In this guide I will talk about buildings that raise provincial Trade Power: Marketplaces, Trade Depots and Stock Exchanges.

Before we begin, there are some messy game terminologies that we need to sort out. There are 3 types of trade-related modifiers in EU4 and it is important to tell them apart. I know it's confusing, but hey welcome to EU4 trade mechanics.

1. Provincial Trade Power modifiers: modify Trade Powers of individual provinces. Examples include Colonialism Institution bonus (+10%), Mercantilism, province controlled by Burghers (+50%) and Trade Power buildings.


2. Node Trade Power modifiers: modify a nation's Trade Power in individual Nodes. Examples include Global Trade Power (provided by Stability, Prestige, Power Projection etc.), Maximise Profit Trading Policy (+5%) and collecting at non-home Nodes (-50% multiplicative).

Note that "Global Trade Power" and "Node Trade Power modifier" are not the same. Global Trade Power is a collection of modifiers that affect all Nodes equally where you have Trade Power, and is a subset of Node Trade Power modifiers.

BTW there is an error in the way the Node Trade Power modifiers are displayed - it will be covered later in this guide.

3. Node Trade income modifiers: convert Trade Value collected in a Node into actual Trade income. Examples include Trade Efficiency (provided by Advisors, Diplomatic Technology etc.) and Merchant being present in the Node (+10%).

Note that "Trade Efficiency" and "Node Trade income modifier" are not the same. Trade Efficiency is a collection of modifiers that affect all Nodes equally where you are collecting from trade, and is a subset of Node Trade income modifiers.

This is an Excel table summarising the various trade-related modifiers (examples are not exhaustive).

• Autonomy (affects provincial Trade Power) and 'collecting at non-home Nodes' (affects Node Trade Power) are multiplicative modifiers. The rest are additive.
  
• Trade Power buildings - the topic of this guide - affect provincial Trade Power, affecting individual provinces.

Next, there are some glitches in the game that I need to go through.

Provincial Trade Powers are displayed inaccurately on the 1 Nov 1444 start date. It takes a month for the errors to update to the correct values. For example see Reims below:


TP of Reims should be 13.2 x 1.2 x 0.875 = 13.86, but that's not right. Let a month pass..


Attaboy!

Because of this glitch, I will be using France on 1 Dec 1444 for my Excel tables in this guide, not 1 Nov 1444.


That leads me to something else that is quite funny and needs mentioning - the way province autonomies are displayed in-game. For example see Valois on the 1 Dec 1444:


It says province autonomy is 1.9%. No it's not. Reims' autonomy on the 1 Nov 1444 was 2.0%, and it decreases by 0.125% every month. So on the 1 Dec 1444, the actual province autonomy is
2% - 0.125% = 1.875%.
This value is rounded up and displayed as 1.9% in the province tab. But in the detailed autonomy tooltip, the penalties from province autonomy are displayed as 1.8% (rounded down from 1.875).
Local Trade Power is penalised by half of autonomy, so the penalty is 1.875/2 = 0.9375%, which is displayed as 0.9%.

Marketplaces become available at Diplo Tech 4 (Year 1453), cost $100 and raise provincial Trade Powers by 50%.

Trade Depots become available at Diplo Tech 17 (Year 1622), cost $300 and raise provincial Trade Powers by 100%.

Stock Exchanges become available at Diplo Tech 22 (Year 1687), cost $400 and raise provincial Trade Power by 125%.

Open the Buildings tab, click Marketplace, and align the provinces by Improvement value.

Lyonnais is supposed to be the most cost-efficient province to construct a Marketplace. It is projected to raise provincial Trade Power by 7, the highest out of all candidates. A high rise in provincial Trade Power, however, does not necessarily correspond to a high rise in Trade income, because Trade income depends on many other factors.

The lists of suggested provinces are identical, as they should be, for Trade Depots and Stock Exchanges.

Here is an Excel table calculating the actual changes in provincial Trade Power for the top 10 provinces from the list, from Lyonnais to Toulouse. Scenarios with Marketplaces, Trade Depots, and Stock Exchanges are all in this table.

