After the passage of the Immigration Reform and Control Act in 1986, many illegal immigrants began to use fake green and Social Security cards. Although the Act did little to curb illegal immigration, it has been a boon for the Social Security System. It is estimated that approximately seven million illegal immigrant workers are now providing the system with $7 billion a year.
See "Illegal Immigrants Are Bolstering Social Security With Billions", Eduardo Porter, The New York Times, April 4, 2005