SCOTT SIMON, HOST:
There's a certain number that's been tossed around a lot this week by Washington, D.C. lawmakers: 11 million. That is the estimated number of undocumented immigrants said to be living in the United States. And it got us thinking. Where does that number come from? And who exactly makes up this 11 million?
NPR's Hansi Lo Wang went in search of the answer.
HANSI LO WANG, BYLINE: If you're looking for numbers on undocumented immigrants in America, there's one guy you have to call.
JEFF PASSEL: My name is Jeff Passel. I'm senior demographer at the Pew Hispanic Center at Washington, D.C.
WANG: And since the late 1970s, Passel has been keeping tabs on a group that actively tries to stay off the radar. But he says, actually, many do participate in the census count and other surveys, so Passel and his demography team crunch data from the Census Bureau, the Department of Homeland Security and other government sources to come up with an estimate. It isn't perfect.
PASSEL: I would say most likely to be too low. The true number might be higher than that.
WANG: The vast majority of that estimated 11 million come from Mexico. Others come from Central America and countries like China, the Philippines and India. Some enter the U.S. illegally and there are many others who come to America legally, says Ruben Rumbaut. He's a sociology professor at the University of California, Irvine, who focuses on immigration.
RUBEN RUMBAUT: Perhaps 40 percent of the 11 million or so are here because they overstay their visas.
WANG: Like Adelaide Tembe, who came to the U.S. as a domestic worker.
ADELAIDE TEMBE: I'm from Mozambique, Africa and I'm a 27-year-old.
WANG: Tembe says her employer abused her, so she left her job five years ago and began living on her own in Maryland, just outside of Washington, D.C.
TEMBE: This is my passport and how I came here to the United States. This is visa they gave to me when I was here.
WANG: And it shows that it expired in 2010.
TEMBE: Yes, expired.
WANG: Tembe says she cleans houses and baby-sits to make money, volunteers at an immigrant advocacy organization, and has adopted a close group of friends as her new family in America. But she misses home.
TEMBE: It's too difficult for me because I cannot see my family, my kids back home, so I hope one day I can go there to see them and come back to America.
JONG-MIN: When I go to sleep I think about it; when I wake up I think about it. I research immigration all day and night.
WANG: Jong-Min is 33 and lives in Brooklyn, New York where he works at his parents' grocery store. He asked us not to use his last name because he's an undocumented immigrant from South Korea. He's also a college graduate. Did you tell your classmates and any friends that you were undocumented?
JONG-MIN: No, no my mom had told me from age 17, don't talk about this ever.
WANG: Jong-Min says he kept his secret until after graduation. He remembers a friend's reaction when he first confessed: I don't have a green card.
JONG-MIN: I couldn't drive, I couldn't vote, I couldn't study abroad. Then he thought, oh, you know what? Your life now makes sense.
WANG: For some parts of the country, the undocumented in America may seem like a distant population, says Ruben Rumbaut.
RUMBAUT: We're a country of over 300 million people and so 11 million might not seem that large a share. But you would be surprised how many people are tied in one way or another to someone who came to the United States in undocumented status.
WANG: And they too have a stake in the future of America's immigration system. Hansi Lo Wang, NPR News.
(SOUNDBITE OF MUSIC)
SIMON: And you're listening to NPR News. Transcript provided by NPR, Copyright NPR.

9(MDAzOTIwODA0MDEyNTA4MTM1OTcyMGJmMA001))