GWEN IFILL: The immigration debate cuts both ways. As Tom mentioned in his story, illegal border crossings are actually down. That's one fact documented in a new study.
Margaret Warner has more.
MARGARET WARNER: That new study is from the Pew Hispanic Center, and its findings are surprising.
Between 2005 and 2010, the wave of Mexican immigrants, legal and illegal, into the U.S. was offset by an equal number of Mexican migrants returning home. This new equilibrium partly reflects lower Mexican immigration into the U.S., from 770,000 at its peak in 2000 to just 140,000 in 2010.
But it also reflects an increase in the number of returnees to Mexico, some 1.4 million between 2005 and 2010.
And for more on the numbers and what's behind them, we go to Jeffrey Passel, a senior demographer at the Pew Hispanic Center and a co-author of the report.
And welcome. This is a fascinating report.
JEFFREY PASSEL, Pew Hispanic Center: Thank you very much.
MARGARET WARNER: Now, you've been studying immigration in the United States for decades. Headline on this, "Net migration from Mexico falls to zero, perhaps less."
Did you ever think you would live to see this?
JEFFREY PASSEL: It's a real surprise.
The numbers have been just steadily going up for 40 years year after year. And it was a question of how much. We got to over 12 million Mexicans living in the United States in 2007. That's the largest wave in history, really, more than we have had for many other countries and more than any other country has immigrants at all.
So it. . .
MARGARET WARNER: Throughout the centuries.
JEFFREY PASSEL: Yes.
MARGARET WARNER: Well, let's look at the trends separately. First, the dramatic drop in the inflow, now, what's behind that?
JEFFREY PASSEL: Well, we've seen -- when we have looked at the numbers year by year, we see a lot of relationship between the state of the U.S. economy and the inflow from Mexico.
So the peak in 2000 was at very low unemployment, very large job creation, and lots of Mexicans were coming into the country. And as the economy got better, the numbers went up. We hit a recession, the numbers went down some. In 2007, they started dropping off the table.
MARGARET WARNER: But is the economy better in Mexico?
JEFFREY PASSEL: In general, it hasn't been. They, too, suffered from the recession.
But in the last couple of years, it has gotten better. There are a lot of factors that work here. The economics are a big one. Enforcement makes a difference as well. We have seen the numbers increase over some periods where enforcement went up. But enforcement has really hit very high levels in the last couple of years.
And when you put the two factors together, if it's more expensive, it's more dangerous, it's more difficult to get in and if you can't get a job in the U.S., then you may just not try. And that seems to be behind these numbers.
MARGARET WARNER: Given the hardship.
And you also pointed out because of the declining birthrate in Mexico, you also over time are getting a smaller pool of young men.
JEFFREY PASSEL: We're at the very beginning of that.
MARGARET WARNER: Oh. So that hasn't affected it yet?
JEFFREY PASSEL: It's started a little bit. Mexican fertility was seven children per woman in 1970. It's now down to 2.4 children per woman.
MARGARET WARNER: Why?
JEFFREY PASSEL: And as a result, beginning in the mid-'90s, the number of births each year got a little smaller. Those are now the people starting to enter the labor force. So there's not as many next year as there were this year, and so on. And that's going to play out in the future. But we're right at the beginning of that.
MARGARET WARNER: So let's talk now about the other finding, which is the greater number of returnees back to Mexico.
Now, who are they? Something like 1.4 million, as I think I said in the intro, in the last five years.
JEFFREY PASSEL: That's right.
MARGARET WARNER: Who are they and why are they going back?
JEFFREY PASSEL: Well, this was a big surprise to us. It's a result that showed up first in the Mexican census.
About half of these are entire families moving back. They're not moving back in with relatives. They're not going back into existing households. They're setting up their own households. So they're families with children. About 300,000 of them are actually children who were born in the United States to Mexican immigrants. So those people are citizens of both countries.
MARGARET WARNER: So they have every right to stay here, yet they're going back.
JEFFREY PASSEL: Well, they're children. They're children. And. . .
MARGARET WARNER: Oh, I see. They're not grown children?
JEFFREY PASSEL: No, no. There are -- a couple hundred thousand are under 5. So it's families that are going back now.
MARGARET WARNER: How much of the return is driven also by deportation, involuntary return?
JEFFREY PASSEL: Well, some. It's a number that's very hard to tease out of the available data.
We put a rather wide range on it. Maybe as little as 5 percent, but as much as a third of the migration back might be involuntary. The enforcement from the federal government has increased over the last five or six years, and larger numbers of people are being deported back formally to Mexico.
MARGARET WARNER: Before we go -- and I know you're not in the prediction business, but we saw great waves of German and Irish immigration over a century ago tail off. Do you think this is a long-lasting enough trend that it really represents the tailing off of the great wave of Mexican immigration?
JEFFREY PASSEL: Well, the demographic factors we talked about are such that, as we go into the future, there won't be as many potential migrants to come into the United States.
I don't think we will ever get back to the levels we saw in 2000. I doubt that we'll get no immigrants, but I would be very surprised if it ramped up a lot in the future.
MARGARET WARNER: Even if the economy picked up.
Well, Jeffrey Passel of the Pew Hispanic Center, thank you.
JEFFREY PASSEL: Thank you very much.