 = 106.6 trade power.  So, effectively, if we pretended that this halving modifier was an additive modifier like the other green modifiers that get applied to the original 120.2 trade power, it is doing -106.6/120.2 = -88.7%.  Thus, our total additive modifiers is +77.4% – 88.7% = -11.3%.  Thus, the halving modifier is (confusingly) expressed as -88.7% in the tooltip.

Summary: So first, as noted in IV.a, a merchant collecting in any non-home node voids all possible +10% bonuses to trading power at your home node that come from other merchants transferring in other nodes.  Second, as noted here, a merchant collecting in a non-home node also first reduces your trade power there by half before you get to collect trade value as income.

V Tactics and Strategy

The simplest ways to increase trade power in a node is to increase provincial trade power by conquering other provinces in the node, increasing trade power in the provinces (buildings, modifiers like mercantilism), and building light ships to protect trade in the node if it’s a sea node.  You should mainly target provinces in a node that have those hardcoded bonuses, like estuaries and “centers of trade,” as those flat bonuses pretty much always make them the key provinces to control in the node for the sake of trade power.  Just owning those few provinces in the node can often get you majority trade power in the node.

V.b Basic Steering

Back to Figure IV.b.1.1.  We collect in nodes A and B.  Assume that there are no other merchants from other countries steering at any nodes in the figure.  So D’s “Outgoing” is divided equally between J, A, and E.  If we were to place a merchant at node D to steer trade, in which direction would we want to steer it to?

Clearly not J, since then the trade value isn’t going anywhere that we’re collecting.  If J wasn’t an end node and instead led to other downstream nodes but none of them led to our collection nodes, we still know that we wouldn’t want to steer to J.  We want to steer trade value towards our collection nodes – this is basic steering.

How to choose between steering to A or E?

See Appendix below for unnecessary math used to show that:

**The answer is not J and then trial and error between A and E by looking at the trade tab on the first of the month, lol.**

V.c Steering Towards Your Home Node or Collecting at a Non-Home Node.  A Trade Power Threshold for Your Home Node?

Early on, you might have a home node and one other non-home node and you might have decent trade power in both.  Should you use a merchant in the non-home node to transfer towards your home node or should you collect at that non-home node?  This is a question I had from the get-go and is also a common question I see by others, and for good reason, since it’s basically what you encounter at the beginning of the game.

See Appendix below for unnecessary math used to show that:

**The answer is use trial and error by looking at the trade tab on the first of the month, lol.  The best answer to this question is “just try both out.”**

V.d What To Do About Nodes that Aren’t Upstream of Any of Your Collection Points

Back to Figure IV.b.1.1: I’m talking about those F, G, L, K, and J nodes.  I’ll also call these nodes “strictly downstream” nodes just because it’s less unwieldy.

If you aren’t worried about the erasure of the +10% trade power bonuses at home from merchants transferring at other nodes, you can collect at these strictly downstream nodes.  It’s a comparison of whether you have enough trade power at the strictly downstream nodes to warrant a merchant collecting there, or if your home node is rich enough in trade value and you have enough pre-modified trade power at your home node such that those +10% bonuses in trade power at home get you more income than what you can collect at the downstream nodes.

If F connects to further downstream nodes and there are rivals you are competing against that are collecting either at F or further downstream:

if there are rivals downstream of F, you might place a merchant to steer trade at F if you can steer it away from their collection nodes or at least in a way that it helps your rivals the least;

if there are rivals collecting at F, you might place a merchant at F simply to steer it in any direction downstream so that at least you’re claiming your trade value there and letting it flow out of F (remember that if you don’t place a merchant at a node that is strictly downstream of your collection points, the game will cause your country to not claim any of the trade value there).

Note that as long as you dominate your home node of A (say you basically have 100% trade power there), then you’ll simply collect all the trade value that’s flowing to A and none of it will flow downstream to F.  Increasing your trade power % in A is the best, but increasing in both A and F are useful.

V.e Web/Net vs. Trail/Route

VI Other Stuff

Other Recommended Guides:

A comprehensive guide with screenshots.  Also, check out /u/Llama-Guy’s comment where he makes some points.

/u/issoweilsosoll’s Trade – a case study

The final form of the trade “trail” strategy.  The real TL;DR of trade in EU4 is to try to copy this, basically.  Even if you don’t understand or don’t want to understand any of the details of trade mechanics, this guide and demonstration alone will help a lot for the general feeling.

