As Donald Trump vows to shield America from a deluge of Mexican migrants, he may be a bit flabbergasted by this fact: More Mexicans have actually left the States than entered it in recent years.

The US saw a net decrease in Mexican residents from 2009 to 2014, a report by the Pew Hispanic Center reveals. The trend marks a major shift in migration patterns by the largest foreign population in the US. There was a net decrease of 140,000 residents in the five years to 2014, compared with a net increase of 2,270,000 from 1995 to 2000.

The overall decline was mainly in undocumented individuals, from a peak of 6.9 million in 2007 to an estimated 5.6 million in 2014. Most people went back to their home country of their own accord, with the stated purpose of reuniting with their families. A small portion, 14 percent, were deported.

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Fewer Mexicans entered the country partly because of the US recession in the early part of the period examined, while there was a boom in Mexico’s economy.

“There were a lot less jobs particularly in construction, which made people go back to Mexico but also made it less attractive to come here,” the author of the Pew report, Ana Gonzalez-Barrera, said.

Heightened border security, implemented under the Obama administration, also may have deterred people from making the journey north, Gonzalez-Barrera said: “Border security has a big impact in terms of people wanting to come here.”

According to immigration scholars, the Pew findings confirm similar research from recent years. A recent report by the Census Bureau found more Asians than Latin Americans were migrating to the US, until in 2013 China replaced Mexico as the top country sending immigrants to the United States. Other data shows illegal border crossings into the US, although hard to measure by their nature, may have hit a 40-year low. Since 2007, immigration from Mexico has steadily decreased.

“This more firmly establishes that Mexican immigration has declined and a major reason is that the unauthorized population has fallen,” Randy Capps, Director of US programs at the Migration Policy Institute, said.

“We know border security has been tightened significantly and we also know the draw of the US economy was a lot less –but what’s really interesting is the family ties motivation for returning to Mexico,” Capps said. “That implies that there are a lot of strong social motives for migration. There’s always that draw of the home community.”

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Capps does not expect the net decrease to continue, since in the past year economic conditions in Mexico have deteriorated while the US economy has improved. A drop in oil prices has hurt the Mexican economy.

But even if Mexican immigration rates do increase, both Gonzalez-Barrera and Capps predict that rates would never approach the influx of late last century. Due to a plummeting birth rate, Mexico’s demographics have shifted. “There are fewer young people than there were two decades ago. That’s the reason we’re not expecting the level will go back to what it was,” Gonzalez-Barrera said. Mexicans overall are older, while most people tend to migrate when they’re younger.

As for Donald Trump’s take on all this, his campaign did not return emails and phone calls from VICE News requesting comment.