Any idea of the intermediate population between MSP and SPK on the EB? Unless there's more than I think,
The area has disproportionately high ridership compared to population. This is probably because(1) there are no expressways, no Interstates
(2) airfare is astronomically expensive
(3) the roads have a tendency to shut down in the winter
(4) no bus service
Really, look at it; the towns on the EB route have much higher ridership than you'd expect for their size.
This is why it consistently does better financially than the Sunset Limited, Southwest Chief, California Zephyr, and usually better than the Texas Eagle and Coast Starlight. It seems to be breaking even before overhead at the moment (though it'll go back into loss this year with BNSF getting OTP bonuses again).
So yes, it is serving more people. Financially speaking, if you keep only one Chicago-West Coast train, it's the one to keep.
If I-84 had never been constructed, the Pioneer would probably have been as successful; but I-84 *was* constructed. So the Empire Builder was always far more successful than the Pioneer.
P.S. This is one reason Vermont's "Western Route" will be very successful: no interstate highway competition.