2019.07.17 将修复美国梦的经济学家

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THE ECONOMIST WHO WOULD FIX THE AMERICAN DREAM
No one has done more to dispel the myth of social mobility than Raj Chetty. But he has a plan to make equality of opportunity a reality.

By Gareth Cook
AUGUST 2019 ISSUE
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Updated at 3:47 p.m. ET on July 17, 2019.

Raj chetty got his biggest break before his life began. His mother, Anbu, grew up in Tamil Nadu, a tropical state at the southern tip of the Indian subcontinent. Anbu showed the greatest academic potential of her five siblings, but her future was constrained by custom. Although Anbu’s father encouraged her scholarly inclinations, there were no colleges in the area, and sending his daughter away for an education would have been unseemly.

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But as Anbu approached the end of high school, a minor miracle redirected her life. A local tycoon, himself the father of a bright daughter, decided to open a women’s college, housed in his elegant residence. Anbu was admitted to the inaugural class of 30 young women, learning English in the spacious courtyard under a thatched roof and traveling in the early mornings by bus to a nearby college to run chemistry experiments or dissect frogs’ hearts before the men arrived. Anbu excelled, and so began a rapid upward trajectory. She enrolled in medical school. “Why,” her father was asked, “do you send her there?” Among their Chettiar caste, husbands commonly worked abroad for years at a time, sending back money, while wives were left to raise the children. What use would a medical degree be to a stay-at-home mother?

In 1962, Anbu married Veerappa Chetty, a brilliant man from Tamil Nadu whose mother and grandmother had sometimes eaten less food so there would be more for him. Anbu became a doctor and supported her husband while he earned a doctorate in economics. By 1979, when Raj was born in New Delhi, his mother was a pediatrics professor and his father was an economics professor who had served as an adviser to Prime Minister Indira Gandhi.

When Chetty was 9, his family moved to the United States, and he began a climb nearly as dramatic as that of his parents. He was the valedictorian of his high-school class, then graduated in just three years from Harvard University, where he went on to earn a doctorate in economics and, at age 28, was among the youngest faculty members in the university’s history to be offered tenure. In 2012, he was awarded the MacArthur genius grant. The following year, he was given the John Bates Clark Medal, awarded to the most promising economist under 40. (He was 33 at the time.) In 2015, Stanford University hired him away. Last summer, Harvard lured him back to launch his own research and policy institute, with funding from the Bill & Melinda Gates Foundation and the Chan Zuckerberg Initiative.

Chetty turns 40 this month, and is widely considered to be one of the most influential social scientists of his generation. “The question with Raj,” says Harvard’s Edward Glaeser, one of the country’s leading urban economists, “is not if he will win a Nobel Prize, but when.”

The work that has brought Chetty such fame is an echo of his family’s history. He has pioneered an approach that uses newly available sources of government data to show how American families fare across generations, revealing striking patterns of upward mobility and stagnation. In one early study, he showed that children born in 1940 had a 90 percent chance of earning more than their parents, but for children born four decades later, that chance had fallen to 50 percent, a toss of a coin.

In 2013, Chetty released a colorful map of the United States, showing the surprising degree to which people’s financial prospects depend on where they happen to grow up. In Salt Lake City, a person born to a family in the bottom fifth of household income had a 10.8 percent chance of reaching the top fifth. In Milwaukee, the odds were less than half that.


Chetty at age 9. He was later valedictorian of his high school, and he went on to earn an undergraduate degree and a doctorate in economics from Harvard University. At age 28, he was among the youngest faculty members in the university’s history to be offered tenure. (Courtesy of Raj Chetty)
Since then, each of his studies has become a front-page media event (“Chetty bombs,” one collaborator calls them) that combines awe—millions of data points, vivid infographics, a countrywide lens—with shock. This may not be the America you’d like to imagine, the statistics testify, but it’s what we’ve allowed America to become. Dozens of the nation’s elite colleges have more children of the 1 percent than from families in the bottom 60 percent of family income. A black boy born to a wealthy family is more than twice as likely to end up poor as a white boy from a wealthy family. Chetty has established Big Data as a moral force in the American debate.

Now he wants to do more than change our understanding of America—he wants to change America itself. His new Harvard-based institute, called Opportunity Insights, is explicitly aimed at applying his findings in cities around the country and demonstrating that social scientists, despite a discouraging track record, are able to fix the problems they articulate in journals. His staff includes an eight-person policy team, which is building partnerships with Charlotte, Seattle, Detroit, Minneapolis, and other cities.

For a man who has done so much to document the country’s failings, Chetty is curiously optimistic. He has the confidence of a scientist: If a phenomenon like upward mobility can be measured with enough precision, then it can be understood; if it can be understood, then it can be manipulated. “The big-picture goal,” Chetty told me, “is to revive the American dream.”

Last summer, I visited Opportunity Insights on its opening day. The offices are housed on the second floor of a brick building, above a café and across Massachusetts Avenue from Harvard’s columned Widener Library. Chetty arrived in econ-casual: a lilac dress shirt, no jacket, black slacks. He is tall and trim, with an untroubled air; he smiled as he greeted two of his longtime collaborators—the Brown University economist John Friedman and Harvard’s Nathaniel Hendren. They walked him around, showing off the finished space, done in a modern palette of white, wood, and aluminum with accent walls of yellow and sage.

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Later, after Chetty and his colleagues had finished giving a day of seminars to their new staff, I caught up with him in his office, which was outfitted with a pristine whiteboard, an adjustable-height desk, and a Herman Miller chair that still had the tags attached. The first time I’d met him, at an economics conference, he had told me he was one of several cousins on his mother’s side who go by Raj, all named after their grandfather, Nadarajan, all with sharp minds and the same long legs and easy gait. Yet of Nadarajan’s children, only Chetty’s mother graduated from college, and he’s certain that this fact shaped his generation’s possibilities. He was able to come to the United States as a child and attend an elite private school, the University School of Milwaukee. New York Raj—the family appends a location to keep them straight—came to the U.S. later in life, at age 28, worked in drugstores, and then took a series of jobs with the City of New York. Singapore Raj found a job in a temple there that allows him to support his family back in India, but means they must live apart. Karaikudi Raj, named for the town where his mother grew up, committed suicide as a teenager.

“We are not trying to do something that is unimaginable or has never happened,” Chetty told me. “It happens just down the road.”
I asked Boston Raj to consider what might have become of him if that wealthy Indian businessman had not decided, in the precise year his mother was finishing high school, to create a college for the talented women of southeastern Tamil Nadu. “I would likely not be here,” he said, thinking for a moment. “To put it another way: Who are all the people who are not here, who would have been here if they’d had the opportunities? That is a really good question.”

Charlotte is one of America’s great urban success stories. In the 1970s, it was a modest-size city left behind as the textile industry that had defined North Carolina moved overseas. But in the 1980s, the “Queen City” began to lift itself up. US Airways established a hub at the Charlotte Douglas International Airport, and the region became a major transportation and distribution center. Bank of America built its headquarters there, and today Charlotte is in a dead heat with San Francisco to be the nation’s second-largest banking center, after New York. New skyscrapers have sprouted downtown, and the city boundary has been expanding, replacing farmland with spacious homes and Whole Foods stores. In the past four decades, Charlotte’s population has nearly tripled.

Charlotte has also stood out in Chetty’s research, though not in a good way. In a 2014 analysis of the country’s 50 largest metropolitan areas, Charlotte ranked last in ability to lift up poor children. Only 4.4 percent of Charlotte’s kids moved from the bottom quintile of household income to the top. Kids born into low-income families earned just $26,000 a year, on average, as adults—perched on the poverty line. “It was shocking,” says Brian Collier, an executive vice president of the Foundation for the Carolinas, which is working with Opportunity Insights. “The Charlotte story is that we are a meritocracy, that if you come here and are smart and motivated, you will have every opportunity to achieve greatness.” The city’s true story, Chetty’s data showed, is of selective opportunity: All the data-scientist and business-development-analyst jobs in the thriving banking sector are a boon for out-of-towners and the progeny of the well-to-do, but to grow up poor in Charlotte is largely to remain poor.

To help cities like Charlotte, Chetty takes inspiration from medicine. For thousands of years, he explained, little progress was made in understanding disease, until technologies like the microscope gave scientists novel ways to understand biology, and thus the pathologies that make people ill. In October, Chetty’s institute released an interactive map of the United States called the Opportunity Atlas, revealing the terrain of opportunity down to the level of individual neighborhoods. This, he says, will be his microscope.

