"This report presents estimates of the legal permanent resident (LPR) population living in the United States on January 1, 2012. The LPR population includes persons granted lawful permanent residence, for example, 'green card' recipients, but not those who had become U.S. citizens. The estimates are shown for the total LPR population and the LPR population eligible to apply to naturalize by country of birth, state of residence, and the year LPR status was obtained. Data for the estimates were obtained primarily from administrative records of U.S. Citizenship and Immigration Services (USCIS) of the Department of Homeland Security (DHS). The methodology used for the 2012 estimates is similar to that used in previous DHS estimates."
U.S. Department of Homeland Security: http://www.dhs.gov/