It seems to me that, in a manner somewhat evocative of the Incredible Hulk, politicians in both America and the United Kingdom suddenly mutate from passably normal humans into furious and destructive ogres whenever they discuss the matter of immigration.

In contrast, I see the issue as quite straightforward: immigration policy must be crafted in order to serve a nation's economic interests. This means that countries should try to retain or attract only those foreigners who are educated, innovative, and hard working. These are precisely the people who will enhance their adopted nation's material prosperity and cultural prestige. And these are precisely the individuals who will have no trouble assimilating into their new communities.

Foreign graduates from prestigious universities comprise one group that clearly meets these high standards. Not only do foreign graduates have an obvious potential to contribute economically and culturally, they also typically have a wide network of native acquaintances who can facilitate their assimilation after leaving university. Countries thus have a strong incentive to encourage highly skilled immigrant students to remain after graduation.

Nothing I just wrote should be particularly controversial or emotionally distressing. Yet policymakers in the US and the UK continue to behave as though it were.

The United States has a long tradition of shutting the door in the faces of foreign students, forcing many of its most talented graduates from Harvard, Stanford, and MIT to bolt back to their home countries. Even worse, by refusing to pass the DREAM Act, the US government continues to deny a future in America to some of its own residents who attend top universities, simply because they were brought to the country illegally as young children.

Britain, more reasonably, currently issues post-study work visas, which allow foreign graduates to live and work in the UK for two years after obtaining their degrees. But the Cameron government formally announced last week that post-study work visas will no longer be issued from 6 April of this year. Thousands of talented foreign students, as a result, will return to their home countries rather than remaining in the UK after graduating this summer. (Here I must admit my personal interest: as a US citizen studying in the UK, I would have applied for this visa had it not been eliminated.)

To replace the post-study work programme, the UK government has announced that it will allow a limited number of foreign students to remain in the country as 'Graduate Entrepreneurs.' But this is a poor substitute. First, the application process is excessively complicated in comparison to the current rules, which will deter many students from even trying to apply. Second, it discounts the economic and cultural contributions foreign students can make even if they are not prepared to become entrepreneurs straight away. And third, the new rules aren't particularly appealing even to students who do want to start a company: the government will require that applicants for a graduate entrepreneur visa receive approval by their university for their business idea (as though a university could somehow predict which potential businesses will succeed)- which necessarily involves students divulging secret and sensitive plans to unknown outsiders.

The inevitable result is that the UK will begin to emulate one of America's worst mistakes by preventing talented graduates from remaining in the country. Even worse, the end of the post-study work regime will discourage talented students abroad from even applying to study in Britain in the first place, diminishing university revenue. And this isn't just hypothetical: Australia recently announced that it will instate a post-study work visa because the number of foreign students applying to Australian universities fell so precipitously after restrictions on student visas similar to those the UK has just passed were announced a few years ago.

It's doubly frustrating to know that the Cameron government has made this decision largely because it is shackled to the foolish European Union immigration laws that force the UK to admit tens of thousands of unskilled workers from Europe every year. And as long as the government is unwilling to disobey Brussels, the only way left to reduce net immigration is to further tighten the vice on the inflow of non-Europeans, even highly skilled ones.

So to politicians on both sides of the Atlantic, I conclude: chasing foreign students out of the country after they graduate is not good policy. It is economic self-immolation. It deprives Britain and America of the invaluable advances in culture and technology that will now be made in India, China, and Brazil instead. And it guarantees that 'The West' will continue to lose global influence as the heart of the world economy moves elsewhere.