I think what we're saying is there are really big ships doing the bulk of trade among major worlds with smaller ones filling in the holes. [...]
I guess the biggest influence for my take is SMC and Al Morai. [...]
As for robject's note, I suspected it was from conversations with Marc.
Looks like I'm working basically from the same notes as you, Dan. And I know Hans has different notes.
And, please note that Hans and I had a long discussion about Al Morai on COTI a couple years ago.
http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=1120&highlight=al+morai
One important conclusion I reached through talking it out was that:
economics [of companies like Al Morai] aren't the same as those used for players in a tramp trader... I suspect that [an] implied, undocumented economy exists only along the Xboat route. It's too powerful otherwise.
...
We all know this, because the XBoat transports can haul 600-1200+ tons of cargo. We can also infer this from the fact that a fleet of Jump-4 vessels running along the XBoat route can turn a profit.
The 100,000 ton freighter is such a bizarre mention, too.
Here's what Marc thinks, on those rare occasions he thinks of interstellar traffic. It agrees with my preferences, and it gives me an upperbound on how many large companies may be operating in the marches... or anywhere.
What benchmark do I want to see?
a sleepy backwater starport has 1-10 starship departures/ arrivals per week.
a bustling on the route powerhouse starport has 1000 departures per week. I bet they have an orbital starport and shuttles carrying people to Orbital rather than crowd 1000 ships on the ground.
Add to "Departures" the ancillary stuff... free traders, scouts, yachts, which are basically inconsequential and are more likely the same numbers at ANY world.
"1000 departures per week" means (I think) roughly 6 significant* ships arriving and 6 significant* ships leaving each hour, every hour. One ship arriving and one ship departing every 10 minutes.
Low traffic.
Assuming "Significant" means something like regular, scheduled, corporate traffic, then a picture can be drawn, and various estimates made. Whipsnade argues reasonably well for the Marches having three sector-wide lines, Al Morai being one of them (HQ in Mora), and another headquartered at Glisten. Perhaps the third at Trin, or Lunion. Add in megacorp subsidiary lines (Akerut, plus one for Naasirka based out of Rhylanor, etc). Beyond that, we have interface lines (Oberlindes, McClellan, Baraccai Technum) and subsector lines (Sinzarmes).