1. “The annual inflow of unauthorized immigrants to the United States was nearly two-thirds smaller in the March 2007 to March 2009 period than it had been from March 2000 to March 2005…”
2. There has been “an overall reduction of 8% in the number of unauthorized immigrants currently living in the U.S.-to 11.1 million in March 2009 from a peak of 12 million in March 2007…”

How can we try to explain these changes? I gave my take to KUHF but in a nut-shell there are two compelling reasons:

1. The economic crisis: Fewer jobs for migrants -”the unemployment rate for migrant workers without documents of all ages in March 09 was higher than that of U.S. born workers or legal immigrants 10.4%, 9.2% and 9.1%”. Migrants tend to be overrepresented in those industries that have taken a solid hit by the crisis (construction and services).
2. The border is more secure: Crossing the border has become much more expensive not only in economic terms but also it entails risking your life by crossing through the dessert and/or being abandoned by a “coyote” 

The result: The cost of crossing (in the short run) outweigh the potential benefits of migrating especially given that the likelyhood of finding a job is not so good.