• Base TP = Base Trade Power, before any modifiers are applied
  
• TPmod = Provincial Trade Power modifiers (excluding autonomy)
  
• TP = Provincial Trade Power, after applying modifiers and autonomy.
  
• dTP = Difference in provincial Trade Power after constructing a building
  
• Autonomy is ignored for provinces controlled by Burghers (eg. Lyonnais).

For example, in Reims:
Trade Power = 13.2 (base Trade Power) x 120% (Trade Power modifiers) x (1 - 0.25/2) (from autonomy) = 13.86
Note that Trade Power is affected by half of a province's autonomy.

Some cells are highlighted in red - it means that the predicted increments given by the game do not match the actual increases in Trade Power. For example, Trade Power of Reims with a Marketplace should be 19.635, an increase of 5.775, but the game tab displays it as 5.76.

That is an error. It should be 5.77, not 5.76. I know it's a tiny difference, but still.

Despite minor inaccuracies, the provinces are still aligned in the correct order, so you can still follow the list when choosing a province to construct a Trade Power building.

Note that Colonialism Institution gives +10% provincial Trade Power. Colonialism Institution spawns in 1500, so the +10% modifier will apply for the majority of your campaign.

Next, I will evaluate how changes in provincial Trade Power translate into actual changes in Trade income.

Due to the large amount of work required, calculations are done only for 2 provinces, Lyonnais and Reims.

Lyonnais is part of Genoa Node. On 1 Dec 1444, France is collecting trade from Genoa, a non-home Node, using a Merchant .
Reims is part of Champagne node. France is collecting trade from Champagne, a home Node, without a Merchant.




The following is a glossary of the terms used in the tables above, and where the necessary values were acquired:

• Province TP = Trade Power of province
  
• dTP = Difference in provincial Trade Power after constructing a building
  
• Node total TP = Total Trade Power of the Node. The base values (when no buildings are present) are taken from the Trade Nodes tab.
  
  
• TP of collectors = Total Trade Power of all nations collecting trade from the node.
  Genoa is an end-Node, so 100% of Trade Power is used to collect. For Genoa, Node total TP = TP of collectors.
  
  
  In Champagne Node, 40.1% of Node Trade Power belongs to steering nations, and 59.9% to collecting nations. These values can be found by hovering your mouse over a link that connects Champagne to a downstream Node. It says that 40.1% of Trade Power is used to steer trade out from Champagne.
  The same information can also be found from the pie chart in the Node tab, but this is less accurate compared to the value acquired from the trade link.
  
  
  
• French TP = Trade Power of France in the two Nodes. Detailed breakdowns are given in the tooltips of individual Node tabs.
  French TP breakdown for Genoa Node
  
  Node Trade Power modifier breakdown for Genoa Node
  
  In the Introduction, I mentioned that there are 3 types of trade-related modifiers. The modifiers listed here are the second type - Node Trade Power modifiers.
  
  There are errors in these tooltips.
  
  
  Instead of describing what's wrong, I will just write here the correct formula for calculating French Trade Power in Genoa Node.
  
  Trade Power from provinces: 39.2
  Trade Power from having a Merchant in the node: 2
  Node Trade Power modifiers (additive): 3.8% from Power Projection, 1.3% from Prestige, 5% from Maximise Profit Trading Policy
  Node Trade Power modifier (multiplicative): -50% for collecting at a non-home Node
  
  Therefore, French Trade Power in Genoa Node:
  (39.2 + 2) x (100% + 3.8% + 1.3% + 5%) x 0.5 = 22.6806
  OR
  (39.2 + 2) x 0.5505 = 22.6806
  OR
  (39.2 + 2) x (1 - 0.4495) = 22.6806
  
  
• Node total TV = Incoming Trade Value + Locally produced Trade Value in the Node.
  
• Node retained TV = Incoming Trade Value + Locally produced Trade Value - Outgoing Trade Value.
  This is the Trade Value breakdown for Genoa Node. There are 2 errors in the tooltip.
  
