SYLVIE DOUGLIS, BYLINE: This is PLANET MONEY from NPR.
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DONALD TRUMP: Thank you. Wow. Beautiful...
AMANDA ARONCZYK, HOST:
It is political rally season again.
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TRUMP: It's not too hot out here, right? You know, it's not bad.
ARONCZYK: Former President Donald Trump has been traveling - Michigan, Wisconsin. And recently, he made a stop in Nevada.
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TRUMP: Did you see we put out a notice saying don't come? So only 20,000 people showed up.
ARONCZYK: And like pretty much every Trump rally...
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TRUMP: This open border. So many bad things, but this open border situation where you're allowing millions and millions of people to flood our country.
ARONCZYK: ...Immigration comes up pretty quickly.
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TRUMP: Virtually 100% of the new jobs under Biden have also gone to illegal aliens. Did you know that? A hundred percent.
JEFF GUO, HOST:
To be clear, it is not 100%. But Trump doesn't just claim that immigrants are taking jobs from Americans. He says they're also making wages go down.
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TRUMP: Real wages of African Americans and the workers from all over the world that came here legally, they're down 6% under Crooked Joe. And, you know...
GUO: Immigration is a huge issue for both parties this election year, as the southern border is overwhelmed with people trying to claim asylum. And here at this rally, Trump is pointing to one of the central arguments of his campaign - I'm sure you've heard this one before - that immigrants are hurting the labor market.
ARONCZYK: Actually, he said it again Thursday night in the first presidential debate.
GUO: Right.
ARONCZYK: But politicians aren't the only ones who fight about this. Economists have actually been trying to answer this question for decades. Do immigrants take jobs and lower wages? In fact, it is the subject of one of the most contentious debates in the field of economics. Hello, and welcome to PLANET MONEY. I'm Amanda Aronczyk.
GUO: And I'm Jeff Guo. What happens when hundreds or thousands of new workers enter the workforce? Does it hurt American workers? This question is notoriously difficult to study. Labor markets are these huge, complex systems. And for years, economists had to theorize about immigration's effect, but they struggled to prove anything definitive.
ARONCZYK: Then, almost 45 years ago, something unexpected happened that created a near-perfect experiment to study this very question. A hundred twenty-five thousand Cuban immigrants suddenly showed up on the shores of southern Florida, and they started looking for jobs.
GUO: Today on the show, decades and decades, and many academic papers later, the field is still fighting over how those new arrivals changed the economy - and what it means for our understanding of immigration today.
ARONCZYK: The story of this natural experiment that completely changed our understanding of immigration's effect on the economy - it begins April 1980 in Cuba. Fidel Castro has been dictator for around two decades, and the promise of the revolution is starting to fade. The economy is on the decline. People are being sent to prison for all sorts of small infractions. And if you want to leave Cuba, you need an exit visa, which in 1980 was nearly impossible to get.
GUO: So one way that people were trying to get out of the country was to somehow get inside a foreign embassy and to claim asylum. But the Cuban police would try to stop them. Then, one day, a few guys commandeer a bus and ram past security and through the gates of the Peruvian embassy in Havana.
ARONCZYK: And once the gates had been busted down, thousands of other Cubans joined them.
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UNIDENTIFIED REPORTER #1: In Havana today, the strange story of the Embassy of Peru continued, as many as 10,000 Cubans squatting on the embassy lawn, seeking permission to leave...
ARONCZYK: Now, Castro, he saw these people as disloyal, not committed to his communist revolution. So he's like, fine, you want to go? Go. He announces that anyone can leave Cuba, as long as they can get picked up in a boat at the Port of Mariel.
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DIANA GONZALEZ: Cuba, the Bay of Mariel, 25 miles west of Havana. This morning, nearly 200 Cubans were being loaded onto four boats bound for Florida.
GUO: Over the next few months, hundreds and thousands of Cubans pile into boats to make the journey to Florida, an event that would come to be known as the Mariel boatlift.
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UNIDENTIFIED REPORTER #2: It is an all-too-familiar sight, a motley assortment of boats awaiting a turn at dock space, customs, immigration - 110,000 crammed aboard anything that will float.
ARONCZYK: By the time the governments of both countries agree to stop the flow of migrants, 125,000 Cubans have arrived in Florida, and a lot of them end up in Miami. Most are low-skilled workers with a high school diploma or less. And almost immediately, they're allowed to work.
GUO: Which means that practically overnight, the workforce in Miami grew by about 8%. That's a huge jump, what economists would call an immigration shock.
