The rate of undocumented immigrant Mexicans entering the U.S. has been decline for the last eight years.

Based on preliminary estimates from the Pew Research Center, nearly 5.6 million Mexican immigrants lived in the U.S. without legal authorization from the U.S. government. The Mexican undocumented immigrant population peaked in 2007, when 6.9 million were living in the U.S. Therefore, since 2007, more than one million Mexicans are no longer living in the U.S.

According to the Pew Research Center, the undocumented Mexican immigrant population in the U.S. dropped due to a various factors. Border enforcement during 2013 was at an all-time high with approximately 315,000 deportations, which accounted for an 86 percent increase since 2005 data.

The decline could also be subject to Mexicans preferring to enter the U.S. through the legal process. During the 2014 fiscal year, the rate of apprehended Mexican immigrants at the southwest U.S. border fell by nearly 227,000 -- a rate not seen since the early 1970s. Although the rate of Mexican apprehensions dropped, apprehensions of Central American migrants peaked at almost 253,000.

"Although the number of unauthorized immigrants from Mexico has been declining, they still amount to about half of the total U.S. unauthorized immigrant population. Today, unauthorized Mexican immigrants make up a lower share (48 percent) of the Mexican-born population living in the U.S. compared with their peak in 2007 (54 percent)," wrote Pew Research Center's Ana Gonzalez-Barrera.

Data from the 2014 Mexican National Survey of Demographic Dynamics (ENADID) showed one million Mexicans, including families and their U.S.-born children, moved from the U.S. to Mexico. The ENADID survey identified that the importance of family is the primary reason for migrating back to Mexico. Sixty-one percent of respondents who had lived in the U.S. in 2009 said they moved back to Mexico by 2014 to reunite or start a family.

Six percent of ENADID's survey respondents said they returned to Mexico due to employment circumstances, while 14 percent admitted they were deported from the U.S.

"Lack of work in the U.S. was a more important reason for the 180,000 return migrants who lived in Mexico in 2009, left for the U.S. after that, and came back to Mexico between 2009 and 2014," added Gonzalez-Barrera, noting 25 percent of more recent returnees said the main reason they came back was they had not been able to find a job.

Must Read: Mexico Deportation Rate Outpaces US, Most Deportees Are Not Criminals

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