No idea, trade is mostly a mystery to me. I have plans to set up a script and extract data from my trade fleets so I can graph and analyse it, but I also have a son that is almost 2 years old, so finding the time isn't easy.
At a guess the Trade fleets should calculate tariffs into the profit/loss decisions, so high tariffs might discourage fleets from visiting your worlds. It would depend on what rates and prices surrounding planets have I guess.
Is trade with foreign planets a good thing or a bad thing? Does it tend to leak cash or goods?
