Different_take_on_immigration

Third, and most interestingly, Bohanon and Van Cott argue convincingly that the open-immigration policy America followed during these years effectively undercut tariff protection. After all, if people can come freely to the U.S. – as they did, in droves, during this time – the notion that growth depends upon protecting American workers from foreign workers is undercut.
http://cafehayek.com/2005/04/immigrants_and_-2.html