Don’t use the version at the top of that page.  Use this corrected version in the comments here:

VII Appendix

The following isn’t recommended if you aren’t interested in pointless math.

V.b Basic Steering

Back to Figure IV.b.1.1.  We collect in nodes A and B.  Assume that there are no other merchants from other countries steering at any nodes in the figure.  So D’s Outgoing is divided equally between J, A, and E.  If we were to place a merchant at node D to steer trade, in which direction would we want to steer it to?

Clearly not J, since then the trade value isn’t going anywhere that we’re collecting.  If J wasn’t an end node and instead led to other downstream nodes but none of them led to our collection nodes, we still know that we wouldn’t want to steer to J.  We want to steer trade value towards our collection nodes – this is basic steering.

How to choose between steering to A or E?

Which is larger,

(2/3 × D’s Outgoing) × (our trade power % in A)

vs.

(2/3 × D’s Outgoing) × (trade power % of countries in E that are transferring trade value downstream) × (our trade power % in B)?

Rearranging, we get:

(Our trade power % in A) vs. (trade power % of countries in E that are transferring trade value downstream) × (our trade power % in B),

where if the first is larger, we transfer to A, and if the second is larger, we transfer to E.  Where do we steer?

**The answer is not J and then trial and error between A and E by looking at the trade tab on the first of the month, lol.**

You can do the math in the last equation above, but in-game, modifiers and other nations steering and whatnot are gonna screw with the final result.  But the basic conclusion is as expected (and a bit obvious), which is that in a chain of trade nodes, trade value originating from a far-away node gets multiplied by (trade power % in in-between nodes that are transferring trade value downstream) (which will always be ≤ 1, of course) at each in-between node.  So to maintain a chain of trade value flowing back to your home node, you want to try to dominate every one of those trade nodes.

V.c Steering Towards Your Home Node or Collecting at a Non-Home Node.  A Trade Power Threshold for Your Home Node?

Early on, you might have a home node and one other non-home node and you might have decent trade power in both.  Should you use a merchant in the non-home node to transfer towards your home node or should you collect at that non-home node?  This is a question I had from the get-go and is also a common question I see by others, and for good reason, since it’s basically what you encounter at the beginning of the game.

A’s “Incoming” (trade value) × Our trade power % at A =

A’s “Incoming” × x =

“B’s “Outgoing” × x =

(B’s “Incoming” + “Local”) × (Trade power % at B of all countries transferring downstream) × x =

(B’s “Incoming” + “Local”) × (Our trade power % at B + trade power % at B of other countries transferring downstream) × x =

(B’s “Incoming” + “Local”) × (Y/(Y + U + V) + V/(Y + U + V)) × x

If we collect at B, y goes down by some amount to a new value, which we’ll call y’ (aka “y prime”).  We have y’ = (Y/2)/(Y/2 + U + V).

(The change from y to y’ is an amount that is hard to predict.  We have:

y = Y/(Y + U + V), so U + V = Y/y – Y

y’ = (Y/2)/(Y/2 + U + V) = (Y/2)/(Y/2 + (U + V)) = (Y/2)/(Y/2 + Y/y – Y) = (1/2)/(1/2 + 1/y – 1) = (1/2)/(1/y – 1/2) = 1/(2/y – 1)

Plotting this gives:

https://www.wolframalpha.com/input/?i=plot+1%2F(2%2Fx+-+1)+from+x+%3D+0+to+1

where the horizontal axis is y before collecting and the vertical axis is y’.  Generally, y’ is about 0 to 0.17 below y.  Here is another way to look at it:

https://www.wolframalpha.com/input/?i=plot+(1%2F(2%2Fx+-+1))%2Fx+from+x+%3D+0+to+1

where the horizontal axis is y before collecting and the vertical axis is y’/y.  So when y starts out large (near 1), y’ is also not that much smaller.  But when y is small, y’ can be almost half of y.)