Drawing on anonymized government data over a three-decade span, the researchers linked children to the parents who claimed them as dependents. The atlas then followed poor kids from every census tract in the country, showing how much they went on to earn as adults. The colors on the atlas reveal a generation’s prospects: red for areas where kids fared the worst; shades of orange, yellow, and green for middling locales; and blue for spots like Salt Lake City’s Foothill neighborhood, where upward mobility is strongest. It can also track children born into higher income brackets, compare results by race and gender, and zoom out to show states, regions, or the country as a whole.

The Opportunity Atlas has a fractal quality. Some regions of the United States look better than high-mobility countries such as Denmark, while others look more like a developing country. The Great Plains unfurl as a sea of blue, and then the eye is caught by an island of red—a mark of the miseries inflicted on the Oglala Lakota by European settlers. These stark differences recapitulate themselves on smaller and smaller scales as you zoom in. It’s common to see opposite extremes of opportunity within easy walking distance of each other, even in two neighborhoods that long-term residents would consider quite similar.

To find a cure for what ails America, Chetty will need to understand all of this wild variation. Which factors foster opportunity, and which impede it? The next step will be to find local interventions that can address these factors—and to prove, with experimental trials, that the interventions work. The end goal is the social equivalent of precision medicine: a method for diagnosing the particular weaknesses of a place and prescribing a set of treatments. This could transform neighborhoods, and restore the American dream from the ground up.

If all of this seems impossibly ambitious, Chetty’s counterargument is to point to how the blue is marbled in with the red. “We are not trying to do something that is unimaginable or has never happened,” he told me over lunch one day. “It happens just down the road.”

Yet in Charlotte, where Opportunity Insights hopes to build its proof of concept, the atlas reveals swaths of bleak uniformity. Looking at the city, you first see a large bluish wedge south of downtown, with Providence Road on one side and South Boulevard on the other, encompassing the mostly white, mostly affluent areas where children generally grow up to do well. Surrounding the wedge is a broad expanse in hues of red that locals call “the crescent,” made up of predominantly black neighborhoods where the prospects for poor children are pretty miserable. Hunger and homelessness are common, and in some places only one in five high-school students scores “proficient” on standardized tests. In many parts of the crescent, the question isn’t What’s holding kids back? so much as What isn’t holding them back? It’s hard to know where to start.

The most significant challenge Chetty faces is the force of history. In the 1930s, redlining prevented black families from buying homes in Charlotte’s more desirable neighborhoods. In the 1940s, the city built Independence Boulevard, a four-lane highway that cut through the heart of its Brooklyn neighborhood, dividing and displacing a thriving working-class black community. The damage continued in the ’60s and ’70s with new interstates. It’s common to hear that something has gone wrong in parts of Charlotte, but the more honest reading is that Charlotte is working as it was designed to. American cities are the way they are, and remain the way they are, because of choices they have made and continue to make.

Does a professor from Harvard, even one as influential and well funded as Chetty, truly stand any chance of bending the American story line? On his national atlas, the most obvious feature is an ugly red gash that starts in Virginia, curls down through the Southeast’s coastal states—North Carolina, South Carolina, Georgia, and Alabama—then marches west toward the Mississippi River, where it turns northward before petering out in western Tennessee. When I saw this, I was reminded of another map: one President Abraham Lincoln consulted in 1861, demarcating the counties with the most slaves. The two maps are remarkably similar. Set the documents side by side, and it may be hard to believe that they are separated in time by more than a century and a half, or that one is a rough census of men and women kept in bondage at the time of the Civil War, and the other is a computer-generated glimpse of our children’s future.


Top: A map consulted by President Lincoln in 1861, demarcating the counties with the most slaves. (Library of Congress)

Bottom: A detail from Chetty’s Opportunity Atlas, in which areas with poor upward mobility are shown in red. The similarities between the two documents suggest that it will be difficult for Chetty to change the landscape of opportunity. (Opportunity Insights / U.S. Census Bureau)
In 2003, after earning his doctorate, Chetty moved to UC Berkeley for his first job. He was, at the time, the only person in his immediate family—his parents and two older sisters, both biomedical researchers—who had not published a paper. Education was highly prized. He was taught that it would be sacrilege to ever step on a book. When he visits his parents at their home, north of Boston, his mother still makes him a favorite dish with bhindi (Hindi for “okra”), which, she told me, is supposed to be good for the brain.

Both of Chetty’s parents descend from the Chettiar caste, a mercantile group historically involved in banking, and the kids were raised to carry on their cultural heritage. They learned Tamil in addition to Hindi. Chetty’s sisters married men with Chettiar backgrounds. Chetty rejects the caste system, though he first met his wife, Sundari, after one of his sisters got to know her through the Chettiar community. (Sundari is a stem-cell biologist.)

Chetty had always been drawn to public economics—the study of government policy and how it might be improved. And, as it happened, he was embarking on his career as a revolution in the field was under way. In the past, economists had to rely heavily on surveys, but the advent of cheap, powerful computing allowed for a new kind of economics—one that drew on the extensive administrative data gathered by governments. Survey participants number in the hundreds or thousands; administrative data can yield records in the hundreds of millions.

In November 2007, Chetty came across an ad from the IRS seeking help organizing its electronic files into a format that would be easier to use for research. He immediately recognized that completing the job would make it possible for scholars to go far deeper into tax data. He and John Friedman began the process of registering to be federal contractors—which involved, among other things, certifying that their workplace met federal safety standards, and calling on Friedman’s brother, who lived in Washington, D.C., to take a cab out to Maryland to hand-deliver their application materials, in triplicate.

Like many good ideas, the project seems obvious in retrospect, but the truth is that nobody could have known how useful the data would prove to be—and it worked only because Chetty and his colleagues have an almost superhuman degree of patience.

Nathaniel Hendren, who has known Chetty for seven years, told me he’s never seen Chetty happier than one Friday evening in the summer of 2014, when they were sitting in some IRS cubicles at the John F. Kennedy Federal Building in downtown Boston. (The only way to access the government’s data was inside a federal building, on secure servers, with the computers logging their requests.) That night, Chetty and Hendren were wrestling with thousands of lines of code designed to pull together responses scattered across hundreds of millions of 1040s, W2s, and other forms (taxpayer names are kept separate to protect privacy), while ensuring that nothing in the code introduced errors or subtle biases. At some point, Hendren recalled, he heard Chetty yell “Sweet!” Hendren looked over and Chetty, smiling, explained that his flight out of Logan airport that night had just been delayed: more time to work.

Over the past two decades, economists have tried to structure their work, as much as possible, to resemble scientific experiments. This “credibility revolution” is an attempt to explicitly link causes to effects, and sweep aside the old criticism that correlation is not the same as causation. One of the advantages of the large tax database Chetty and his colleagues constructed is that it allows “quasi-experiments”—clever statistical methods that approach the power of a true experiment without requiring a researcher to, say, randomly assign children to live in different cities.

For example, Chetty and Hendren looked at children who changed cities. They found that the later a child moved to a higher-opportunity area, the less effect the move seemed to have on future earnings. But they also devised additional tests to ensure that the effect was causal, such as looking at siblings who moved at the same time: a quasi-experiment in which two children grew up in the same family, but were exposed to a new area for a shorter or longer period depending on their age at the time of the move. The result was a highly credible conclusion, based on millions of data points, that moving a child to a better neighborhood boosts his or her future income—and the younger the child, the greater the benefit.

There was, however, a significant problem: Their conclusion contradicted one of the most influential poverty experiments of recent decades. In the 1990s, the federal government launched Moving to Opportunity, a program designed to relocate families living in public housing to safer neighborhoods, where they had access to better jobs and schools. Thousands of families in five cities were randomly selected to receive housing vouchers and support services to help them move to lower-poverty areas. After a decade of study, researchers concluded that while these “mover” families experienced some physical and mental-health benefits, test scores among the kids didn’t rise, and there were no signs of financial benefit for adults or older children.

