"In 2014, the United States and Mexico experienced a surge in unauthorized migration from Central America, a region that has overtaken Mexico as the primary source for immigrants apprehended at the U.S.-Mexican border. With U.S. support, Mexico has since increased its immigration control efforts. From 2015 to 2017, Mexico apprehended more than 450,000 migrants and asylum seekers from the 'northern triangle' countries. As at the U.S. southwest border, Mexico's apprehensions of migrants from the northern triangle fell in 2017 but increased by 57% in the first half of 2018 as compared to that period last year."
CRS In Focus, IF10215