ARONCZYK: And one economist in particular saw this shock as an opportunity to answer some fundamental questions about immigration.
DAVID CARD: It's big. It's very quick. It's all over in a couple of months. And it was completely unexpected. So that's perfect for, I guess, what you would call a natural experiment.
GUO: This is the Nobel Prize-winning economist David Card. He's an emeritus professor at UC Berkeley, and he is one of the people who pioneered the whole idea of using natural experiments to study the economy.
ARONCZYK: One of the tough things about being an economist is that it's really hard to prove that anything really causes anything else. The economy is so complicated that it's tricky to untangle all the correlations in the data. And the economy is so big that you usually can't run what scientists call a randomized controlled trial.
GUO: But what Card and his colleagues had started to notice back in the day was that if you looked closely at what was happening in the world, there would be these big unexpected events, events that radically shifted the economy in a short period of time, as if some cosmic scientist had set up an experiment just for them to study.
CARD: I started thinking about immigration that way and said, well, maybe the Mariel boatlift would be a way to think about that approach for studying the effect of immigrants.
ARONCZYK: Card realized if he compared Miami to similar cities just before and then after the boatlift, he could maybe answer that central question - how do immigrants impact a labor market? And more specifically, do they make unemployment go up and wages go down?
GUO: Now, the prevailing assumption at the time was that the labor market would follow, you know, the basic rules of supply and demand.
CARD: So if you increase the supply of one group of workers, everybody in that bucket of workers will probably have their wage reduced somewhat in a very, very simple standard-type model.
ARONCZYK: So, for example, let's say, all of a sudden, there are more people in town who want to work in construction. The assumption is that employers will be able to pay less for construction workers. So wages in that industry are going to fall.
GUO: And if you assume that the supply of jobs is fixed, then this model would also predict that an influx of immigrants would make some current workers lose their jobs.
CARD: The most extreme version of it is if there's 100 jobs in the labor market, you bring in 10 immigrants, so 10 natives are going to lose their job. So we call that the skating rink model.
ARONCZYK: The skating rink model, like in ice hockey. David Card is originally from Canada. So am I. We are required to make a reference to hockey. So in hockey, there are six players on the ice. You can swap them out, but you can't have more than six. So the assumption of immigration is that each new immigrant knocks a native off the ice.
GUO: But David Card wasn't convinced that immigration necessarily followed, you know, the basic laws of supply and demand. And the Mariel boatlift seemed like a perfect way to investigate that.
CARD: So I thought it was - in many ways, it was kind of ideal.
ARONCZYK: He pulls six years of data from the census from 1979 to 1985, looks at race, education level, hourly wages, compares Miami to four other cities that did not experience any immigration shocks.
GUO: And what he finds is that the influx of people from the Mariel boatlift has virtually no effect. Wages didn't go down. Unemployment didn't go up.
ARONCZYK: Even when he looked at the group of workers who he thought would be most affected by these new arrivals - workers with high school diplomas or less - he couldn't find an impact on their wages at all.
CARD: So I concluded that it was pretty hard to show that the boatlift had a big negative effect on natives.
ARONCZYK: And so the answer is nothing. There was no impact.
CARD: Well, of course, that's not what you would really say if you were writing a scientific paper. What you would say was there's no detectable effect.
ARONCZYK: OK, which is kind of equal to nothing (laughter).
CARD: Yeah. People like to sort of make it simple, yeah.
ARONCZYK: How would you explain that, that all of these people show up and that there's no detectable effect?
CARD: Well, it seems like what goes on is the labor market has absorptive capacity.
GUO: Absorptive capacity, meaning that within a few years, the Cubans were just kind of absorbed into the labor market, and it's not totally clear why. But one theory is that when they arrived, the Cubans didn't just increase the supply of workers. They were also consumers, right? They increased demand 'cause they needed to buy shoes, get haircuts, rent apartments, and that created more jobs.
ARONCZYK: It's like the hockey team gets bigger. More people can skate at the same time.
GUO: Yeah.
ARONCZYK: So Card finds that the arrival of the Cubans is not depressing wages. They're not stealing jobs. And he sets out to publish his work. He doesn't quite realize how big a deal his findings are.
CARD: So I wrote the paper up as what you could call a case study. And it's a very short paper. It doesn't have hardly any fancy things in it. And I sent it to a very modest journal. It's a specialist labor economics journal. And I knew they might give it a - you know, a shot. So I sent it there, and, of course, the referees hated it (laughter).
