Merchant

From EU2Wiki

Merchants are a kind of state agent that may be sent to centers of trade to attempt to secure slots there, and thus obtain a fraction of the trade value for the owning country.

Normal merchant generation happens at the start of each month: a country will either gain no merchant that month, or it will gain one. If you hover over the merchant icon at the top of the screen, you'll get a tooltip showing the yearly number of merchants your country gets, and the breakdown according to the following factors:

N	Factor	Exact value
-3 to +3	Stability	your stability
+1	Coastal Provinces	+1 if you own at least one port city on your home continent.
+1 to +3	Protestant Coastal Provinces	+0.5 for each home continent port city which is of the Protestant or Reformed religions. Maximum of +3.
+2 to -2	Domestic Policies	+2 - 0.4*mercantilism
+1 or +2	Trade Level	+1 if trade tech is 5 to 9; +2 at trade tech 10
+1/CoT	Centers of Trade	+1 per center of trade owned
+1/monopoly	Monopolies	+1 per monopoly you have

There is a maximum rate of 12 merchants/year (1 per month).

It is also possible to gain merchants via events. A few countries have scripted events which give them merchants. There is also the Rush of Merchants random event and several others that give merchants in random events.