Trump is unveiling his immigration plans at a time when detentions at the nation's southern border are down significantly from levels seen in the late 1990s and early 2000s. The arrest tally last year was the fifth-lowest since 1972. Deportations of people living in the U.S. illegally also increased under President Barack Obama, though Republicans criticized him for setting prosecution guidelines that spared some groups from the threat of deportation, including those brought to the U.S. illegally as children.