ARONCZYK: No kidding.
GUO: Referees are the other economists who read and review papers before they publish.
CARD: I've been called all kinds of things in referee reports, yeah.
ARONCZYK: What did they call you?
CARD: A charlatan, among other things, at times.
ARONCZYK: Spoiler alert - this charlatan went on to win the Nobel Prize in Economics in part because of this very paper. This small case study in a, quote, "very modest journal" has become one of the most cited papers in immigration economics.
Do you remember when you first read David Card's Mariel boatlift paper?
MICHAEL CLEMENS: Wow. That paper is iconic, in that it's referred to in most labor economics textbooks in general. It was one of the cornerstones of a whole movement in research.
GUO: This is Michael Clements. He's a professor of economics at George Mason University. And he knows this story very well.
ARONCZYK: We've spent a lot of time discussing, by the way, like, is this the Lady Gaga of papers? Is it the Taylor Swift of - is it Madonna, more iconic, older? I don't know, do you have a celebrity comparison?
CLEMENS: Oh, my gosh. I think it's Hans Christian Andersen who wrote "The Emperor's New Clothes." I'd compare it to that.
ARONCZYK: Yeah. That is not exactly a celebrity icon. I'm guessing Michael doesn't have a subscription to People Magazine. But he has an interesting point. Before David Card's work, most everyone saw the economy the way they were taught to see it, through the basic laws of supply and demand. And they assumed that applied neatly to immigration. They were told the emperor was wearing beautiful clothing, so they saw beautiful clothing.
CLEMENS: A young child says, wait a minute, the emperor is nude. What Card and his colleagues were doing is something like that.
GUO: And after Card reveals that, no, the emperor is not wearing any clothes, that, no, this basic supply-demand stuff doesn't always apply to immigration, that starts to become a popular view among economists.
ARONCZYK: But the most well known and respected economist looking at immigration at the time disagreed with David Card. His name is George Borjas. Here he is being interviewed on C-SPAN.
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EDWARD ALDEN: Our guest today is one of the country's preeminent economists studying the impact of immigration to the United States. Welcome, Professor Borjas.
GUO: George Borjas is a professor at Harvard. His papers are heavily cited. He wrote the textbook on immigration economics.
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ALDEN: How was it that you came to gravitate to this particular subject?
GEORGE BORJAS: Great question to start with. I was born in Cuba. So am I myself an immigrant.
ARONCZYK: David Card published the Mariel boatlift paper, Borjas had already been studying immigration's effect on the economy for years. And he took issue with the idea that one natural experiment could tell, like, this whole story. Like, what if just looking at Miami was too narrow? What about all the immigrants who left Miami and took jobs elsewhere? And ultimately, who's to say what happened in Miami would happen in other cities?
GUO: Yeah. You see, Borjas preferred to look at the big picture, use big nationwide datasets. And in his work, he had found that the basic laws of supply and demand did apply to immigration, that sometimes immigrants can hurt American workers.
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BORJAS: Look, there are trade-offs. Immigration is not like manna from heaven. There are going to be winners and losers. Some people are going to win. Some people are gonna going to lose.
GUO: By the way, we asked George Borjas for an interview several times, and he declined.
ARONCZYK: Anyways, he and David Card spend years publicly disagreeing with each other about immigration.
GUO: And this simmering tension, it culminates in 2015. That is when Borjas decides to investigate the Mariel boatlift himself, crack open the data and look for his own results.
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BORJAS: So I decided as to actually go back to Mariel. And that's what - actually what I spent all of summer 2015 doing, revisiting the Mariel experiment by looking specifically at high school dropouts.
ARONCZYK: Borjas wanted to do things differently than David Card had. He thought Card had missed something, that he didn't look closely enough at the people who would be most affected by the new arrivals, people who were primarily lower skilled and less educated.
GUO: So while Card had lumped high school graduates and dropouts together in his paper, Borjas wanted to look only at the people who hadn't finished high school.
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BORJAS: In other words, let's focus on what happened to the economic opportunities of high school dropouts. Remarkably enough, David Card did not do that. And remarkably enough, nobody else had done that in the last 25 years.
ARONCZYK: And what he found was different.
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BORJAS: You see a remarkable drop in the wage of high school dropouts in Miami. You find the labor market impact is precisely what you would expect and what common sense tells you. You get a lot more low-skill workers; the low-skill workforce in Miami actually did worse off as a result of that.
