Exact bonuses to Trade from Buildings?

[Slaists]

On land: paved highways give the main boost to trade (not on islands though). In the sea: the harbors. But the latter is true only if you have other harbors to trade with (harbors in provinces that lack the resources you can trade and that belong to factions that are not at war with you and optimally, that belong to factions that you have trade rights with).

If you lack the harbors to trade with (or the harbors you have trade with has less trade routes than yours), some of your trade routes will be "idle". Check in western sahara: you can build a harbor there, but there will be no sea trade in the province (at least until the ocean-going age. and i have not played to that point yet...). Markets, Print-Presses, Banks - all give considerable boosts to trade, but only if the province has significant resources to trade to start with.

Also, in v 1.02, if a general sits in a city without a basic market building, he is highly likely to earn "ignorant" and "incompetent trader" traits: these traits appear even if the first building built is a road or harbor (rather than the corn trade shack). It seems, the game wants the basic trade building to be the first to be built. Both "ignorant" and "incompetent trader" traits can hurt trade considerably. Especially in the resource rich provinces.