Going back to the original topic, I tend to look at the system and make some generalizations based on what I know about it.
For example if a world has a hi population over 10 billion it likely cannot produce enough food to support its population, so its a good candidate for importing both food from other worlds as well as fertilizer (rock phosphate) to supplement its agriculture. That same world is also likely to have a strong industrial base and will need to import raw materials (i.e. metals) from elsewhere if its depleted its own system (including those found in asteroids, small moons, etc. possible in a long established world). It will in turn need to export finished products to offset these imports and maintain its economy. That's a lot of bulk in and bulk out.
Nearby medium pop worlds might be distribution points. Ore haulers from outer systems bring raw materials there where they are warehoused until there's enough to fill a large bulk freighter (the big 200,000dT ships). Likewise finished goods are dropped off there and sent out on smaller 2000 dT or smaller ships to the smaller worlds.
Small pop worlds likely import most things they need because they lack the industrial base to produce enough on their own. In exchange they need to produce something for export, again to maintain their economy, unless they're a subsidized colony (meaning someone else is paying the tab). Small worlds might focus on high value, small cargoes like precious metals and minerals, radioactives, high value biologicals (luxury food items, rare herbs or other plants, rare animals or animal products). Such smaller high value cargoes are easier to produce with limited manpower and have high enough value to cover the cost of everything they have to import.
How the trade lanes are arranged will also affect things. A world at the hub of several trade lanes is a natural distribution point regardless of its population or industrial base. If it is a medium or high pop world, then its likely going to be a very busy place with a lot of ships coming and going, large freighters, smaller freighters, passenger liners, private ships, etc. Perfect place for organized crime and smugglers to set up as all the traffic gives them cover for their moment (get lost in the crowd, hide in plain sight) and all that cargo coming and going... who's going to miss a bit lost do to "transit damage" or just a misdirected warehouse manifest.
Just some thoughts.
). Sounds VERY familiar!
