Yeah, that's why I framed my comment as a question - looking back I realize it comes across a little passive-aggressively, which was not my intent! Sorry if the comment seemed shady.

I did some cursory digging and am having trouble defining "ridership" in this case - it would change things a lot if "ridership" is total rides taken (what you went with) vs total riders using the service.

I'm not a huge Amtrak user but I've taken the Empire builder line a few times over the past 5-10 years and did have to book my ticket with ID (similar to the process for booking an airline ticket), so theoretically they COULD deduplicate total riders rather than just total individual rides taken.

But on the other hand, total individual rides taken would be a bigger number, and if Amtrak wants to brag on the usefulness of their service they'd want to highlight that. So...yeah, you're probably right. I can't think of a reason they'd HAVE the total number of rides taken and NOT publish it, instead opting to go with the smaller number of total people using the service. Occam's razor, marketers pulling together public-facing reports are gonna be marketers, etc.

tl;dr on second thought, I agree with you and retract my speculation!