No shit, logic also dictates than when a country is being established from nothing, that the percentage of immigrants will be higher than in subsequent times when a nation of over 300 million people has already been established, for over 2 centuries now. Pretty much every single nation in existence was once the result of some immigrant group emigrating somewhere.
Australia in the 1800's also boasted a higher number of immigrants than it does today, that doesn't mean that they need to be hauling in millions today. The necessity for such excess amounts of man-power, no longer exists.
Some people brought up the lack of immigration in the mid-20th century America, almost as if it was a bad thing, some sort of a racist machination preventing America from coming to "full bloom". Yet all things considered, America seemed to do pretty fine for itself during that time. Fine enough to become the most powerful country in the world.