In 2014, Chetty, Hendren, and the Harvard economist Lawrence Katz asked the IRS and the Department of Housing and Urban Development, which had overseen the program, for permission to take another look at what had happened to the children. When the earlier follow-up had been done, the youngest kids, who had moved before they were teenagers, had not yet reached their earning years, and this turned out to make all the difference. This young group of movers, the economists found, had gone on to earn 31 percent more than those who hadn’t moved, and 4 percent more of them attended college. They calculated that for an 8-year-old child, the value of the extra future earnings over a lifetime was almost $100,000, a substantial sum for a poor family. For a family with two children, the taxes paid on the extra income more than covered the costs of the program. “The big insight,” Kathryn Edin, a sociology professor at Princeton, told me, “is that it took a generation for the effects to manifest.”

Last july, I took a tour of Charlotte with David Williams, the 34-year-old policy director of Opportunity Insights and the man responsible for translating Chetty’s research into action on the ground. Williams and members of his team crammed into the back of a white Ford Explorer with color printouts of various Charlotte neighborhoods as they appear on the atlas. Brian Collier, of the Foundation for the Carolinas, sat in the front seat, serving as a guide.

As the driver headed northeast, the high-rises of “Uptown” shifted abruptly to low-slung buildings and chain-link fences. Collier pointed out a men’s shelter in the rapidly gentrifying neighborhood of Lockwood, where he’d recently seen a drug deal go down a block away from a house that had sold for half a million dollars.

We continued on to Brightwalk, a new mixed-income development with long rows of townhomes, before turning west for a loop around West Charlotte High School, a once-lauded model of successful integration. In the 1990s, though, support for busing waned, and in 1999, a judge declared that race could not be used as a factor in school assignment. Now the student population is virtually all minority and overwhelmingly poor, and the surrounding neighborhood is deep red on the atlas. The homes are neat, one-story single families, a tad rough around the edges but nothing like the burnt-out buildings in Detroit, where Williams previously worked on economic development for the mayor. “It reminds you how hard it is to tell where real opportunity is,” Williams said. “You can’t just see it.”

Opportunity is not the same as affluence. Consider a kid who grows up in a household earning about $27,000 annually, right at the 25th percentile nationally. In Beverly Woods, a relatively wealthy, mostly white enclave in South Charlotte with spacious, well-kept yards, he could expect his household income to be $42,900 by age 35. Yet in Huntersville, an attractive northern suburb with nearly the same average household income as Beverly Woods, a similar kid could expect only $24,800—a stark difference, invisible to a passing driver.

This dynamic also functions in poorer areas. For a child in Reid Park, an African American neighborhood on the west side of Charlotte, near the airport—a place that has struggled to recover from a crime epidemic in the 1980s—the expected household income at age 35 is a dismal $17,800, on average. But in East Forest, a white, working-class neighborhood in southeast Charlotte, the expected future income jumps to $32,600.

There are places like East Forest in cities around the country. Chetty and his team have taken to calling them “opportunity bargains”: places with relatively affordable rents that punch above their weight with respect to opportunity. He doesn’t yet know why some places are opportunity bargains, but he considers the discovery of these neighborhoods to be a breakthrough. John Friedman told me that if the government had been able to move families to opportunity-bargain neighborhoods in the original Moving to Opportunity experiment—places selected for higher opportunity, not lower poverty—the children’s earnings improvements would have been more than twice as great.

In the crimson sectors of Chetty’s atlas, the problem is both the absence of opportunity and the presence of its opposite: swift currents that can drag a person down.
Chetty’s team has already begun to apply this concept in another of its partner cities, Seattle, working with two local housing authorities to navigate the thorny process of translating research into measurable social change. It’s hard for poor families to manage an expansive housing search, which requires time, transportation, and decent credit. The group created a program with “housing navigators,” who point participants toward areas with relatively high opportunity, help with credit-related issues, and even give neighborhood tours. Landlords need encouragement as well. They can be wary of tenants bearing vouchers, which mean government oversight and paperwork. The Seattle program has streamlined this process, and offers free damage insurance to sweeten the deal.

Tenants have just started moving, but the program is already successful: The majority of families who received assistance moved to high-opportunity areas, compared with one-fifth for the control group, which was not provided with the extra services. Chetty estimates that the program will increase each child’s lifetime earnings by $88,000. In February, President Donald Trump signed into law a bill that provides $28 million to try similar experimental programs in other locations. The bill enjoyed overwhelming bipartisan support, and this spring Chetty was invited to brief the Department of Housing and Urban Development. He told me he’s hopeful that the program can be expanded to the 2.2 million families that receive HUD housing vouchers every year. “Then you’d actually be doing something about poverty in the American city,” he said. “What I like about this is it’s not some pie-in-the-sky thing. We have something that works.”

Charlotte is among the cities interested in implementing the Seattle strategy, but officials also want to use the atlas to select better building sites for affordable housing. In the past, much of the city’s affordable housing was constructed in what Chetty’s data reveal to be high-poverty, low-opportunity areas. “Let’s not just think about building X units of new affordable housing,” Williams said. “Let’s really leverage housing policy as part of a larger economic-mobility agenda for the community.”

Opportunity bargains, however, are not an inexhaustible resource. The crucial question, says the Berkeley economist Enrico Moretti, is whether the opportunity in these places derives from “rival goods”—institutions, such as schools, with limited capacity—or “non-rival goods,” such as local culture, which are harder to deplete. When new people move in, what happens to opportunity? And even if an influx of families doesn’t disrupt the opportunity magic, people aren’t always eager to pick up and leave their homes. Moving breaks ties with family, friends, schools, churches, and other organizations. “The real conundrum is how to address the larger structural realities of inequality,” says the Harvard sociologist Robert Sampson, “and not just try to move people around.”

For all he’s learned about where opportunity resides in America, Chetty knows surprisingly little about what makes one place better than another. He and Hendren have gathered a range of social-science data sets and looked for correlations to the atlas. The high-opportunity places, they’ve found, tend to share five qualities: good schools, greater levels of social cohesion, many two-parent families, low levels of income inequality, and little residential segregation, by either class or race. The list is suggestive, but hard to interpret.

For example, the strongest correlation is the number of intact families. The explanation seems obvious: A second parent usually means higher family income as well as more stability, a broader social network, additional emotional support, and many other intangibles. Yet children’s upward mobility was strongly correlated with two-parent families only in the neighborhood, not necessarily in their home. There are so many things the data might be trying to say. Maybe fathers in a neighborhood serve as mentors and role models? Or maybe there is no causal connection at all. Perhaps, for example, places with strong church communities help kids while also fostering strong marriages. The same kinds of questions flow from every correlation; each one may mean many things. What is cause, what is effect, and what are we missing? Chetty’s microscope has revealed a new world, but not what animates it—or how to change it.

Chetty has found that opportunity does not correlate with many traditional economic measures, such as employment or wage growth. In the search for opportunity’s cause, he is instead focusing on an idea borrowed from sociology: social capital. The term refers broadly to the set of connections that ease a person’s way through the world, providing support and inspiration and opening doors.


Chetty believes that if upward mobility can be measured with enough precision, it can be understood. “The big-picture goal,” he told me, “is to revive the American dream.” (​Carlos Chavarría)
Economics has long played the role of sociology’s annoying older brother—conventionally accomplished and wholeheartedly confident, unaware of what he doesn’t know, while still commanding everyone’s attention. Chetty, though, is part of a younger generation of scholars who have embraced a style of quantitative social science that crosses old disciplinary lines. There are strong hints in his research that social capital and mobility are intimately connected; even a crude measure of social capital, such as the number of bowling alleys in a neighborhood, seems to track with opportunity. His data also suggest that who you know growing up can have lasting effects. A paper on patents he co-authored found that young women were more likely to become inventors if they’d moved as children to places where many female inventors lived. (The number of male inventors had little effect.) Even which fields inventors worked in was heavily influenced by what was being invented around them as children. Those who grew up in the Bay Area had some of the highest rates of patenting in computers and related fields, while those who spent their childhood in Minneapolis, home of many medical-device manufacturers, tended to invent drugs and medical devices.* Chetty is currently working with data from Facebook and other social-media platforms to quantify the links between opportunity and our social networks.