  1. It should 'Retained' and not 'Total' because the value displayed here is the retained Trade Value after subtracting the outgoing Trade Value.
  2. The tooltip says 'Total Value of local trade node and incoming Trade Value'. This is wrong. It should say, 'Retained value of local and incoming Trade Value, AFTER subtracting outgoing Trade Value'.
  
  
• French collection = amount of Trade Value collected by France, before any income modifiers are applied.
  Trade collection for France in Genoa Node:
  
  
• Income modifier = used to convert the Trade Value collected by France into an actual income. Out of the 3 trade-related modifiers described in the Introduction, this is the third - Node trade income modifier.
  
  Node trade income modifier is 1.22 in Genoa Node (+0.1 from Burghers, +0.1 from having a Merchant present in the Node, +0.02 from Diplo Tech), but I used 1.34 in my Excel table (+0.1 from Burghers, +0.1 from having a Merchant present in the Node, +0.14 from Diplo Tech). Node trade income modifier is 1.12 in Champagne Node (+0.1 from Burghers, +0.02 from Diplo Tech), but I used 1.24 in my Excel table (+0.1 from Burghers, +0.14 from Diplo Tech).
  
  The reason I used +0.14 from Diplomatic Technology is explained in the previous guide, EU4 Advanced Economics 2. Buildings Part I.
  
  
• $T/m = Monthly Trade income in the Node
  
• d$T/m = Difference in monthly Trade income in the Node, after the construction of a building
  
• (d$T/m)/Cost = Difference in monthly Trade income in the Node, divided by the construction cost ($95 for Marketplaces, $285 for Trade Depots, $380 for Stock Exchanges). -5% construction cost assumed from Renaissance Institution.
  
• ROI(yrs) = Return on investment. Number of years it takes for the building to start producing profit i.e. to break-even. Decimal points omitted. Note that the 1-year construction period is not considered, so you need to add 1 more year if you want to count from the construction start date.
  
• Last profitable year = the last date when the building can be finished and still expect a profit before the campaign ends in 1821. Not applicable in non-Ironman games. Decimal points omitted.
  
  
• There is an additional note to be made regarding Reims. When the Trade Power of France goes up in Champagne Node, France will collect more income there. But since less Trade Value will flow from Champagne to Genoa Node, France will consequently collect less income from Genoa.
  
• The Excel table above for Reims does not take this into account, so it will overestimate the boost in Trade income by a very slight amount. I calculated the exact changes in Genoa Node using a separate Excel spreadsheet and they did not change the ROI years of Trade Power buildings in Reims by more than a year.
  
  All in all, constructing Trade buildings in Lyonnais is more cost-efficient than constructing them in Reims. Marketplaces are shown to be more efficient than Trade Depots or Stock Exchanges.

• Based on the examples used in this guide, Trade buildings show a similar cost-efficiency compared to Tax/Production Efficiency buildings. For example. building a Workshop in Lyonnais boosts Production income by $0.22/month and has a ROI of 36 years (these values are from the previous guide, EU4 Advanced Economics 2. Buildings Part I). On the other hand, a Marketplace in Lyonnais boosts Trade income by $0.18/month and has a ROI of 43 years.
  
• This shows that a strategically located Trade Power building can be a sound investment, especially considering that Trade becomes the most important source of income in the late game. They also synergise well with Manufactories.
  
• The main advantage of Trade Power buildings over Tax/Production Efficiency buildings is that provincial Trade Power is affected by only half of province autonomy, while Tax/Production incomes are affected by 100% of it. In provinces with high autonomies, the utilities of Tax/Production Efficiency buildings diminish more than those of Trade Power buildings. This advantage becomes more pronounced as your empire expands because provinces with full cores and low autonomies are relatively scarce in large empires.
  
• Trade in EU4 is an intricate system that can be fun and rewarding once you get to know it. But there are too many errors!! PARADOX FIT IT!!

Links to the rest of my guides: EU4 Advanced Economics
1. Province development
2. Buildings Part I
3. Buildings Part II
4. Manufactories
5. Light Ships