BROOKE GLADSTONE: Back on these shores, the view towards immigrants varied wildly in emphasis and tone. This week in Philadelphia, people with accents were seen and heard in a blaze of welcome empathy.

 [CLIPS]:

KHIZR KHAN:  Donald Trump, have you even read the United States Constitution?

 [AUDIENCE LAUGHTER/CHEERS]

I will gladly lend you my copy.

BROOKE GLADSTONE:  The week before in Cleveland, not so much. DONALD TRUMP:  Nearly 180,000 illegal immigrants with criminal records, ordered deported from our country, are tonight roaming free to threaten peaceful citizens.

BROOKE GLADSTONE:  Myth and reality matter when they create policy, so we turn now to the great and enduring American myths about illegal immigration. Doug Massey is a professor of sociology at Princeton, specializing in immigration. What’s the biggest myth?

PROF. DOUG MASSEY:  The biggest myth today is that it’s still continuing.

 [BROOKE LAUGHS]

In fact, illegal migration ended eight years ago and has been zero or negative since 2008, because migration is a young person's game. If you don't migrate between the ages of 15 and 30, you don't migrate at all, and the average age in Mexico is now 28 years old.

BROOKE GLADSTONE:  Another popular myth is that undocumented immigrants commit a lot of crimes. Do they?

PROF. DOUG MASSEY:  Immigrants, in general, and immigrant neighborhoods, in particular, have very low rates of crime, much lower than native-born people. The US counties along the Mexico-US border are among the safest and most crime-free counties in the United States. And as far as terrorist threat goes, there is no evidence that there’s ever been a terrorist cell or any terrorist that’s ever tried to cross into the United States from Mexico.

BROOKE GLADSTONE:  What about the fact that immigrants steal our jobs? Is that a fact?

PROF. DOUG MASSEY:  Not really. The one group that they compete with in the labor force are low-skilled, high-school-or-less- educated workers. And even in that group the effects are actually quite small. Immigrants actually maintain jobs in the United States that would have gone overseas a long time ago. You’re just not going to get native American workers to go out into the Coachella Valley in 120-degree heat to harvest watermelons. Mexicans and Latinos, more broadly, are the backbone of our agricultural workforce and also the food processing workforce. All the studies show that, on balance, they’re quite a benefit to the United States. They pay taxes. They’re also consumers and create demand, and they provide a variety of services to make Americans more productive, particularly in the fields of childcare, yardwork, healthcare.

I think if people really thought about what it, what they would want to do would be to legalize the 11 million people so their wage rates would rise and they wouldn’t compete unfairly with American workers. At this point, these people have been here on an average of 10 to 20 years, because there hasn't been any new migration for the last eight years. And the majority of these people now have US-born American citizen kids. So by punishing the parents, you're also punishing the kids.

BROOKE GLADSTONE:  People will say, well, the undocumented immigrant population is a big drain on health and social services, school resources, the welfare system. This is something that we heard quite a lot at the Republican National Convention.

PROF. DOUG MASSEY:  It’s not a big drain. Immigrants, in general, are very uninvolved in the welfare system. In fact, legal immigrants are banned for five years from receiving these federally-subsidized services. Undocumented migrants are banned from Obamacare, of course, the Affordable Care Act. The only real expense is emergency medical care.

Schools and healthcare are the two places where they do have an effect because they're young and they have kids. Kids that are born here are American citizen kids. It does create a burden for localities that have large immigrant populations. That could be solved with a revenue-sharing formula that took into account the number of foreign-born in different states and localities. But it’s much easier for politicians to whine about the burdens, rather than actually take care of the burdens using federal revenues. So medical care and schools are the two biggest.

BROOKE GLADSTONE:  Actually, there's a bigger one, that you’ve talked about quite a lot, the cost associated with illegal immigration.

PROF. DOUG MASSEY:  Well, the immigration detention system is now the fastest-growing portion of the American criminal justice complex. For decades, people would come, they’d work for a period and go back. What we did, starting in the mid-1980s was to ramp up border enforcement and really militarize the border between Mexico and the United States. And this drove up the costs and the risks of border crossing to a point where people decided they weren’t going to cross the border anymore, and they did this by staying put in the United States, once they’d made it in, rather than circulating back and forth as they had been.

BROOKE GLADSTONE:  Mm-hmm.

PROF. DOUG MASSEY:  So essentially, in the 1990s, we were spending 3 to 4 billion dollars a year and we doubled the net rate of undocumented population growth.

BROOKE GLADSTONE:  So let us go back even further, to the 1965 US Immigration Act that unintentionally created this flood of undocumented immigration, in the first place, because, as you've written, prior to the mid-60s illegal immigration from Mexico really didn't happen because the US was legally admitting about 50,000 Mexicans a year. So what happened in 1965?

PROF. DOUG MASSEY:  Two things happened in 1965. First, Congress amended the Immigration and Nationality Act, and they did it for good reason. They wanted to get rid of the racist provisions that been put in place in the 19th century and the early 20th century, policies that discriminated against Asians and Africans and Southern and Eastern Europeans. They scrapped the old system and tried to replace it with a, a neutral system that didn't favor any particular country. And they did this by creating a new system where every country got 20,000 visas per year. The quota for legal immigration from Mexico is the same as the quota for Botswana or Nepal. And, of course, Mexico is 130 million people. It’s our second largest trading partner. We share a 2,000-mile border. And it's treated like some of the most distant nations in the world.