Sociologists embrace many ways of understanding the world. They shadow people and move into communities, wondering what they might find out. They collect data and do quantitative analysis and read economics papers, but their work is also informed by psychology and cultural studies. “When you are released from the harsh demands of experiment, you are allowed to make new discoveries and think more freely about what is going on,” says David Grusky, a Stanford sociology professor who collaborates with Chetty. I asked Princeton’s Edin what she thought would end up being the one thing that best explains the peaks and valleys of American opportunity. She said her best guess is “some kind of social glue”—the ties that bind people, fostered by well-functioning institutions, whether they are mosques or neighborhood soccer leagues. The staff at Opportunity Insights has learned: When an economist gets lost, a sociologist can touch his elbow and say, You know, I’ve been noticing some things.

In charlotte, Chetty still aspires to practice “precision medicine,” but he told me his initial goal is more modest: to see whether he and his team can find anything that helps. Opportunity Insights is planning housing and higher-education initiatives, but social capital is at the center of its approach. It is working with a local organization called Leading on Opportunity, and looking at nonprofits that are already operating successfully, including Communities in Schools, a national group that provides comprehensive student support, as well as a job-training program called Year Up. Chetty is also using tax data to measure the long-term impacts of dozens of place-based interventions, such as enterprise zones, which use tax and other incentives to draw businesses into economically depressed areas. (He expects to see initial results from these analyses later this year.) Chetty may not have many answers yet, but he is convinced that this combination of data, collaboration, and fieldwork will make it possible to move from educated guesses to tailored prescriptions. “There are points when the pieces come together,” Chetty told me. “My instinct is that in social science, this generation is when that is going to happen.”

Chetty’s pitch to the nation is that our problems have technocratic solutions, but at times I sense that he is avoiding an argument. Surely our neighborhoods can be improved, and those improvements can help the next generation achieve better outcomes. But what of the larger forces driving the enormous disparities in American wealth? Poor people would be better off if their children had better prospects, but also if they had more money—if the fruits of our society were shared more broadly. “I can take money from you and give it to me, and maybe that is good and maybe it is not,” he said. “I feel like there are a lot of people working on redistribution, and it is hard to figure out the right answer there.” To focus on the question of who gets what is also, of course, politically incendiary.

Chetty believes there is more progress to be made through a moral framing that is less partisan. “There are so many kids out there who could be doing so many great things, both for themselves and for the world,” he said. Chetty’s challenge to the system is measured and empirical; it’s one that billionaires and corporations can happily endorse. But his stance is also a simple matter of personality: Chetty is no agitator. He told me, “I like to find solutions that please everyone in the room, and this definitely has that feel.”

In Charlotte, even the circumscribed version of social change that Chetty is attempting looks daunting. Last summer, before the Opportunity Insights team came to town, I drove around to the back of West Charlotte High School, to a hamlet of pale-yellow temporary-classroom buildings, each set on concrete blocks. One building has been given over to Eliminate the Digital Divide, known as E2D, a nonprofit that takes donations of old laptops, then refurbishes and distributes them for $60 apiece to students who have no computer of their own. According to E2D, half of the county’s public-school students have been unable to complete a homework assignment because they don’t have access to a computer or the internet.

Inside the E2D building is a bright room ringed by a series of workstations where West Charlotte student-employees inspect laptops, set up hard drives, and test the final products. Whiteboards, photos, and posters with inspirational phrases like college bound! cover the walls. By the door, a pair of yellow couches serve as a waiting area. When the boys get their computers, they work hard to suppress a smile, whereas the girls are prone to let loose. Sometimes they jump up and down, and sometimes they cry.

I met Kalijah Jones, a young black woman in a pale-pink sleeveless blouse and matching skirt. She had started working at E2D during her senior year, in 2017. Not long into our conversation, she said, “I love my life!”—this despite the fact that she was living in a homeless shelter at the time.

For Jones, the biggest benefit brought by E2D was not the computer or the job, but the social capital the program provided. Last year, she said, E2D’s West Charlotte lab was recognized with a local technology award, and the founder invited Jones and some of her co-workers to join him for the awards ceremony at the Knight Theater, where the Charlotte Ballet performs. One of the other honorees was Road to Hire, a program that pays high-school graduates as it trains them for jobs in sales and tech. The head of Road to Hire was at the ceremony, and he gave Jones a business card, which led to a paid spot in the program’s training program.

But in the crimson sectors of Chetty’s atlas, the problem is both the absence of opportunity and the presence of its opposite: swift currents that can drag a person down. There are, in these places, a few narrow paths to success, and 99 ways to falter. Jones made it through high school despite living in a shelter, and was accepted to Western Carolina University with financial aid. But she decided not to go, in part because she couldn’t imagine leaving her struggling mother and sister behind to live on a campus three hours away. Last winter, the three of them left Charlotte, and the prospects that were beginning to open up for Jones there, and moved to New Jersey, where she grew up. When I last spoke with her, she’d found work at an Amazon warehouse.

One friday evening, I was in Chetty’s Stanford office when a ballerina arrived. Sanvi, Chetty’s 3-year-old daughter, wore a pink tutu with matching hair ribbons and tights. She declined—vigorously—the white sweater offered to ward off the evening chill. Chetty and I had spent hours discussing his research, but when the nanny dropped Sanvi off, it marked the end of the day. Chetty gathered his things and whisked her up in his arms. “Hold me properly, Appa,” Sanvi admonished. Outside, we got into Chetty’s aging silver Acura and headed to an Indonesian restaurant for takeout. Sanvi bubbled with enthusiasm. “I want to be a fairy princess,” she announced from the back seat. “Can I be a fairy princess?” Chetty glanced in the rearview mirror and assured Sanvi that when she grows up, she can be whatever she wants.

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After stopping for the food, we pulled up to a light-brown ranch house, with beautiful plantings out front. Inside, the house was clearly Sanvi’s. Taking a seat in the open kitchen, I was surrounded by a tapestry of exuberant finger paintings taped to the walls, interspersed with pages neatly torn from coloring books (penguins, parrots, bunnies, each splashed with color). A pair of persimmon trees were fruiting out back.

Chetty told me that his interest in poverty dates back to the horrifying want he observed on the streets of New Delhi. But only when he built the first version of his atlas did he see what he should do about it. “I realized,” he said, “we could have the biggest impact on poverty by focusing on children.”

Chetty thinks about revolution like an economist does: as a compounding accumulation of marginal changes. Bump the interest rate on your savings account by one notch, and 30 years later, your balance is much improved. Move a family to a better zip code, or foster the right conditions in that family’s current neighborhood, and their children will do better; do that a thousand times, or ten thousand, and the American dream can be more possible, for more people, than it is today.

In the 1930s, the poet Langston Hughes published what remains one of the most honest descriptions of that dream:

A dream so strong, so brave, so true
That even yet its mighty daring sings
In every brick and stone, in every furrow turned
That’s made America the land it has become
The poem, though, is laced with a counterpoint of protest: “America was never America to me”—not to the “man who never got ahead”; “the poorest worker bartered through the years”; or “the Negro, servant to you all.” Still, for all its outrage, the poem ends with a paradoxical yearning: “O, let America be America again,” Hughes wrote. “The land that never has been yet.”

Hearing stories of the American dream as a boy in New Delhi, Chetty adopted the faith. When he became a scientist, he discerned the truth. What remains is contradiction: We must believe in the dream and we must accept that it is false—then, perhaps, we will be capable of building a land where it will yet be true.

This article appears in the August 2019 print edition with the headline “Raj Chetty’s American Dream.”

* This article originally stated that Minneapolis was the home of the Mayo Clinic.

Gareth Cook is a Pulitzer Prize–winning journalist and a contributing writer at The New York Times Magazine.



