More Mexicans are now leaving the U.S. than are coming into the country.

While tougher enforcement of immigration laws has been a significant factor in the reversal, most of the departing Mexicans are leaving on their own, a Pew Research Center report said Thursday.

Citing Mexican census figures, the report found that 1 million Mexicans and their families (including U.S.-born children) left the U.S. for Mexico from 2009 to 2014. It said that U.S. census data for the same period shows an estimated 870,000 Mexicans entered the U.S.

Pew's findings accounted for both documented and undocumented immigrants.

Among the most common reasons Mexicans are saying adiós to the USA are a slow economic recovery here and the fact that they miss their families back home, the study found.

In the past it was easier for immigrants to visit their families and return to the U.S. But with increased border enforcement, they remain in the U.S. until family ties pull them back home, said Ana Gonzalez the author of the report.

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Another factor that may be discouraging northern migration is tougher enforcement of immigration laws at the border and inside the U.S.

"U.S. border apprehensions of Mexicans have fallen sharply, to just 230,000 in fiscal year 2014 -- a level not seen since 1971," the report said.

The number of Mexicans deported through heightened ICE enforcement has spiked. The Obama administration has deported more Mexicans than any other president.

Despite the deportations, the majority of Mexicans who returned to Mexico between 2009 and 2014 have done it of their own volition. The Pew study found that only 14% of those who returned to Mexico in that time period did so because they'd been deported.

While a majority of Mexicans living in Mexico still believe that life is better north of the border, a growing proportion is less impressed with the American Dream.

"Today, a third (33%) of adults in Mexico say those who move to the U.S. lead a life that is equivalent to that in Mexico," the report said.

Mexicans have long represented the largest proportion of immigrants in the United States, but migrants from Asia are now neck and neck with them, according to the study.

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The report also found that some of the characteristics of Mexican immigrants currently living in the United States have changed. It found that they are more settled, older and better educated than they were 10 years ago.