ARONCZYK: This is not the big fat nothing that David Card found. Borjas says the wage of high school dropouts in Miami collapsed dramatically by 10- to 30%. There was a huge negative effect.
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ARONCZYK: In Borjas' analysis of the data, immigrants suddenly showing up in a labor market - they do make wages drop for the lowest-skilled workers.
GUO: Overturning David Cards' study - and with it, his pro-immigration findings - was bold and controversial, and not just in the field of economics. In fact, this paper, it started to reverberate in the outside world.
CLEMENS: That's very unusual. Extremely few economics papers get that kind of attention in the public discussion. It was a firestorm.
GUO: That is coming up after the break.
ARONCZYK: After George Borjas publishes his bombshell paper, saying that immigration can make wages drop, it gets picked up by all sorts of media.
CLEMENS: I remember Ann Coulter specifically commenting on this Borjas paper, saying that it, quote, "nuked," unquote, the arguments of the pro-immigration crowd.
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ANN COULTER: I don't care how many economists are going to tell me that somehow they've managed to repeal the laws of supply and demand. You have more of something, the price goes down.
GUO: Michael Clemens and his colleagues watched as Borjas became kind of the go-to economist for the right.
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JEFF SESSIONS: Dr. Borjas at Harvard has written about that. I think he's...
GUO: Borjas was also a favorite of Jeff Sessions, who was a U.S. attorney general under Trump.
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SESSIONS: He's the world's, perhaps, most effective and knowledgeable scholar. And he says that does happen. Wages can be diminished. And one of the...
GUO: Trump was already consulting Borjas about immigration when he ran for office in 2016.
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TRUMP: Decades of record immigration have produced lower wages and higher unemployment for our citizens, especially for African American and Latino workers.
ARONCZYK: Once Trump was in office, when journalists pushed the administration to justify his anti-immigration policies...
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UNIDENTIFIED REPORTER #3: Cite for me, if you could, one or two studies with specific numbers that prove the correlation between those two things 'cause your entire policy is based on that.
ARONCZYK: ...Trump's advisers, like Stephen Miller, would lean on George Borjas' work.
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STEPHEN MILLER: I think the most recent study I would point to is the study from George Borjas that he just did about the Mariel boatlift.
CLEMENS: Stephen Miller cited it by name from the White House podium. That's very unusual for an economics paper. It was a sign of the tremendous influence of Borjas.
GUO: While policymakers and the media were busy talking about Borjas' explosive findings, some economists were skeptical of what Borjas found.
JENNIFER HUNT: I did read the entire paper, and I had concerns about the claims of overturning the original results.
ARONCZYK: Jennifer Hunt is a professor of economics at Rutgers University. She's one of the leading economists studying immigration. And she's primarily an academic, but she also spent two years working for the Obama administration.
GUO: Around 2016, Jennifer Hunt and Michael Clemens are talking with each other when they realize that they have similar thoughts about Borjas' work on the Mariel boatlift.
HUNT: Michael Clemens contacted me to ask what I had thought of this paper, and I said that I had concerns. And he convinced me that we should write a paper about our concerns.
ARONCZYK: It was the war of the papers. So they team up together to look very closely at what Borjas did - how he interpreted the Mariel data.
GUO: And their main critique had to do with Borjas' decision to focus on a very narrow subset of people, 'cause if you look closely at Borjas' paper, it's clear that choosing to look at workers without a high school degree wasn't the only choice that Borjas made. He also narrowed his sample down to some very specific demographic categories.
CLEMENS: Men who are prime-age workers - basically 20s to 50s and not teenagers, not older workers - who are not just low-skill - that is, they don't have college degrees, but they don't even have high school degrees - and they're not Hispanic - this is the very, very, very small slice of the labor market in Miami that Borjas was looking at.
ARONCZYK: And why carve off people who are Hispanic?
CLEMENS: That's a great question.
ARONCZYK: This is the most controversial choice that Borjas made - to take out all Hispanic people from the data set. And the result of all this slicing and dicing of the data was an average sample size of 17 workers per year.
GUO: Now, there are a few ways to understand this 'cause economists are always making these kinds of choices. When they want to make comparisons, they might slice up the data to make things more, you know, apples to apples. Borjas argued that he took out Hispanic people to make the cities in his study more comparable. That was a choice. But Clemens argues that it was not a good choice.
CLEMENS: If you are analyzing the effects of Hispanic workers flooding into Miami, the very first place you would look would be for effects on other Hispanic workers. That's a universal finding of immigration economics. If there's going to be competition between new immigrants and other workers in any labor market, the very first place you would look at is other immigrants.