商业
将修复美国梦的经济学家
没有人比拉吉-切蒂(Raj Chetty)在破除社会流动的神话方面做得更多。但他有一个使机会平等成为现实的计划。

作者：加雷斯-库克
2019年8月号
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更新于美国东部时间2019年7月17日下午3:47。

拉吉-切蒂在他的人生开始之前就得到了最大的突破。他的母亲安布在泰米尔纳德邦长大，这是一个位于印度次大陆南端的热带州。安布在她的五个兄弟姐妹中表现出最大的学术潜力，但她的未来却受到习俗的限制。虽然安布的父亲鼓励她的学术倾向，但该地区没有大学，把女儿送出去接受教育是不体面的。

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但在安布接近高中毕业时，一个小小的奇迹改变了她的生活。一个当地的大亨，自己也是一个聪明女儿的父亲，决定在他优雅的住宅里开办一所女子学院。安布被录取到由30名年轻女性组成的首期班级，在茅草屋顶下宽敞的院子里学习英语，并在清晨乘车前往附近的大学进行化学实验或在男人到来之前解剖青蛙的心脏。安布成绩优异，于是开始了快速的上升通道。她报考了医学院。"有人问她父亲，"为什么你要送她去那里？" 在他们的Chettiar种姓中，丈夫通常在国外工作数年，把钱寄回来，而妻子则被留下来抚养孩子。医学学位对一个呆在家里的母亲有什么用呢？

1962年，安布嫁给了维拉帕-切蒂，一个来自泰米尔纳德邦的聪明人，他的母亲和祖母有时会少吃点东西，以便为他提供更多食物。安布成为一名医生，并在丈夫获得经济学博士学位时支持他。到1979年，当拉吉在新德里出生时，他的母亲是一名儿科教授，他的父亲是一名经济学教授，曾担任过英迪拉-甘地总理的顾问。

切蒂9岁时，他的家人搬到了美国，他开始了几乎和他父母一样戏剧性的攀登。他是高中班级的告别演说者，然后仅用三年时间就从哈佛大学毕业，在那里他获得了经济学博士学位，并在28岁时成为该大学历史上最年轻的获得终身职位的教员之一。2012年，他被授予麦克阿瑟天才奖。次年，他被授予约翰-贝茨-克拉克奖章，该奖章授予40岁以下最有前途的经济学家。(当时他33岁。) 2015年，斯坦福大学将他聘走。去年夏天，哈佛大学将他吸引回来，在比尔及梅林达-盖茨基金会和陈扎克伯格倡议的资助下，成立了自己的研究和政策研究所。

切蒂这个月就40岁了，他被广泛认为是他那一代人中最有影响力的社会科学家之一。"哈佛大学的爱德华-格莱泽（Edward Glaeser）说："拉吉的问题不是他是否会获得诺贝尔奖，而是何时获得。"

为切蒂带来如此名声的工作是对其家族历史的回应。他开创了一种方法，利用新的政府数据来源来显示美国家庭的跨代情况，揭示了惊人的向上流动和停滞的模式。在一项早期研究中，他表明，1940年出生的孩子有90%的机会比他们的父母挣得更多，但对于40年后出生的孩子来说，这种机会已经下降到50%，就像抛硬币一样。

2013年，切蒂发布了一张彩色的美国地图，显示了人们的财务前景在多大程度上取决于他们碰巧在哪里长大，令人惊讶。在盐湖城，一个出生在家庭收入最低的五分之一家庭的人，有10.8%的机会达到最高的五分之一。在密尔沃基，这一几率还不到一半。


切蒂9岁时。他后来成为高中的告别演说者，并获得了哈佛大学的本科学位和经济学博士学位。28岁时，他是该大学历史上最年轻的获得终身教职的教师之一。(Raj Chetty提供)
从那时起，他的每项研究都成为头版媒体事件（一位合作者称之为 "切蒂炸弹"），将敬畏--数以百万计的数据点、生动的信息图表、全国性的镜头--与震惊结合起来。统计数据证明，这可能不是你愿意想象的美国，但这是我们允许美国变成的样子。全国数十所精英大学中，1%的孩子比来自家庭收入最低的60%的家庭的孩子多。一个出生在富裕家庭的黑人男孩最终沦为穷人的可能性是来自富裕家庭的白人男孩的两倍以上。切蒂已经将大数据确立为美国辩论中的一种道德力量。

现在他想做的不仅仅是改变我们对美国的理解，他想改变美国本身。他在哈佛大学新成立的研究所名为 "机遇洞察"，其明确目标是在全国各地的城市应用他的研究结果，并证明社会科学家，尽管有令人沮丧的记录，但能够解决他们在期刊上阐述的问题。他的员工包括一个八人的政策团队，该团队正在与夏洛特、西雅图、底特律、明尼阿波利斯和其他城市建立伙伴关系。

对于一个为记录国家的失败做了这么多工作的人来说，切蒂是奇怪的乐观的。他有科学家的自信。如果像向上流动这样的现象可以被足够精确地测量，那么它就可以被理解；如果它可以被理解，那么它就可以被操纵。"Chetty告诉我，"大的目标是恢复美国梦"。

去年夏天，我在Opportunity Insights的开幕日参观了它。办公室设在一栋砖混建筑的二楼，在一家咖啡馆的上方，与哈佛大学的柱状维德纳图书馆隔着马萨诸塞州大道。Chetty穿着经济休闲装来到这里：淡紫色礼服衬衫，没有夹克，黑色休闲裤。他身材高大修长，气质不凡；他微笑着迎接他的两位长期合作者--布朗大学经济学家约翰-弗里德曼和哈佛大学的纳撒尼尔-亨德伦。他们带着他四处参观，展示了完成的空间，用白色、木头和铝的现代调色板做的，有黄色和鼠尾草的重点墙。

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后来，在Chetty和他的同事为新员工举办了一天的研讨会之后，我在他的办公室里找到了他，办公室里有一块纯净的白板，一张可调节高度的桌子，以及一把还贴着标签的赫曼米勒椅子。我第一次见到他时，是在一个经济学会议上，他告诉我，他是他母亲那边的几个表兄弟之一，他们都叫Raj，都是以他们的祖父Nadarajan命名的，都有敏锐的头脑和同样的长腿和轻松的步伐。然而，在纳达拉詹的孩子中，只有切蒂的母亲从大学毕业，他确信这一事实塑造了他这一代人的可能性。他从小就能来到美国，在精英私立学校--密尔沃基大学学校上学。纽约拉吉--这个家庭附加了一个地点以保持他们的连续性--在生命的后期，28岁时来到美国，在药店工作，然后在纽约市做了一系列工作。新加坡拉吉在那里的一座寺庙里找到了一份工作，这使他能够支持他在印度的家人，但意味着他们必须分开居住。卡莱库迪-拉吉因其母亲成长的小镇而得名，十几岁时就自杀了。

"我们并不是要做一些难以想象或从未发生过的事情，"切蒂告诉我。"它就发生在路上。"
我让波士顿-拉吉考虑一下，如果那位富有的印度商人没有在他母亲完成高中学业的那一年决定为泰米尔纳德邦东南部的天才女性创建一所大学，他可能会变成什么样。"我很可能不会在这里，"他说，思考了一会儿。"换个角度来说。所有不在这里的人是谁，如果他们有机会，他们会在这里？这真是一个好问题。"

夏洛特是美国伟大的城市成功故事之一。在20世纪70年代，它是一个规模不大的城市，因为曾经定义了北卡罗来纳州的纺织业转移到了海外。但在20世纪80年代，"皇后城 "开始提升自己。美国航空公司在夏洛特道格拉斯国际机场建立了一个枢纽，该地区成为一个主要的运输和分销中心。美国银行在这里建立了总部，今天，夏洛特与旧金山并驾齐驱，成为美国第二大银行中心，仅次于纽约。新的摩天大楼在市中心拔地而起，城市边界也在不断扩大，用宽敞的住宅和全食超市取代了农田。在过去的四十年里，夏洛特的人口增长了近两倍。

在切蒂的研究中，夏洛特也很突出，尽管不是好的方面。在2014年对全国50个最大都市区的分析中，夏洛特在提升贫困儿童的能力方面排名最后。只有4.4%的夏洛特儿童从家庭收入最低的五分之一人口中升至最高。出生在低收入家庭的孩子，成年后平均每年只赚26,000美元--在贫困线上徘徊。"与Opportunity Insights合作的卡罗莱纳州基金会的执行副总裁布莱恩-科利尔说："这令人震惊。"夏洛特的故事是，我们是一个任人唯贤的地方，如果你来到这里，并且聪明和有动力，你将有一切机会实现伟大的目标。" Chetty的数据显示，这个城市的真实故事是有选择的机会。在繁荣的银行业中，所有的数据科学家和商业发展分析师的工作对外地人和富人的后代来说是一个福音，但在夏洛特长大的穷人在很大程度上会继续贫穷。

为了帮助像夏洛特这样的城市，Chetty从医学中获得了灵感。他解释说，几千年来，在了解疾病方面几乎没有进展，直到像显微镜这样的技术给了科学家了解生物学的新方法，从而了解使人生病的病理。10月，Chetty的研究所发布了一张名为 "机会图集 "的美国互动地图，揭示了机会的地形，直至个别社区的水平。他说，这将是他的显微镜。

