Net undocumented immigration is now zero:

Number Of Undocumented Immigrants From Mexico Who Are Entering and Leaving U.S. Hits Net Zero, by Amanda Peterson Beadle, ThinkProgress: According to Mexican census data, 1 million undocumented immigrants returned to Mexico from the U.S. between 2005 and 2010 — more than three times the number who said they had returned from 2000 to 2004. The majority of these immigrants are returning to their homes for good, leading to a massive shift in Mexico, which has relied on billions in remittances as a form of social welfare. And the changing immigration patterns has led to “net zero” migration:

At the macroeconomic level, Douglas Massey, founder of the Mexican Migration Project at Princeton University, has documented what he calls “net zero” migration. The population of undocumented immigrants in the US fell from 12 million to approximately 11 million during the height of the financial crisis (2008-09), he says. And since then, Mexicans without documents aren’t migrating at rates to replace the loss, creating a net zero balance for the first time in 50 years.

...The shift began as a result of the weak U.S. economy, but experts say anti-immigrant state laws, tougher U.S. border enforcement, and border violence are contributing factors as well.