So. What lesson can we extract from this little dance? ...
Mostly that it's hard to resist a good waltz, I think, and it can be fun to watch. That, and that accidentally stepping on someone's toe is an occasional and unavoidable hazard of the dance.
At least it is for me. I seem to have two left feet in such things.
Now as I recall, before the music changed, the song was, "How to address the problem of the numbers," which was sung to the tune of, "Just how many ships are out here anyway?"
As I said, GURPS offers some data, but it does not apply easily outside of GURPS since their trade picture is a little different: they aren't faced with the Cr1000/dTon cap on cargo fees regardless of jump range. There are also some other little differences that may play a role, and I recall other issues coming up the last time they came up. Still it might give us a ballpark to work with, which we don't now have.
There are four dark blue "major" routes, I think 56 aqua "main" routes, about 260 green "intermediate" routes, about as many yellow "feeder" routes (they're hard to see), and about 173 red "minor" routes. (I might be off by a couple here or there.) Makes it roughly 50 to 100 million dTons weekly traffic. Seems like a lot. Les'see, estimated Marches pop around 375 billion - about 1 dTon per 4,000 to 8,000 pop per week. Someone else can figure if that's in the right neighborhood or way off - we can always scale from that estimate if needed.
http://wiki.travellerrpg.com/File:Spinward_Marches_Sector.pdf
Description in the Wiki (
http://wiki.travellerrpg.com/Trade_map_key) says:
Red/minor route: served by between four and eight small liners
(probably Type M Subsidized Liner or Type R Subsidized Merchant, or similar) and an equal number of free traders, with a general average of one ship per day entering or leaving each port. So, roughly 14 ships on these routes, about half free traders (or far traders) and about half the 400-600 dT ships. Note that I figure this route as having a bit more than twice the capacity needed: ships are averaging less than 50% full, so this is a route that needs subsidies or clever captains who know how to buy and sell to survive. Or, maybe there are fewer ships. Passenger service is negligible. 173 such routes: about 1200 free traders, as many 4-600 d-Tonners.
Yellow/feeder route: between four and eight larger freighters, with an equal number of smaller liners and free traders, with two to four ship per day leaving or entering port. So, roughly 28 to 56 ships on these routes with about 14-28 large freighters, 7-14-ish free traders (or far traders), 7-14-ish 400-600 dT ships. If we assume the large freighters prefer to run full and go with the lower quantity, I'm guessing they're 2-3000 dT. ~260 such routes: about 1800 free traders, as many 4-600 dTonners, about 3600 freighters in the 2-3000-ish ton range
Green/intermediate routes: "served by twenty to forty large freighters and a smaller number
(not specified) of liners and free traders." "On average ten ships per day enter or leave port", so about 140 ships regularly serving this route, which is not adding up to "twenty to forty ... and a smaller number". I'm guessing ~30-40 free traders, ~30-40 400-600 tonners, maybe 70-ish large freighters. We could fiddle with that depending on the size of the freighters but then the ten-per-day goes by the wayside. We also have a problem: five times the shipping serving ten times the cargo. We can assume the large freighters are 4-6000 dT, but that means they're either different from the feeder freighters or the feeders run at half capacity. Probably best figure a range of everything from 2-10,000 or more, averaging about 5000. ~260 such routes: about 9000 free traders, as many 4-600 dTonners, about 18,000 freighters in the 2-10,000-ish ton range.
Aqua/main routes: served by "the very large mega-freighters," with "dozens of smaller freighters and liners." "There may be as many as 20 ships per day entering or leaving port," so about 280 ships regularly serving the route. We could double the Green numbers and still have 80% of the traffic served in "mega-freighters," which I'm going to guess are in the 200,000 dTon range - problem is we need about 14, and I would have expected some in an intermediary size class; of course, we can play with it a bit. Anyway, ~56 such routes: about 4000 free traders, as many 4-600 dTonners, about 8,000 freighters in the 2-10,000-ish ton range, about 800 megafreighters.
Blue/major routes: "A dozen mega-freighters and as many as 100 smaller ships regularly travel this route. There can be as many as 50 ships per day entering or leaving port." About 700 ships regularly serving the route. Again, a problem: three times the shipping serving ten times the cargo, but perhaps we're dealing with larger superfreighters, averaging closer to 500,000 dTons. I'll take the Aqua numbers and pop them up by 2.5, and assume larger superfreighters account for the added tonnage: ~150-200 free traders, ~150-200 400-600 tonners, maybe 3-400 large freighters, maybe 40-ish superfreighters. 4 such routes: about 700 free traders, as many 4-600 dTonners, about 1400 freighters in the 2-10,000-ish ton range, about 160 megafreighters. We make the assumption here that a route shipping 5 to 10 million dTons of cargo weekly has a fraction of a percent in the kind of trade that needs the services of a free trader or other small freighter.
So for the GURPS Marches, and with a lot of assumptions, we're guessing around 16,000-17,000 free traders, maybe as many 4-600 dTonners, about 31,000 large freighters of from 2000 dTons to maybe 10,000 dTons, and a bit less than a thousand megafreighters. Big numbers, but it seems to be where GURPS leans and might explain why the IN feels its worth putting several hundred capital ships in the sector.