研究人员利用三十年间的匿名政府数据，将儿童与声称他们是受抚养人的父母联系起来。然后，地图集跟踪了全国每个人口普查区的贫困儿童，显示他们成年后的收入情况。地图上的颜色显示了一代人的前景：红色代表孩子们表现最差的地区；橙色、黄色和绿色代表中等水平的地区；蓝色代表盐湖城的山麓社区，那里的上升流动性最强。它还可以追踪出生在高收入阶层的儿童，按种族和性别比较结果，并放大显示各州、地区或整个国家。

机会图集有一种分形的特点。美国的一些地区看起来比丹麦这样的高流动性国家更好，而其他地区看起来更像一个发展中国家。大平原是一片蓝色的海洋，然后人们的目光被一个红色的岛屿所吸引--这是欧洲定居者对奥格拉拉-拉科塔人造成的痛苦的标志。当你放大时，这些鲜明的差异会在越来越小的范围内重现出来。常见的情况是，在步行距离内就能看到机会的两个极端，甚至在两个长期居民认为相当相似的社区。

为了找到治疗美国病症的方法，切蒂需要了解所有这些疯狂的变化。哪些因素促进了机会，哪些因素阻碍了机会？下一步将是找到能够解决这些因素的当地干预措施，并通过实验证明这些干预措施的有效性。最终的目标是相当于精准医疗的社会手段：一种诊断一个地方的特殊弱点并开出一套治疗方案的方法。这可以改变社区，并从根本上恢复美国梦。

如果这一切看起来不可能有雄心壮志，切蒂的反驳是指出蓝色是如何与红色相搭配的。"我们并不是要做一些难以想象或从未发生过的事情，"有一天他在午餐时告诉我。"它就发生在路上。"

然而，在夏洛特，也就是Opportunity Insights希望建立其概念证明的地方，地图集显示了成片的暗淡的统一性。纵观这座城市，你首先看到的是市中心以南的一个巨大的蓝色楔子，一边是普罗维登斯路，另一边是南大道，包括了大部分白人、大部分富裕地区，这些地区的孩子一般都能长大成人。围绕着这个楔子的是一片广阔的红色区域，当地人称之为 "新月形"，由以黑人为主的社区组成，那里的贫困儿童的前景相当悲惨。饥饿和无家可归的情况很普遍，在一些地方，只有五分之一的高中生在标准化测试中获得 "优秀 "的成绩。在新月形地区的许多地方，问题不是什么阻碍了孩子，而是什么没有阻碍他们？我们很难知道从哪里开始。

切蒂面临的最重大挑战是历史的力量。在20世纪30年代，划定红线的做法使黑人家庭无法在夏洛特更理想的社区购买房屋。20世纪40年代，该市建造了独立大道，这是一条四车道的高速公路，穿过了布鲁克林区的中心地带，分割和取代了一个繁荣的工人阶级黑人社区。这种破坏在60年代和70年代随着新的高速公路的出现而继续。人们经常听到有人说夏洛特的部分地区出了问题，但更诚实的解读是，夏洛特正在按照设计的方式运作。美国的城市之所以成为现在这样，并保持现在这样，是因为他们已经做出并将继续做出选择。

一个来自哈佛的教授，即使是像切蒂这样有影响力和资金充足的教授，是否真的有机会改变美国的故事线？在他的国家地图上，最明显的特征是一个丑陋的红色裂口，从弗吉尼亚州开始，沿着东南沿海各州--北卡罗来纳州、南卡罗来纳州、佐治亚州和阿拉巴马州--然后向西行进到密西西比河，在那里转向北方，然后在田纳西州西部逐渐消失。当我看到这幅地图时，我想起了另一幅地图：亚伯拉罕-林肯总统在1861年参考的地图，划定了拥有最多奴隶的县份。这两张地图非常相似。把这两份文件并排放在一起，你可能很难相信它们在时间上相隔了一个半世纪，或者说一个是对内战时被奴役的男人和女人的粗略普查，而另一个是计算机生成的对我们孩子的未来的一瞥。


上图：1861年林肯总统参考的地图，划定了拥有最多奴隶的县。(美国国会图书馆)

底部。切蒂的《机会图集》中的一个细节，其中向上流动能力差的地区用红色表示。这两份文件之间的相似性表明，切蒂很难改变机会的面貌。(Opportunity Insights / U.S. Census Bureau)
2003年，在获得博士学位后，切蒂来到加州大学伯克利分校开始了他的第一份工作。当时，他是他的直系亲属中唯一没有发表过论文的人--他的父母和两个姐姐都是生物医学研究员。教育是非常珍贵的。他被教导说，踩在书上是一种亵渎。当他去波士顿北部的家中看望父母时，他的母亲仍然会给他做一道最喜欢的菜--bhindi（印地语中的 "秋葵"），她告诉我，这应该对大脑有好处。

Chetty的父母都是Chettiar种姓的后裔，这是一个历史上从事银行业的商人群体，孩子们在成长过程中继承了他们的文化传统。除了印地语，他们还学习了泰米尔语。切蒂的姐妹们嫁给了有切蒂尔背景的男人。Chetty拒绝种姓制度，尽管他第一次遇到他的妻子Sundari是在他的一个姐妹通过Chettiar社区认识了她之后。(Sundari是一位干细胞生物学家）。

Chetty一直被公共经济学所吸引--研究政府政策以及如何改进政策。碰巧的是，在他开始职业生涯的时候，该领域的革命正在进行。过去，经济学家不得不严重依赖调查，但廉价、强大的计算机的出现使得一种新的经济学--利用政府收集的大量行政数据。调查的参与者只有几百或几千人；而行政数据可以产生数以亿计的记录。

2007年11月，Chetty看到国税局的一则广告，寻求帮助将其电子文件整理成更容易用于研究的格式。他立即意识到，完成这项工作将使学者们能够更深入地研究税收数据。他和约翰-弗里德曼开始了注册成为联邦承包商的过程--其中包括证明他们的工作场所符合联邦安全标准，并打电话给弗里德曼住在华盛顿特区的兄弟，让他打车去马里兰亲手递交申请材料，一式三份。

像许多好主意一样，这个项目现在看来是显而易见的，但事实是，没有人能够知道这些数据会被证明是多么有用--而且它之所以成功，只是因为切蒂和他的同事有着几乎超人的耐心。

认识Chetty七年的Nathaniel Hendren告诉我，他从未见过Chetty比2014年夏天的一个周五晚上更开心，当时他们坐在波士顿市中心约翰-肯尼迪联邦大楼的一些国税局隔间里。(访问政府数据的唯一途径是在联邦大楼内，在安全的服务器上，由计算机记录他们的请求）。那天晚上，切蒂和亨德伦与数千行代码搏斗，旨在将散落在数以亿计的1040s、W2s和其他表格（为保护隐私，纳税人的名字被分开保存）中的答复拉到一起，同时确保代码中没有任何错误或微妙的偏差。亨德伦回忆说，在某个时候，他听到切蒂大喊 "太好了！" 亨德伦看过去，切蒂微笑着解释说，他当晚离开洛根机场的航班刚刚被推迟：有更多的时间来工作。

在过去的20年里，经济学家们试图尽可能地将他们的工作结构化，以类似于科学实验。这场 "信誉革命 "是试图明确地将原因和效果联系起来，并将相关不等于因果的老批评扫到一边。Chetty和他的同事构建的大型税收数据库的优势之一是，它允许 "准实验"--巧妙的统计方法接近真正的实验的力量，而不需要研究人员，例如，随机分配儿童生活在不同的城市。

例如，Chetty和Hendren研究了改变城市的儿童。他们发现，孩子越晚搬到机会较多的地区，搬迁对未来收入的影响似乎越小。但他们也设计了额外的测试，以确保这种影响是因果关系，例如研究同时搬迁的兄弟姐妹：一个准实验，两个孩子在同一个家庭中长大，但根据他们搬迁时的年龄，在一个新的地区接触的时间较短或较长。其结果是基于数百万个数据点得出的高度可信的结论，即孩子搬到一个更好的社区会提高他或她未来的收入，而且孩子越小，好处越大。

