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An U.S. Customs and Border Protection bike patrol agent assists Mexican's being returned to Mexico after they were apprehended for entering the United States illegally June 2, 2010 in Nogales, Arizona.
Exactly how many unauthorized immigrants are living in the U.S.? It's a number that's difficult to pinpoint, but a new study by the Pew Hispanic Center seeks to give a more complete picture of the immigration flow in recent years.
Jeffrey Passel, lead author of the report, joins the show to explain.