From the screenshot it looks like you can steer trade directly to Sevilla all the way from Indo-China across Africa but I don't have many provinces in Indus so I can't push it to Zanzibar efficiently. I try not to go over 100 overextension.
The intention of my thread was not to measure who has bigger trade income but to argue whether
a) special trade buildings worth it
b) CNs don't give much trade due to low production, hence they are useless
c) AI doesn't usually build buildings so their economy cannot afford large armies/mercs, hence weak competitor
I actually agree with you that one must build production buildings to compensate low initial trade value because without it... well, total trade value in Caribbean is 20, 9 in Mississippi and 10 in Chesapeake, 5 in Siam, 9 in Canton which is less than satisfactory.
How did you manage to crank up tariff income to 50 ducats though?