 According to the Pew Hispanic Center in 2006, an estimated ten percent of all Mexican citizens lived in the United States.The population of Mexican immigrants residing illegally in the United States fell from around seven million in 2007 to about 6.1 million in 2011.This trajectory has been linked to the economic downturn which started in 2008 and which reduced available jobs, and to the introduction of stricter immigration laws in many States.