Illegal immigration to the United States
Illegal immigration to the United States is the act by foreign nationals violating United States immigration laws by either entering the country without government permission (i.e., a visa) or once lawfully entering, remaining within the country beyond the termination date of a temporary visa.
The United States Department of Homeland Security (DHS) has estimated that 11.4 million unauthorized immigrants lived in the United States in January 2012. According to DHS estimates, "the number of illegal immigrants peaked around 12 million in 2007 and has gradually declined to closer to 11 million." The DHS estimate "is in the same ballpark as several independent organizations that study illegal immigration, including Pew Research Center (11.3 million); the Center for Migration Studies (11 million), which studies migration and promotes policies that safeguard the rights of migrants, and the Center for Immigration Studies, which advocates for low levels of legal immigration (11-12 million)."