Okay. I have lots of threads on this forum about world building for economics, so I fully understand that. I just feel that using the player facing speculation rules (including TCs) is a very rickety scaffold on which to build, because it doesn't address 90% of the economic activity (ie what's done by real mercantile companies).
I get that it is the only "mechanic" that we have. Just keep in mind you are trying to build Call of Duty with only rules for how pistols work. I also strongly feel that the way trade would look in the Trojan Reaches is rather different than it would look in the Spinward Marches and be hardly recognizable compared to trade in the Core because of the differing volumes and levels of organizations.
I agree with a lot of this, but the speculation rules are not used by the big boys. (not much anyhow) The reason for this is the limits placed on how much spec cargo ports are willing to buy at a time. I use the same rule for how much is available to buy for how much is available to sell as well. The big boys primarily rely on shipping other people's goods for a flat rate. Now this rate should be different for each ship, because the running costs versus cargo capacity are different from ship to ship. Currently the rules do not cover this. Myself or Geir could probably write a simple mechanic that does this, but currently it does not exist. Just this little rule change would vastly improve the Trade System in Traveller.
Add up your operating expenses for 1 week in jumpspace and one week in normal space. Divide that by a % of your cargo capacity (80 or 90% or so.) times the cost per jump. In Traveller, it is 1,000Cr per ton per jump 1. This would give you a new price for shipping a ton of cargo, one jump. This allows for the granularity, while still keeping things simple. This calculation is done once per ship, prior to it's construction and does not change unless the ship is refitted changing its characteristics. Simple. Easy. Flexible for players and Referees alike.
That is how you can use the Trade Rules to show how it works for the big boys as well as the tramp traders. Again simple. Easy. No extra rules for the big boys that don't apply to the tramps. All rules apply to everyone. Big boys just get the advantage of scale. (and negotiated tax breaks and such, but taxes and such aren't in the rules.) This would cover trade in the Marches as well as in Core. The only things that would change would be the ships carrying the cargo and the size of the ports of call.
Once you have this information, you can figure out a general idea of how trade flows at the Micro-scale as well as at the Macro-scale. Then you can figure out all of the different things both positive and negative which may effect these numbers, such as a war, Amber and Red Zones, Trade Treaties between governments, etc. This will allow you to do everything that you wish while still keeping the rules Player-facing.
I'm not you and I'm not going to tell you what will work for you. But when i world built the trade for my campaign, I basically ignored the trade codes because I don't feel like they tell me much of anything. What does Non Industrial tell me that the low pop value doesn't? Nothing. Does every pop 5 world need the exact same things? I don't think so.
I feel like the facts that matter for traveller trade are: 1) Jump 1 & 2 are significantly more profitable than 3+. 2) Jump prevents super tight scheduling or knowing the best prices between two similar worlds 3) The more a regular freighter with a full crew jumps, the more profitable it is. 4) Basically any amount of in system travel is cheaper than micro jumping (unless you use the 1000D limit), so commercial jump ships won't be making interplanetary runs.
In my campaign, I don't have ships above 600 dtons that land on planets. 1 to 5k dton ships are the most efficient (my campaign is not inside the Imperium, so I don't believe that those massive megafreighters would make sense or be affordable), but they require some way to get the cargo to the surface if there is no high port.
So I wrote a few paragraph sketch of what each world was like. That way I knew what was important to each world. What its port rating meant. What does it produce that other worlds desire, what does it import in particular? What distinguishes *this* world from every other Industrial TC world in the region? How different are they than the High Pop worlds that are classed as "pre-Rich" instead of Industrial solely because you can breath their atmospheres without assistance? Does any world have unique trade goods? Is that the only world in the region to produce natural zuchai crystals? Anagathics? Psi drugs? Are their fresh fruits shipped in giant low berths? Is this world Amish and just not want your industrial products, period?
I love this part here! It is not covered by the Trade Rules as it is too granular for rules in general, but I could see having a Trade Good, like Zuchai Crystals, or natural anagathics could give the world a +1 to their Importance Code, which would increase the amount of trade in a system over what the UWP would indicate. It would also likely lead to an increase in port size.
Are there any worlds with F type stars where the star's 100D limit might be farther out than the planet's? If there is a long run in from the star's 100D limit to the mainworld, that's gonna distort trade to that world. Conversely, is the main world some asteroid that you can practically arrive on top of?
Did Geir write an Efficiency Rule into his WBH? If so, lower or raise the efficiency due to Jump Shadow or lack thereof and call it done.
Then I looked at what are the J1 or J2 routes between the big high pop planets? I explain why any worlds on that route have substandard facilities. Or just flat out put space stations for refueling away from the planet and say the crap rating is the world's immediate environs. And make those facilities private, requiring membership in the GeDeCo fanclub or whatever. I also flagged any worlds that are starved for trade because of distance, political problems, lack of goods, etc. I never really found any value in giving ratings to the feeder routes. Anywhere that isn't "main trade route" or "what's trade?" is like whatever, unless it is a hub for your campaign.
Macro-scale trade route building is a pain in the ass currently. I love having them, but I hate building them. It is very time intensive to calculate every BTN for each world within 6 Jumps for J-1, J-2, and J-3 jump routes. That has to be done for each system individually, then you have to overlay all of the trade routes to see which overlap. If you have 3 routes of the same type moving along the same route between two worlds, increase to the next higher BTN to get the rough trade volume between routes of one jump in length, 1, 2, and 3. 4 as well, if it is on an X-boat route. (These rules came from GURPS Far Trader btw. So you know where I got them. lol.) A computer program could literally do all of this for Us in minutes, but I am not aware of one that exists for this purpose.
I use the jump accuracy that's in the companion or JTAS article (forget which). So the majority of ships coming to a given world arrive in roughly the same box of space. Ships *can* arrive somewhere else, but commercial ships aren't going to because that'll cost money and/or increase risk.
In the Reaches, you may have worlds just no one goes to and they are struggling to get needed supplies. In a more civilized region like the Marches, they'd probably have at least a subsidized merchant bringing necessities, if not a full fledged minor company or group of companies.
This all makes good sense to Me as well.
Once I've made the worlds in my play area unique and figured out the general flow of trade, I figure out who is actually carrying that trade. Government ships? Specific merchant companies? Subsidized merchants? What are the merchant companies and what are the typical ships? Do ships run around solo or do convoys happen? How much trade collusion is there? Are there weak links on the trade route that might work for piracy? How do merchants deal with that?
You may have a different experience, but I found no value in the player trade mechanics for purposes of this world building. So I didn't worry about it. How Jump works is the main mechanic that actually affects things, imho.
The reason you cannot find any value in the Trade Rules for worldbuilding is the writers stopped the description at the Micro-scale, but made all of the trade activity based on the Macro-scale. That is why I said in another post that the Trade Codes need to be changed to be more understandable and simpler, while being able to apply to both micro and macro scaled trade.
Everything you have done with figuring out who is carrying the cargo, what merchant companies are operating, typical ships sizes, solo or convoy, subbies or tramp traders, trade agreements, anti-pirate patrols, etc. This is all doable, because you already know the information that I am trying to generate. The only difference is that you are just creative writing. You are using no rules to do so. I do creative writing too for worldbuilding. The only difference that I create the framework with the rules, and then add the fluff details afterwards. I am not talking about table for random creation. I hate those. lol.
I don't know if the main mechanic of importance is jump, but it is definitely up there.
I wrote something up for that and I THINK I sent it in to Freelance Traveller (I know I got some great feedback from JeffZ on it).
