A study published this week by the Pew Hispanic Center found that over the last five years, immigration from Mexico to the United States has dropped to its lowest level in decades, hitting the key "net zero" benchmark just recently, where more Mexicans are moving out of the U.S. than there are coming in.

The study's most startling finding: while the population of legal Mexican immigrants is growing faster than it has in many years, the undocumented population is shrinking even faster. There were a total of 6.1 million undocumented Mexican immigrants living in the U.S. in 2011, compared to nearly 7 million in 2007 -- a statistic that, according to Pew, represents the first significant decrease in illegal immigration in nearly two decades.

That's happened thanks to the interactions of economic "push-pull factors," Clarissa Martinez-De-Castro, director of immigration and national campaigns for the National Council of La Raza, explained to Raw Story on Tuesday.

"In many ways, this is not surprising," she said. "Because we all know the biggest pull factor attracting immigrants into our country is job opportunity, so it goes without saying that as the economic crisis has hit our country and those opportunities are less present, it's going to have an impact on immigrants coming in. In the case of Mexico, if you combine that also with a change in one of the push factors -- that is, the growing demographics [in Mexico] -- then you have these two factors combining to lower migration."

Castro added that the "pull factor" of job opportunity may return if the economy comes back strong, which could again accelerate the illegal immigration problem, leaving policy-makers with the clear choice of preparing for that eventuality, or sticking with business as usual.

"Right now we have this space to really grapple with the state of our immigration system and how then you strengthen the legal channels for migration so when our economy bounces back, and those pull forces come again in force, that we have a system that is able to respond with legal channels that people go through, rather than around," she said.

Her analysis is largely supported by the Pew Hispanic Center's study, which pointed to the same combination of economic factors in Mexico and the U.S., along with increased border security, tougher immigration enforcement and the Obama administration's increased use of deportations as causes contributing to the reversing trend.

Pew also found that the number of Mexicans being apprehended attempting to cross the border has dropped more than 70 percent since 2005, indicating that fewer undocumented immigrants are attempting to make that passage.

"I think it's really well known that many immigrants risk their lives to come here for the opportunity of a job," Castro said. "But these state laws that make life unbearable for these immigrants, the conditions in those states pale in comparison to what [immigrants] have to endure to get here. So, that's why I think that fewer job opportunities and decreased pressure in their country of origin play a much larger role [in reducing illegal immigration]."

The study was created by combining multiple data sets from the U.S. and Mexican governments and private entities.

Photo: Stephen C. Webster, all rights reserved.