35% of a million students in the USA is very different to 35% of a billion students across the USA, Europe and Africa. Since there aren't a billion students in

35% of a million students in the USA is very different to 35% of a billion students across the USA, Europe and Africa. Since there aren't a billion students in the USA, 35% of them is an impossibility. If you scale your population above some recognized boundary you aren't sampling in the same space any more. After all the local star density to 1AU tends very strongly to 1. That's not indicative of the actual star density in the milky way.