The speculative trade in CT is not a comprehensive trade model by any means. But it can serve as a reality check as to baseline supply/demand coupled with how well they travel, and multipliers for ranges of potential prices.The GURPS Far Trader has rules for how far things can go and still make money. Though it is a big-ship universe, and the mechanics are different, there is still value in looking at that model as well I believe.
Essentially each system has a World Trade Number based TL, population, port type and trade classifications. Then between systems there is a BTN, Bilateral Trade Number based on distance, both sets of trade classifications. That number determines the amount of trade between any two systems. Years ago, I actually wrote software to do all that (my first Traveller trade program 20+ years ago, and the reason I started my blog honestly. I was laid off, and I had time on my hands).
Some examples of the BTN:
I personally think the distance modifier needs to be larger than it is, but the underpinnings of GURPS is a bit different than Classic.
- BTN 1: 10-50CR/year. no cargo at at
- BTN 5: 100-500KCr/year, 10-50 tons/year,
- BTN 10: 10-50GCr (billions of credits)/year, 1-5 million tons/year, 50-100K tons/week, 1-5 thousand tons a day
I tend to divide the volumes of trade (and that includes passengers) by 10 as I prefer a small-ship universe, and the GURPS Traveller universe is a lot busier than Classic seems to be.
edit: I think this is the large, commercial scale trade, not the tramp trading.
Actual demand, or a pop 4 planet would barely consume a free trader cargo and and be sated with depressed prices whereas on a pop 9 world it shouldn’t move the needle except with a full treasure fleet modeled. But it can be used to get a sense of flavor for what cargo actually moves across subsectors and what conflicts may lie beneath the surface of trade.
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