The amount of trade value flowing from B to A coming from our trade power at B disappears (since we are now collecting at B).  Our trade power of Y/2 at B is now used to collect.  A trade power of U is still collecting at B (the other countries collecting there), and a trade power of V is still transferring trade downstream at B (the other countries transferring downstream there).  So now, V/(Y/2 + U + V) is the share of trade power used to transfer trade value from B down to A.  So the amount of income we earn at A due to trade flow from B to A is:

(B’s “Incoming” + “Local”) × V/(Y/2 + U + V) × x

The amount of income we earn at B due to collecting at B is:

(B’s “Incoming” + “Local”) × (Y/2)/(Y/2 + U + V) =

(B’s “Incoming” + “Local”) × y’

Thus, (Income due to trade flow from B to A while collecting at B) vs. (Income due to trade flow from B to A without a merchant at B) is:

(Income from collecting at B) + (Income at A due to trade flow from B to A) vs. (Income at A due to trade flow from B to A without collecting at B)

After dividing (B’s “Incoming” + “Local”) from both sides of the “vs.”:

(Y/2)/(Y/2 + U + V) + V/(Y/2 + U + V) × x vs. (Y/(Y + U + V) + V/(Y + U + V)) × x

(If you want to change the right-hand side to (Income due to trade flow from B to A with a merchant steering from B to A), you can add a 1.05 multiplier to that side, but I won’t do that here.  Continued:)

(Y/2)/(Y/2 + U + V) + V/(Y/2 + U + V) × x vs. (1 – U/(Y + U + V)) × x

(Y/2)/(Y/2 + U + V) vs. (1 – U/(Y + U + V)) – V/(Y/2 + U + V)) × x

If we let u = U/(Y + U + V), u’ = U/(Y/2 + U + V), and v’ = V/(Y/2 + U + V), we have:

y’ vs. (1 – u – v’) × x

y’ vs. (1 – (u + v’)) × x

Note that while u’ > u and v’ > v, it’s always true that 1 ≥ u’ + v’.  So 1 ≥ u + v’ and thus (1 – (u + v’)) ≥ 0.

Let’s say we dominate trade power in B.  That means both u and v’ are small so that (1 – (u + v’)) is close to 1, so we basically have something close to

y’ vs. x

If y’ is larger than x, then we collect at B.  Otherwise, we don’t collect at B.  y’ is our post-collection trade power % at B, so it’s simply saying that if we dominate trade at B so much that our post-collection trade power % at B is larger than our trade power % at A, then collect at B.  (This is probably unlikely since usually, you have more trade power % at your home node A when you start the game.)  If we dominate trade power at B even post-collection but we also dominate at A, then it’s a straight comparison between these two values.

Back to y’ vs. (1 – (u + v’)) × x

If we don’t dominate trade power in B, u + v’ is larger, (1 – (u + v’)) becomes smaller, and so the left-hand side becomes relatively larger, meaning that collection at B becomes more likely to be better compared to when we did dominate trade power in B.  However, of course, this all depends on x, our trade power % at our home node A, which is likely to be larger than y or y’ in most early game periods.  What the above is saying is that if we don’t dominate at B (and thus (1 – (u + v’)) is some value between 0 and 1), but we are strong enough at A (x is large), it’s still better not to collect at B.  But if we aren’t strong enough at A, then it’s better to collect at B by just locking in an income at B instead of letting it flow to A and fighting over it again with our trade power % of x at A.

A simple example with numbers: say that at node B, we have 10 trade power. Other countries transferring trade downstream at B have 10 trade power, and other countries collecting at B have 20 trade power.  So we have 10/40 trade power at B, or 25%.  As long as we are not collecting at B, (10 + 10)/40 = 50% of trade power at B is being used to transfer downstream and 20/40 = 50% to collect at B.  Our current income at A is (B’s Incoming + Local) × 50% × x.  Once we’re collecting at B, we have 5 trade power at B, giving us 5/35 = 14% trade power share at B.  There is 10/35 = 29% trade power share of other countries still transferring trade downstream at B now.  So our income at A now is (B’s Incoming + Local) × 29% × x and our income at B is (B’s Incoming + Local) × 14%.

So income during collection at B is 0.14 + 0.29 × x and income before collection was 0.50 × x.  When x < 0.66, it’s better to collect at B, and when x > 0.66, it’s better to not collect at B.  This shows us that even if you have 25% trade power at B, to make it worth steering from B to A in the purest circumstances (instead of collecting at B), you need more than 66% trade power at A.  Otherwise, just collect at B.

