I've written before on this site advocating a more open stance toward immigration. Benjamin Powell, writing for the Library of Economic and Limits argues for open immigration not on moral or spiritual grounds but on economic grounds. In particular, his piece argues that those who oppose immigration on the grounds that open immigration is in fact a benefit not only to the economy overall, but in fact to native born workers too.
"Unfortunately, much of the popular debate on immigration is based on fallacies and misconceptions. Immigrants are not a drag on the economy. They don't take jobs from the native born population and they don't depress overall wage rates. Fears of immigrant crime are overblown. Finally, objections to immigration because of the welfare state or public property are misplaced.
Restrict trade and cries of protectionism resound. Suggest linking labor standards to trade and it's protectionism in disguise. Limit capital flows and the International Monetary Fund is on your back. But restrict people flows? That's just an accepted exercise of national sovereignty!
That immigrants "take our jobs" is probably the most repeated and most economically ignorant objection to immigration. It's a classic example of Bastiat's 'what is seen and what is not.' Everyone can see when an immigrant takes a job that used to be held by a native-born worker. But not everyone sees the secondary consequence of the new jobs that are created because native-born labor has been freed up for more-productive uses. In the market's process of creative destruction, jobs are created and destroyed all the time."
The full article at the Library of Economics and Liberty is available here.
If economics is your thing, you might also enjoy Bryan Caplan, author of the Myth of the Rational Voter, discussing open immigration with Russ Roberts on Econtalk here.