I certainly agree with Charles Kenny's national greatness case for more immigration to the United States. Indeed, I've written something similar in the past and recently made the case for auctioning residency permits as a way to get there. But I did want to quibble with one thing Kenny writes because it's a slight error I've seen other people make and it winds up understating the strength of his case:
If the United States can't keep up its output lead by more rapid growth of GDP per capita, then perhaps it should just find some more capita. After all, if you double the population while keeping incomes constant, you've doubled the size of GDP. And rough measures suggest that a lot of people would be willing to help -- approximately 145 million adults worldwide are keen to move to the United States, according to Gallup's global polling.
What that Gallup polling actually says is that of those people who say they want to permanently relocate to another country, 145 million of them say the United States is their first choice of second home. But another 43 million say they'd like to go to the UK, 43 million more say they'd like to go to Canada, 26 million say Australia, and 6 million say New Zealand. I can't prove it, but common sense illustrates that some of the 100 million people who prefer to migrate to some other Anglophone country would accept the United States as a second choice if we made it possible. That's not to say we should necessarily look to double our population through migration over the short term. But it's to emphasize that if we were to create more paths to coming here beyond "sneak across the border from Mexico" that the pool of people who might be interested is truly gigantic. Lots of people with no desire to permanently relocate here, for example, might be interested in a 5-year work permit.