As calls to eliminate birthright citizenship grow louder, a new report from the Pew Hispanic Center crunches the numbers on just how many illegal immigrants give birth in the U.S. The Center's findings:

An estimated 340,000 of the 4.3 million babies born in the United States in 2008 were the offspring of unauthorized immigrants ...

Unauthorized immigrants comprise slightly more than 4% of the adult population of the U.S., but because they are relatively young and have high birthrates, their children make up a much larger share of both the newborn population (8%) and the child population (7% of those younger than age 18) in this country. ...

The new Pew Hispanic analysis finds that nearly four-in-five (79%) of the 5.1 million children (younger than age 18) of unauthorized immigrants were born in this country and therefore are U.S. citizens. In total, 4 million U.S.-born children of unauthorized immigrant parents resided in this country in 2009, alongside 1.1 million foreign-born children of unauthorized immigrant parents.

Read the summary at the Pew Hispanic Center and the full report here.