U.S. Department of Homeland Security. Office of Immigration Statistics. April 2012.
Naturalization is the process by which U.S. citizenship is conferred upon foreign citizens or nationals after fulfilling the requirements established by Congress in the Immigration and Nationality Act (INA). After naturalization, foreign-born citizens enjoy nearly all the same benefits, rights and responsibilities that the Constitution gives to native-born U.S. citizens, including the right to vote. This Office of Immigration Statistics Annual Flow Report presents information on the number and characteristics of foreign nationals aged 18 years and over who were naturalized during FY 2011.
http://www.dhs.gov/xlibrary/assets/statistics/publications/natz_fr_2011.pdf [PDF Format, 4 pages].