According to the the Pew Reseach Center undocumented immigration is down since mid-decade. (see above)
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, according to new estimates by the Pew Hispanic Center, a project of the Pew Research Center.
This sharp decline has contributed to 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, according to the estimates. The decrease represents the first significant reversal in the growth of this population over the past two decades.1
The Pew Hispanic Center’s analysis also finds that the most marked decline in the population of unauthorized immigrants has been among those who come from Latin American countries other than Mexico. From 2007 to 2009, the size of this group from the Caribbean, Central America and South America decreased 22%.
By contrast, the Mexican unauthorized population (which accounts for about 60% of all unauthorized immigrants) peaked in 2007 at 7 million and has since leveled off. The number of unauthorized immigrants from the rest of the world did not change.
Even though the size of the Mexican unauthorized population living in the United States has not changed significantly since 2007, the inflows from that country have fallen off sharply in recent years
What is the cause? Better border enforcement? The economy? Random?