Not sure there's enough data to prove or disprove what you're doing with the math. But if you only have records since you've been here, that makes sense. It's not quite what I'm looking at for the portal yet, but it'll be interesting to see how this changes with more to go on.
Maybe you could see if anyone who were in previous non-native universes have data from them. That could be useful (a whole other sort of variables, but ¯\_(ツ)_/¯ ).