On Tuesday, the Pew Research Center reported that the number of immigrants staying in the United States without permission fell to a ten-year low in 2016. Researchers used government data to show that from 2007 to 2016, the number of undocumented immigrants dropped from 12.2 million to 10.7 million. Pew linked the decrease to a large reduction in the number of Mexicans crossing the U.S. border illegally. However, the number of immigrants from El Salvador, Guatemala and Honduras trying to cross over from Mexico illegally was up. Central America is the only region for which there was an increase in undocumented immigrants during the period of the study. Arrests of Central Americans at the U.S.-Mexico border have also risen. But Pew researchers said arrests remained well below their highest number in 2014.