然而，有一个重要的问题：他们的结论与近几十年来最有影响力的贫困实验之一相矛盾。在20世纪90年代，联邦政府推出了 "走向机会 "计划，旨在将居住在公共住房的家庭重新安置到更安全的社区，在那里他们可以获得更好的工作和学校。五个城市的数千个家庭被随机挑选出来，接受住房券和支持服务，帮助他们搬到较低的贫困地区。经过十年的研究，研究人员得出结论，虽然这些 "搬家 "的家庭经历了一些身体和心理健康的好处，但孩子们的考试成绩并没有上升，也没有迹象表明成年人或年长的孩子有经济上的好处。

2014年，切蒂、亨德伦和哈佛大学经济学家劳伦斯-卡茨要求美国国税局和监督该计划的住房和城市发展部允许他们再看看孩子们的情况。当早先的跟踪调查完成后，最年轻的孩子在十几岁之前就搬走了，他们还没有达到挣钱的年龄，而这一点证明了所有的差异。经济学家们发现，这群年轻的搬家者比那些没有搬家的人多赚了31%，其中有4%的人上了大学。他们计算出，对于一个8岁的孩子来说，未来的额外收入在一生中的价值几乎是100,000美元，这对于一个贫困家庭来说是一笔巨款。对于一个有两个孩子的家庭来说，为额外收入支付的税款超过了该计划的成本。"普林斯顿大学的社会学教授凯瑟琳-艾丁告诉我，"最大的启示是，效果要经过一代人的努力才能体现出来。"

去年7月，我和大卫-威廉姆斯（David Williams）一起参观了夏洛特，这位34岁的 "机会洞察"（Opportunity Insights）的政策主管是负责将切蒂的研究转化为实地行动的人。威廉姆斯和他的团队成员挤在一辆白色福特探险家的后面，手里拿着彩色打印的夏洛特各个街区的地图集。卡罗莱纳州基金会的布莱恩-科利尔坐在前座，担任向导。

当司机向东北方向行驶时，"上城 "的高楼大厦突然转变为低矮的建筑和铁丝网围栏。科利尔指出，在快速绅士化的洛克伍德社区有一个男子收容所，他最近在那里看到了一桩毒品交易，就在距离一栋售价50万美元的房子不远处。

我们继续前往Brightwalk，这是一个新的混合收入开发项目，有一排排的联排别墅，然后向西转，在西夏洛特高中周围转了一圈，该校曾是成功融合的典范。但在20世纪90年代，对校车的支持逐渐减弱，1999年，一名法官宣布，种族不能作为学校分配的一个因素。现在，学生人口几乎都是少数民族，而且绝大多数都是穷人，周围的社区在地图上是深红色。这里的房子都是整齐的单层独栋别墅，边缘有点粗糙，但与底特律的烧毁的建筑完全不同，威廉姆斯之前在那里为市长做经济发展工作。"这提醒你，要知道真正的机会在哪里是多么困难，"威廉姆斯说。"你不可能只看到它。"

机会并不等同于富足。考虑一个在年收入约为27,000美元的家庭中长大的孩子，在全国范围内正好是第25个百分点。在贝弗利森林，一个相对富裕的，大部分是白人的飞地，在南夏洛特，有宽敞的，维护良好的院子，他可以期望他的家庭收入在35岁时达到42,900美元。然而，在亨特斯维尔（Huntersville），一个有吸引力的北部郊区，其平均家庭收入几乎与贝弗利森林相同，一个类似的孩子可以预期只有24,800美元--一个明显的差异，对一个过路的司机来说是看不见的。

这种态势在较贫困的地区也有作用。里德公园是夏洛特西侧的一个非裔美国人社区，靠近机场--这个地方一直在努力从20世纪80年代的犯罪流行中恢复过来--对于一个孩子来说，35岁的预期家庭收入平均为17,800美元，令人沮丧。但在夏洛特东南部的白人工人阶级社区东森林，预期的未来收入跃升至32,600美元。

在全国各地的城市都有像东森林这样的地方。切蒂和他的团队将这些地方称为 "机会便宜货"：租金相对可承受的地方，在机会方面比它们更有优势。他还不知道为什么有些地方是机会便宜货，但他认为发现这些社区是一个突破。约翰-弗里德曼告诉我，如果政府能够在最初的 "向机会进军 "实验中把家庭转移到机会便宜的社区，即选择机会较多而不是贫困较少的地方，那么孩子们的收入改善将是两倍以上。

在切蒂地图集的深红色区域，问题既是缺乏机会，也是存在机会的反面：能把人拖下水的急流。
Chetty的团队已经开始在其另一个合作城市西雅图应用这一概念，与当地的两个住房管理局合作，在将研究转化为可衡量的社会变革这一棘手的过程中摸索。贫困家庭很难管理一个广泛的住房搜索，这需要时间、交通和体面的信用。该小组创建了一个有 "住房导航员 "的项目，他们将参与者引向机会相对较多的地区，帮助解决与信贷有关的问题，甚至带他们参观社区。房东们也需要鼓励。他们可能对持有住房券的租户有戒心，这意味着政府的监督和文书工作。西雅图的项目简化了这一过程，并提供免费的损坏保险以增加交易的甜头。

租户们刚刚开始搬家，但该计划已经很成功。大多数接受援助的家庭搬到了机会较多的地区，而对照组只有五分之一，他们没有得到额外的服务。切蒂估计，该计划将使每个孩子的终身收入增加88,000美元。今年2月，唐纳德-特朗普总统签署了一项法案，提供2800万美元，在其他地方尝试类似的实验项目。该法案获得了压倒性的两党支持，今年春天，切蒂被邀请向住房和城市发展部介绍情况。他告诉我，他希望该计划能够扩大到每年接受住房和城市发展部住房券的220万个家庭。"他说："那么你就会真正对美国城市的贫困问题有所作为。"我喜欢这一点的原因是它不是一些空中楼阁。我们有一些有效的东西。"

夏洛特是有兴趣实施西雅图战略的城市之一，但官员们也想利用地图集来为经济适用房选择更好的建筑地点。过去，该市的大部分经济适用房都建在切蒂的数据所显示的高贫困、低机会的地区。"威廉姆斯说："我们不要只考虑建造X个单位的新经济适用房。"让我们真正利用住房政策作为社区更大的经济流动性议程的一部分。"

然而，机会交易并不是一种取之不尽的资源。伯克利经济学家Enrico Moretti说，关键的问题是，这些地方的机会是否来自于 "对手商品"--能力有限的机构，如学校，或 "非对手商品"，如当地文化，这些商品更难被消耗。当新人们搬进来时，机会会发生什么变化？即使家庭的涌入没有破坏机会的魔力，人们也不总是急于拿起和离开他们的家。搬家打破了与家人、朋友、学校、教堂和其他组织的联系。"真正的难题是如何解决不平等的更大的结构性现实，"哈佛大学社会学家罗伯特-桑普森说，"而不仅仅是试图让人们搬家。"

对于他所了解的美国的机会所在，切蒂对是什么让一个地方比另一个地方更好了解得很少，令人惊讶。他和亨德伦收集了一系列社会科学数据集，并寻找与地图集的关联性。他们发现，高机会的地方往往有五个特点：好的学校、更高的社会凝聚力、许多双亲家庭、低水平的收入不平等，以及按阶级或种族划分的住宅隔离很少。这份清单是提示性的，但很难解释。

例如，关联性最强的是完整家庭的数量。解释似乎很明显：第二个父母通常意味着更高的家庭收入，以及更多的稳定性，更广泛的社会网络，额外的情感支持，和许多其他无形的东西。然而，儿童的向上流动与双亲家庭密切相关，只是在邻里之间，而不一定在他们的家里。这个数据可能想说的事情太多了。也许邻里之间的父亲可以作为导师和榜样？也可能根本就没有因果关系。例如，也许有强大的教会社区的地方在帮助孩子的同时也促进了强大的婚姻。每一种关联都会产生同样的问题；每一种关联都可能意味着许多事情。什么是原因，什么是结果，我们错过了什么？Chetty的显微镜揭示了一个新的世界，但不知道是什么让它活跃起来，或者如何改变它。

切蒂发现，机会与许多传统的经济衡量标准，如就业或工资增长并不相关。在寻找机会的原因时，他转而关注从社会学中借用的一个概念：社会资本。这个术语广义上指的是使一个人在这个世界上走得更轻松的一系列关系，提供支持和灵感并打开大门。


