Something that comes up when I write about immigration is the idea that the United States is somehow running short of capacity to absorb immigrants. I see no reason to believe that this is the case. The USA historically maintained an open borders immigration policy precisely because it was such a sparsely settled place, and we abandoned that policy amidst a panic about Communism and the allegedly un-democratic values of Catholics, leaving us to continue to be a relatively sparse country.
For a window into that, I asked Matthew Cameron to whip up a fun little chart. It shows how many people the USA would contain if the entire land area of the 48 contiguous United States were as densely settled as some of our member states currently are today:
New Jersey, if you’ve been there, isn’t exactly a dystopian nightmare of overcrowding. It doesn’t even contain a major city. It’s basically a lot of old-school suburbs, plus a few small cities, with room for farms and even the infamous Jersey Shore. And yet if the whole land area of the non-Alaska, non-Hawaii United States were as dense on average as New Jersey it would hold 3.5 billion people. Obviously there are a number of practical problems with this, including the fact that only 145 million people even want to move here, but the point is simply that accommodating the people as such is not the issue. The fact that infrastructure can’t be built out instantly is a real issue, but we’ve had population growth rates 0.5–1 percentage point higher than we do now with no problem.