For a more realistic/general situation, let’s say node B is upstream of node A and but has b downstream links, one of which is to A.  Like before, we have y trade power % at B, coming from Y trade power that we have, U trade power of other countries collecting, and V trade power of other countries transferring trade downstream so y = Y/(Y + U + V).  Again, assume that there are no merchants steering at B.  So initially, trade value of 1/b × B’s Outgoing is flowing to each of B’s downstream nodes, including A.  Including the 5% bonus that a merchant steering gives to trade value on its link:

Placing a merchant to collect at B vs. Placing a merchant at B to steer from B to A:

(Income from collecting at B) + (Income at A due to trade flow from B to A) vs. (Income at A due to trade flow from B to A with merchant steering from B to A):

(Y/2)/(Y/2 + U + V) + (1/b) × V/(Y/2 + U + V) × x vs. 1 × (Y/(Y + U + V) + V/(Y + U + V)) × x × (1 + 5%)

y’ + (1/b) × v’ × x vs. 1 × (1 – u) × x × (1 + 5%)

Now even more generally, allow merchants from other countries to steer at B, let f = the percent of (B’s Incoming + Local) that flows to A when we have a merchant collecting at B, let g = the percent of (B’s Incoming + Local) that flows to A when we have a merchant steering from B to A, let h = the sum of additional percent bonuses that other countries’ merchants steering on the B to A route provide to trade value on that link, and j = the additional bonus percent we provide to the trade value in the B to A link by placing our merchant to steer on that link.  Then, we have:

y’ + f × (1 + h) × x vs. g × (1 – u) × (1 + h + j) × x

So how do we choose what to do?

**The answer is use trial and error by looking at the trade tab on the first of the month, lol.  The best answer to this question is “just try both out.”**

The intuition provided by the above simple example (the one with x > 0.66) probably still holds though, which is that domination of your home node is the most important thing to have when you want to start thinking about a global steering strategy.  Next most important would be domination at your nodes closest to your home node in the connections, and so on.  If A is your home node and A <- B <- C <- D, dominating trade power in C doesn’t help as much if you aren’t also dominating trade power in B, and of course most of all at A.  Until you can dominate trade power at your home node A, mindlessly collecting at all non-homes nodes with your merchants could be worth it.

Here is a messy in-game example:

Table 1, “Attempting Optimal Balance”

Spain’s home node is Sevilla, where it has no merchant, and then it has 9 merchants in non-home nodes that I generally felt were where Spain had the best presence.  Other than Sevilla, Spain is collecting in Genoa and Constantinople since it has decent trade power in those high trade value nodes.  The other merchants are generally steering towards one of these collection points.  Ignoring modifiers and bonuses, total trade income from the three collection points is 17.68 + 8.68 + 9.86 = 36.22.  In-game, with all the modifiers and bonuses obviously, the total trade income was actually 63.43.

Table 2, “All Collecting”

I then switched things so that all 9 merchants are collecting in non-home nodes.  Ignoring modifiers and bonuses, total trade income from the ten collection points is 39.23.  If we choose to take the merchant in Ragusa (who is collecting the least) and put him in Sevilla for the 10% income bonus at home there, the total trade income becomes 40.88.  In-game, with all the modifiers obviously, the total trade income was actually around 61.8 with a collector at Ragusa and 62.3 after moving him to Sevilla.

(Also, for a moment, let’s take away Constantinople and Genoa and pretend that those two nodes are completely off-limits to us (since including them makes collecting from them obviously lucrative).  In such a scenario, only our home node of Sevilla is a node where we have a lot of trade power and that has a lot of trade value.  Then, having all merchants steering (to get the bonus trade power at the home node of Sevilla) should be better than having all merchants collecting in the other less valuable nodes.  If we have a very significant presence (but not totally overwhelming dominance that is close to 100%) at our home node and at all other trade nodes we have either little trade power or the nodes are poor in trade value, every bit of additional trade power at home increases our income a lot there.  Thus, we’d basically be placing merchants to steer at other nodes more for the bonus to income at home than the additional trade value that gets steered to our home node.)

What I’m trying to demonstrate is not necessarily the differences in total income between the scenarios, but how similar the incomes are despite the first strategy attempting an optimal balance between collecting and funneling, the second briefly-described and approximated strategy of steering everywhere and only collecting at home, and the third strategy of blindly “collect everywhere, forget about steering.”  But it’s another example of how real domination of your home trading node (or collection points in general) is needed before worldwide trade-steering strategy becomes much more important and powerful than ignoring everything and simply collecting with all your merchants even though it may feel like the least strategic method.  The real answer to all of this is still to just do trial and error, of course.