I think you are missing the key point that Carter says more than just that we have a 5% chance of being in the first 5%, it also tries to use the fact that we are the 10 billionth born to say that this says something about our total populations. I'm saying that you cannot use both of those numbers to generate a third one, like an "expected longevity" of humanity. That is exactly the same mistake as using $10 to get an expected value for the other envelope, by any method. You're saying you don't care about the 10 billionth-born subset, all you care about is the 1/20 of the total attendees who are in the corner. But if that were true, you would have to be able to state Carter's claims without applying it to us, because we're in that subset of 10 billion borns, and there are not 1/20 of us in the corner. Carter's error is in the number 200 billion, not in the number 5%. We are 5% likely to be in the first 5% until you use the information that we are 10 billionth born. You can't use both those numbers and apply it to us.