Freakonomics’ Mellisa Laffey interviews British economist Philippe Legrain.

Legrain has served as special adviser to the director-general of the World Trade Organization and worked as the trade and economics correspondent for the Economist. His new book, Immigrants: Your Country Needs Them, has been nominated for the Financial Times/Goldman Sachs Business Book of the Year Award.

Q: You argue that immigration is a good thing, under almost any circumstances. Why? Are there any circumstances in which it isn’t good?
A: I think freedom of movement is one of the most basic human rights, as anyone who is denied it can confirm. It is abhorrent that the rich and the educated are allowed to circulate around the world more or less freely, while the poor are not — causing, in effect, a form of global apartheid. So I think the burden of proof lies with supporters of immigration controls to justify why they think letting people move freely would have such catastrophic consequences. And, frankly, I don’t think they can.

The economic case for open borders is as compelling as the moral one. No government, except perhaps North Korea’s, would dream of trying to ban the movement of goods and services across borders; trying to ban the movement of most people who produce goods and services is equally self-defeating. When it comes to the domestic economy, politicians and policymakers are forever urging people to be more mobile, and to move to where the jobs are. But if it is a good thing for people to move from Kentucky to California in search of a better job, why is it so terrible for people to move from Mexico to the U.S. to work? …

From a global perspective, freer migration could bring huge economic gains. When workers from poor countries move to rich ones, they can make use of the advanced economies’ superior capital, technologies, and institutions, making these economies much more productive. Economists calculate that removing immigration controls could more than double the size of the world economy. Even a small relaxation of immigration controls would yield disproportionately big gains.

Read the whole thing.

Personally, I think Legrain is perfectly correct, with the exception of his ultra-libertarian perspective on Islamic immigration. I suppose it’s just the case that I believe that extremist views and hostility to the West are more common among individual Muslims than Legrain does.

Islam is not simply another religious denomination. Islam features even more intransigent claims to authority than the most authoritarian forms of Christianity extant today, and subscribing to a fundamentalist form of Islam is very likely to involve religious obligations to support violence against Western governments and/or non-Muslim inhabitants of Western countries.

Admitting Islamic immigrants at the present time would be a great deal like having an open borders policy for Germans or Japanese during WWII.