ARONCZYK: So they would be the people - so I get it; they would be the people most impacted, is other Hispanic workers who are already there?
CLEMENS: Definitely. So at the very least, if you wanted to write a rigorous and transparent study, you would start by looking at the effects on Hispanic workers.
ARONCZYK: Clemens and Jennifer Hunt publish, put their stake in the ground. And while there are apparently no chairs flying at conferences or actual fist fights, there are some bad feelings and maybe some reputational harm, which is pretty dramatic for economics.
GUO: In fact, around this time, a movement was already underway to resolve these disputes within immigration economics. The National Academy of Sciences had decided to bring together the leading experts to try to come to a consensus.
ARONCZYK: George Borjas was invited, as was Jennifer Hunt.
HUNT: It's exciting because it's a great thing to try to come to consensus.
ARONCZYK: But how does one get to consensus? Like, do you vote? Do you just kind of, like, debate?
HUNT: Well, you can't - consensus means not voting because it means everyone needs to agree.
ARONCZYK: Right.
HUNT: So...
ARONCZYK: Right. Good point. Right (laughter).
GUO: This group of experts worked together for more than 2 1/2 years. They read all the most important papers. They debated, they argued. And some of the most contentious stuff, as you might have guessed, was about the impact of immigrants on wages.
HUNT: That was where we had, yeah, some discussions, shall we say, that were animated, I'll call them.
ARONCZYK: But in the end, the experts, including Borjas, they did actually come to an agreement.
HUNT: The breakthrough in this issue was we came to a consensus that there's little or no impact of immigration to the U.S. on average wages.
ARONCZYK: OK.
HUNT: So I think that was the big breakthrough.
GUO: The consensus that they finally arrived at was, quote, "the long-term impact of immigration on the wages and employment of native-born workers overall is very small" - basically, a version of what David Card had originally found - that big, fat nothing.
ARONCZYK: So you guy you guys did it. You resolved the dispute.
HUNT: We did. So I'm proud of our work, and I'm, you know, both honored and happy to have been associated with it. And then the next thing that happened was that Borjas put commentary on his own website.
ARONCZYK: Oh.
GUO: Yeah. So the day after the report is published, Borjas takes to the internet to give his own take. He says that the consensus report is flawed and takes issue with that core finding.
HUNT: He said that he didn't agree with things that were written in the consensus report.
ARONCZYK: So after all of that, Borjas undermined the consensus.
HUNT: Yes.
ARONCZYK: How did that make you feel?
HUNT: Well, I was very unhappy because I just told you how happy I was that we had come to a...
ARONCZYK: Right.
HUNT: ...Consensus.
ARONCZYK: Right.
HUNT: So I was very unhappy about that.
ARONCZYK: That was eight years ago. Since then, economists have continued to poke at these core questions, and they've even continued to weigh in on the Mariel boatlift. In fact, just earlier this year, another big-time economist used some fancy new methodology and new data to find once again that the arrival of immigrants didn't hurt wages.
GUO: And more broadly, over the past few decades, the field of economics has kind of coalesced around this one central idea, which is that whether you're talking about jobs or wages or growth or productivity, that immigrants are generally good for the economy.
ARONCZYK: In some ways, though, it doesn't quite matter what all of these papers say in the political fight over immigration.
HUNT: When I worked in the Obama administration, I noticed that academic work does have an effect, which was heartening. But what was less heartening was that I realized it doesn't actually change anyone's minds. It's just that it serves as support for people whose minds are already made up.
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HUNT: They're always citing papers that support what they thought before.
ARONCZYK: Right now, politicians across the country are running on anti-immigration platforms, promising to shut down the border, to limit immigration, to protect your job, protect your wages. And when they're pushed to justify it, they still have a paper frozen in time that they can point to.
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GUO: Today's episode was produced by Willa Rubin and edited by Annie Brown. It was engineered by Valentina Rodríguez Sánchez and fact-checked by Sierra Juarez. Alex Goldmark is our executive producer.
ARONCZYK: Special thanks this week to Professor Francine Blau, to Professor Joan Monras, to the Wolfson Archives and to Connor O'Neill from NPR's White Lies podcast team. White Lies produced a series about the Mariel boatlift. It is a great listen. You should go subscribe.
GUO: It's amazing.
ARONCZYK: I'm Amanda Aronczyk.
GUO: I'm Jeff Guo. This is NPR. Thanks for listening.
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