The NY Times Magazine has a long and very interesting story about immigration and economists. The two main stars are George Borjas and David Card, immigrants both (from Cuba and Canada, respectively), who have been wrassling over the economic impact of unskilled immigrants for a long time. A snippet:
Like any form of economic change, immigration causes distress and disruption to some. But America has always thrived on dynamic transformations that produce winners as well as losers. Such transformations stimulate growth. Other societies (like those in Europe) have opted for more controls, on immigration and on labor markets generally. They have more stability and more equality, but less growth and fewer jobs. Economists have highlighted these issues, but they cannot decide them.
Whole thing here.