Best place to see this is on a new beta site, which is where I noticed it, so...
Go to PETS.stackexchange.com
Navigate to the Users page and sort by ALL. Note any or all users.
Now sort by YEAR.
Notice how everyone has a 1 point of reputation difference between the two sorts?
Seems like an odd bug to me. I searched on meta and found a few about reputation discrepancies, but nothing specific to the users page.