BRYAN CAPLAN: With so many foreigners wanting to come to America, why would an American ever marry an American? He has answers. Plus this: “When I ask, ‘Why do Americans ever marry Americans?,’ I suspect that many non-economists will object, ‘What if everyone thought that way?’ An intriguing hypothetical. If 50% of Americans started marrying foreigners, I suspect that nationalists would soon tighten restrictions on marriage visas. If 90% of the 50% of Americans marrying foreigners were male, I suspect that domestic feminists would join forces with nationalists to ‘ensure fairness to women.'”