Human beings leave their homelands for many reasons and they are called by many names: illegal aliens, strangers, asylum-seekers, displaced persons, economic migrants, lawful permanent residents, refugees, temporary workers, and victims of trafficking. Some are forced to flee because of violence, persecution, natural disaster, or intense economic privation. Most migrate in search of a better life, many as part of a family survival strategy. The movement of people from one place to another has remained a constant feature of human history. In an era characterized by the fast and cheaper...