WASHINGTON (CBSDC) —  The number of people from Mexico attempting to cross the border illegally has declined nationwide, according to a new study from Pew Research Center.

As immigration remains a highly debated issue among presidential candidates, the study takes a look at unauthorized immigrants entering the U.S., their participation in the labor force, and where in the U.S. they are settling.

The study found that 5.9 million illegal immigrants from Mexico lived in the U.S. in 2012, about 1 million fewer than 2007. Though Mexicans still made up 52 percent of unauthorized immigrants in 2012, illegal immigration has overall leveled off over the years, with more Mexicans leaving the U.S. than arriving.

For the first time on record, Pew found that more non-Mexicans than Mexicans were apprehended at the border during 2014. In 2014, 229,178 Mexicans were apprehended, a stark contrast from the 1.6 million apprehended in 2000. The study suggests that the decline in apprehensions indicates a decrease in the number of unauthorized Mexican immigrants attempting to cross the border.

Despite illegal immigration from Mexico being down nationwide, deportations of Mexican immigrants reached a record high in 2013 of 314,904, up from 169,031 in 2005, according to the study.

Although unauthorized immigrants from Mexico make up a slight majority nationwide, they account for 75 percent of the total unauthorized immigrant population in 10 states: New Mexico, Arizona, Idaho, Wyoming, Colorado, Oklahoma, Wisconsin, Kansas, Oregon and Texas. The study notes that half of these states saw a decline in illegal immigrant population from 2009 to 2012.

The new data comes as many Democrats are fighting to support a pathway to citizenship backed by President Barack Obama, while Republicans largely oppose these policies.

Republican presidential candidate Donald Trump sparked a media frenzy and scrutiny from fellow politicians after making controversial comments about Mexican immigrants in his campaign announcement speech. Trump will be visiting the Mexican border on Thursday.