Here's all 16 of them and all are end-to-end.
LSL(NYP) 35.1 CARD 29.4 CS 26.9 EB(SEA) 20.0
CL 34.6 SM 29.4 SWC 23.6 CZ 19.9
LSL(BOS) 33.3 CRES 28.9 SS 22.3 EB(PDX) 19.6
AT 30.3 CONO 28.4 SL 21.5 TE 19.6
Totally, totally unsurprising. This is very close to what I would have guessed. Notice that it really clusters into groups:-- LSL and CL at the top (viable Chicago-NEC trains)
-- AT, Card, SM, Crescent, CONO, CS (Other Eastern + Coast Starlight)
-- SS, SL, SWC, EB, CZ, TE (Transcons + Silver Star)
From Nate's list we know what's not a viable Chicago-NEC train.
In reality, there is much higher population density east of the Mississippi as opposed to west. The top two most populous states (
as of 2016) are California and Texas. The next ten (#3-#12) are all east of the Mississippi. Fifteen of the top twenty most populous states are east of the Mississippi and one of the other five, Missouri, is right over the river. While the SWC serves two big endpoint cities there are few major cities in between (KC and Albuquerque). So the overall demand of most of the eastern trains is higher (also the Viewliners I believe have less seating than the Superliners).
Very consistently. There's a mysterious subsidy to people who are travelling further, and it's very large -- dunno why. Penalizes stopovers.
It's better for Amtrak to have the seat filled the entire route. If someone buys a ticket on the EB between SEA-SPK and another buys a ticket between MSP-CHI, they have to sell a ticket between SPK-MSP (or a bunch of off and on tickets) or the train is empty between the two cities. A passenger between SEA-CHI fills that seat the entire route. The ideal situation would be if there were a convenient half way point between the two endpoints. Let's say A and B are the endpoints and M is that midpoint. If there's a lot of passengers traveling from A to M and a lot of passengers traveling from M to B, they can fill the train pretty well. I can't think of one train though that has that obvious a midpoint (the CZ probably has many more passengers CHI-DEN than DEN-SAC-EMY and the train empties out west of DEN). ATL would seem to be a midpoint between NYP/WAS and NOL but the PRIIA said most of the traffic is from NYP/WAS and ATL as opposed to ATL-NOL (that's why Amtrak wanted to cut cars off at ATL and actually add a coach car to the Crescent for the eastern part).