U.S. immigration law is a complex amalgamation of statutes, regulations and case law that is in a constant state of flux. These laws are established by the federal government and dictate who may enter the United States and how long they may stay. They also govern the process by which individuals can become naturalized citizens and what happens when foreign nationals enter the country without permission or overstay their permitted visas.
Department of Homeland Security (2016). Persons Obtaining Legal Permanent Resident Status By Class Of Admission: 2000 To 2013 [Selected Fiscal Years Ending September 30] ProQuest Statistical Abstract of the U.S. 2016 Online Edition. Retrieved from
http://statabs.proquest.com/sa/docview.html?table-no=48&acc-no=C7095-1.1&year=2016&z=3669A6E9C3EDC606AAD06E48361F6FA7FEA822EB