After researching astronomy, I was under the assumption that trade routes would extend over the ocean (in the tech description). However, in my standard, ring, 6 civ map, I had open borders w/ Mansa and GW, but was only trading with isabella, my next door neighbor. Why was I unable to trade overseas? Some of my cities were on the coast, but no luck. Also, does distance increase trade yield, or just if it is foreign or domestic?

I think the other city's size and whether it is foreign impact per city trade income the most.

I think the there is a complex calculation for which cities you trade with, and couldn't tell you why you're not trading with Mansa at the moment.

Doesn't it also depend on the number of trade routes allowed in each city?

The game calculates the best trade routes (highest commerce) and uses those first. So if CityA gets +3 from CityB, +3 from CityC, +2 from Mansa, +2 from GW, and +1 from GW2, then, depending on the number of trade routes allowed, it will take them in descending order. Two trade routes would mean that CityA trades with CityB and CityC, but three trade routes would add Mansa's city.

Actually Foreign trade routes yield significantly more... to get them you need a few things

1. a Trade Route (which Astronomy should allow if the Path is VISIBLE) if you have Astronomy there may still be some ocean you need to explore

2. Open Border Agreement

3. No Mercantilism.


the basics formula for trade yield is

City population factor * MINIMUM of (other city population factor and distance factor)

with multupliers for foreign trade routes and harbors