Link:
http://online.wsj.com/article/SB124424701106590613.htmlI have no doubt that worsening economic conditions in much of the developed world has contributed mightily to this trend. But there are a couple of extra factors to consider in the U.S. context.
Much of the legal migration to the U.S. goes through the family preference system. There are very long queues in some of those categories. I doubt that current economic conditions have deterred too many of those legal migrants whose number just came up after waiting around for years.
On the other hand, a very large portion of the migration flow (at least a third) is made up of illegal immigrants. I suspect that the illegal immigrants are much more sensitive to changing economic conditions. So much of what we are seeing in U.S. trends is probably driven by illegal immigration.