BROOKE GLADSTONE:  You say this led, essentially, to the creation of illegal immigration as a thing.

PROF. DOUG MASSEY:  Yeah, in the late 1950s there was no illegal migration from Mexico. The other component of what was going on was a large guest worker program called the Bracero Program.

BROOKE GLADSTONE:  Pretty bad rep, the Bracero Program had. A lot of those immigrants who came into this country to work in agriculture were horribly mistreated and exploited.

PROF. DOUG MASSEY:  Yes, and that's why Congress was acting. Both the repeal of the Bracero legislation and their amendment to the Immigration and Nationality Act were not considered to be immigration law at the time. They were considered to be civil rights policies. They were righting old wrongs. And the Bracero Program came to be seen as an exploitative labor program on a par with southern sharecropping. But what followed was four decades of illegal migration and increasing growing exploitation, far worse than what Bracero migrants experienced back in the 1950s and early ‘60s.

BROOKE GLADSTONE:  So why is immigration such a political flashpoint, if it's not actually a problem?

PROF. DOUG MASSEY:  Well, I think that the United States is in the midst of a very strong and profound demographic transition that has unnerved a lot of older white Americans. You have to remember that the baby boom grew up in the whitest, most native America that’s ever existed. In 1970, the foreign-born percentage of the United States, for the first and only time in American history, fell below 5 percent. And African-Americans were segregated and out of sight. That's the America that people look back and think that that's normal. And that's all changed.

There are two things that happened to create kind of a perfect storm for an anti-immigrant, nativist, xenophobic reaction. One is a rapidly changing demography, which upsets people, especially older people. And the second thing was a massive increase in income inequality. Immigrants are to blame for that. That’s just part of the broader set of changes that have come with a global economy. And the Mexico border has become an all-purpose symbol of a line drawn in the sand by politicians to show their concern about America and its security to voters. But it’s all basically theater.

BROOKE GLADSTONE:  This illegal invasion idea is tied to whatever the perceived security threat of the day happens to be.

PROF. DOUG MASSEY:  Well, immigration has always been used as a ploy in American domestic politics. And when illegal migration rose after 1965, it fit into the discourse perfectly because if migrants are illegal, by definition they’re lawbreakers and criminals. So you find even liberal politicians to call for more border enforcement against whatever the perceived enemy of the day is. During the 1980s, during the Reagan administration, it was Communists and Sandinistas from Central America. Then in the ‘90s and 2000s, it became Al Qaeda, and now it’s ISIS. And most recently, it was Ebola.

BROOKE GLADSTONE:  Let me ask you about the coverage of immigration issues. If you were advising news consumers on red flags in coverage that people should be very wary of?

PROF. DOUG MASSEY:  The first thing to look for is somebody trying to scare you. The second is who are they citing, where are they getting their information, if at all? Media coverage tends to present this side and that side, and they present them as equivalent. Look at the organizations that are producing the information. Organizations that have a self-interested stake in portraying immigration as bad, I don't think can be trusted.

The Center for Immigration Studies, Numbers America (NumbersUSA), they’re validly anti-immigrant. They take census data but then they twist it in ways that are really misleading.

BROOKE GLADSTONE:  Mm-hmm. And what’s an organization that does good work?

PROF. DOUG MASSEY:  The Pew Research Center in Washington, DC. Pew Research Center is nonpartisan. It employs highly-qualified demographers and social scientists to analyze the data, to provide a factual basis for understanding important public policy issues. And another obvious source is the US National Academy of Sciences.

BROOKE GLADSTONE:  What about people who want their nation back, can they get it back with a wall or through deportations?

PROF. DOUG MASSEY:  That cow’s out of the barn. Even if we cut off the immigrants completely today, we would still undergo a gradual process by which the United States would become a majority minority society where whites are no longer a majority.

BROOKE GLADSTONE:  So the people who want their country back, they can’t have it.

PROF. DOUG MASSEY:  No, but if you listen to the rhetoric in the 1920s, old-line WASP leaders said, if we don't stop this immigration now we’re going to become an Italian and Polish nation. And okay, there's lots of Italians and Polish-Americans today, but nobody sees them as different, as un-American. And the same thing will happen with Latinos and Asians. It will probably be a very different America, with very different words to describe who we are as a people and what kind of social categories exist within it, but it’s not going to go back to the 1970 period, where it was only 4.7 percent immigrants and Blacks were segregated, Asians were out of sight and Latinos were a small percentage of the population. That world is gone for good, and there's nothing you can do about it, except adapt and make it work for you.

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BROOKE GLADSTONE:  Doug, thank you very much.

PROF. DOUG MASSEY:  Thanks. Good luck with the report.

BROOKE GLADSTONE:  Doug Massey is a professor of sociology at Princeton, specializing in immigration.

Coming up, a peculiar media rule meant to protect minorities and immigrants in Germany may actually be making things worse. This is On the Media.