Each CoT has a trade value, in ducats, which is the sum of the generated trade in all provinces which are part of the CoT's trading area. The trade value of the CoT is shown on the center of trade screen, and also on the main map when it is in trading map mode. Although trading income is computed monthly, the displayed trade value is a sort-of yearly figure. The monthly amount of trade is the displayed figure divided by 12.
The trade value of each CoT is divided into twenty shares, which are paid monthly to countries with merchants present in the CoT. Each merchant takes one "slot". Each slot controlled by a country gets it one share. Thus, country with five merchants gets 1/4 (5/20) of the total trading income. A country with 6 merchants has the monopoly in that CoT, and gets six shares for the six slots it controls, plus the shares for all empty slots. If no country has a monopoly, then nobody gets the income for any empty slots.
Thus, here is a formula for the trading income for country X from a CoT Y:
- trading_income(X,Y) = trade_efficiency(X) * #shares(X,Y) * net_generated_trade(Y) / 240