The number of illegal Mexican immigrants living in America has dropped for the first time since the Great Depression.
According to the Pew Hispanic Center, the biggest reason for the shift is the tough U.S. economy. Pew researchers found that immigrants can't find work here, so they return to Mexico.
Approximately 6.1 million unauthorized Mexican immigrants were living in the United States last year, down from a peak of nearly 7 million in 2007.
Other factors in the shift include a decline in Mexican birthrates, tightened border controls, and a rise in deportations.
"The bottom line is that immigration is not the weather. It is something that ... can be changed," Steve A. Camarota, director of research at the Center for Immigration Studies, said.
"The economy is worse but enforcement is also higher, making it more difficult for immigrants to get jobs in states like Arizona," he explained. "They are now making new calculations and changing their views."