Sense from Matt Yglesias:
According to Gallup there are 150 million people around the world who say they'd like to move permanently to the United States. Right now the United States has about 89 residents per square mile. Add another 150 million people and we'd be at around 135 people per square mile. How would that stack up in context? Well, France has 303 people per square mile and Germany has 593. Japan has 873. The Dutch have 1,287!
All those places have their share of problems (and so do we) but none of them are exactly post-apocalyptic hellscapes.The equivalent Gallup number of people who say they'd like to move permanently to the UK is 45 million. That would take us from the already relatively dense 673 people per square mile to 1,153 people per square mile, edging out Rwanda, but still not quite as dense as the Netherlands or South Korea. I think we'd manage. Personally, I also think British people are great, and it would be great to have more of us.