Chetty认为，如果可以足够精确地测量向上流动，就可以理解它。"大的目标，"他告诉我，"是要恢复美国梦。" (Carlos Chavarría)
长期以来，经济学一直扮演着社会学中令人讨厌的哥哥的角色--传统的成就和全心全意的自信，不知道自己不知道什么，同时仍然指挥着所有人的注意力。不过，切蒂是年轻一代学者中的一员，他们接受了一种跨越古老学科界限的定量社会科学风格。在他的研究中，有强烈的暗示，社会资本和流动性是密切相关的；即使是对社会资本的粗略衡量，如一个街区的保龄球道数量，似乎也与机会相关。他的数据还表明，你在成长过程中认识的人可以产生持久的影响。他与人合著的一篇关于专利的论文发现，如果年轻女性在童年时搬到了有许多女性发明家居住的地方，她们就更有可能成为发明家。(男性发明家的数量影响不大。)甚至发明家在哪个领域工作也受到他们小时候周围的发明的严重影响。那些在湾区长大的人在计算机和相关领域的专利申请率最高，而那些在明尼阿波利斯（许多医疗设备制造商的所在地）度过童年的人倾向于发明药物和医疗设备。

社会学家接受了许多理解世界的方法。他们跟踪人们，进入社区，想知道他们可能发现什么。他们收集数据，做定量分析，阅读经济学论文，但他们的工作也受到心理学和文化研究的启发。"与切蒂合作的斯坦福大学社会学教授大卫-格拉斯基（David Grusky）说："当你从实验的苛刻要求中释放出来时，你可以做出新的发现，更自由地思考正在发生什么。我问普林斯顿的爱丁，她认为最终会有一件事最能解释美国机会的高峰和低谷。她说，她的最佳猜测是 "某种社会粘合剂"--通过运作良好的机构，无论是清真寺还是社区足球联盟，将人们联系起来。Opportunity Insights的工作人员已经学会了。当一个经济学家迷路时，社会学家可以摸摸他的胳膊肘，说：你知道，我一直在注意一些事情。

在夏洛特，Chetty仍然渴望实行 "精准医疗"，但他告诉我，他最初的目标是比较温和的：看看他和他的团队是否能找到有帮助的东西。Opportunity Insights正在计划住房和高等教育举措，但社会资本是其方法的核心。它正在与一个名为Leading on Opportunity的当地组织合作，并关注那些已经成功运作的非营利组织，包括Communities in Schools，一个提供全面学生支持的全国性组织，以及一个名为Year Up的就业培训项目。Chetty还在使用税收数据来衡量数十种基于地方的干预措施的长期影响，如企业区，它使用税收和其他激励措施来吸引企业进入经济萧条地区。(他预计今年晚些时候将看到这些分析的初步结果。）切蒂可能还没有很多答案，但他相信，这种数据、合作和实地调查的结合将使我们有可能从有根据的猜测转向量身定做的处方。"Chetty告诉我说："当这些碎片聚集在一起时，会有一些点。"我的直觉是，在社会科学领域，这一代人就是这种情况发生的时候。"

切蒂对全国的宣传是，我们的问题有技术专家的解决方案，但有时我感觉他在回避一个论点。当然，我们的社区可以得到改善，而这些改善可以帮助下一代取得更好的结果。但是，推动美国财富巨大差异的更大力量呢？如果穷人的孩子有更好的前景，而且如果他们有更多的钱--如果我们的社会成果得到更广泛的分享，那么他们的生活会更好。"我可以从你那里拿钱给我，也许那是好事，也许不是，"他说。"我觉得有很多人都在研究再分配问题，在那里很难找出正确的答案。" 关注谁得到什么的问题，当然也是政治上的煽动性问题。

切蒂认为，通过一个不那么党派的道德框架，可以取得更多进展。"他说："外面有那么多孩子，他们可以为自己和世界做很多伟大的事情。切蒂对系统的挑战是有分寸的，也是有经验的；这是一个亿万富翁和公司可以欣然赞同的挑战。但他的立场也是一个简单的个性问题。Chetty不是一个煽动者。他告诉我，"我喜欢找到让房间里的每个人都满意的解决方案，这绝对有这种感觉"。

在夏洛特，即使是切蒂正在尝试的限定版本的社会变革也显得很艰巨。去年夏天，在Opportunity Insights团队来到这里之前，我开车绕到西夏洛特高中的后面，来到一个由淡黄色的临时教室建筑组成的小村庄，每栋建筑都镶嵌在混凝土块上。其中一栋楼已经交给了 "消除数字鸿沟"（Eliminate the Digital Divide），即E2D，这是一个非营利组织，接受旧笔记本电脑的捐赠，然后翻新并以每台60美元的价格分发给那些没有自己电脑的学生。据E2D称，该县一半的公立学校学生因为没有电脑或互联网而无法完成家庭作业。

在E2D大楼内有一个明亮的房间，周围是一系列的工作站，西夏洛特的学生员工在这里检查笔记本电脑，安装硬盘，并测试最终产品。墙上挂着白板、照片和海报，上面写着鼓舞人心的短语，如大学毕业！。门边有一对黄色的沙发作为等待区。当男孩们拿到他们的电脑时，他们努力压抑着笑容，而女孩们则很容易放纵。有时他们上蹿下跳，有时他们会哭。

我遇到了卡利贾-琼斯，一个身穿淡粉色无袖上衣和配套裙子的年轻黑人妇女。她在2017年大四时开始在E2D工作。在我们谈话不久，她说："我爱我的生活！"--尽管她当时住在一个无家可归的收容所。

对琼斯来说，E2D带来的最大好处不是电脑或工作，而是该项目提供的社会资本。她说，去年，E2D的西夏洛特实验室被授予当地技术奖，创始人邀请琼斯和她的一些同事一起参加在骑士剧院举行的颁奖仪式，夏洛特芭蕾舞团就在那里演出。其他获奖者之一是Road to Hire项目，该项目在培训高中毕业生从事销售和技术工作的同时为他们提供报酬。雇佣之路 "的负责人出席了仪式，他给了琼斯一张名片，这使得他在该计划的培训项目中获得了一个付费名额。

但在切蒂地图集的深红色区域，问题既是没有机会，也有其反面的存在：能把人拖下水的急流。在这些地方，有几条通往成功的狭窄道路，也有99条失败的途径。琼斯尽管住在收容所，但还是读完了高中，并被西卡罗莱纳大学录取，获得了财政援助。但她决定不去，部分原因是她无法想象把挣扎的母亲和妹妹留在三小时外的校园里生活。去年冬天，他们三个人离开了夏洛特，以及在那里开始为琼斯打开的前景，搬到了她长大的新泽西。当我最后一次与她交谈时，她已经在亚马逊的一个仓库找到了工作。

一个星期五的晚上，我在切蒂的斯坦福办公室里，一个芭蕾舞演员来了。桑维，切蒂3岁的女儿，穿着粉红色的芭蕾舞裙，配着发带和紧身衣。她强烈地拒绝了为她提供的抵御晚间寒意的白色毛衣。切蒂和我花了几个小时讨论他的研究，但当保姆把桑维送走时，这标志着一天的工作已经结束。切蒂收拾好他的东西，把她抱在怀里。"好好抱着我，阿帕，"桑维告诫道。在外面，我们坐上了切蒂那辆陈旧的银色讴歌车，前往一家印尼餐厅吃外卖。桑维热情洋溢。"我想成为一个仙女公主，"她在后座上宣布。"我可以成为一个仙女公主吗？" 切蒂瞥了一眼后视镜，向桑维保证，当她长大后，她可以成为她想要的任何东西。

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在停车买菜后，我们把车停在一栋浅棕色的牧场房子前，门前有美丽的植物。在里面，这所房子显然是桑维的。在开放的厨房里坐下来，我被贴在墙上的大量手指画所包围，其中穿插着从着色书上整齐地撕下的画页（企鹅、鹦鹉、兔子，每一个都是色彩斑斓的）。后面有一对柿子树正在结果。

切蒂告诉我，他对贫穷的兴趣可以追溯到他在新德里街头观察到的可怕的匮乏。但只有当他建立了他的地图集的第一个版本时，他才知道他应该怎么做。"他说："我意识到，"我们可以通过关注儿童对贫困产生最大的影响。

切蒂像经济学家那样思考革命：作为边际变化的复合积累。把你的储蓄账户的利率提高一个档次，30年后，你的余额就会大大增加。把一个家庭搬到一个更好的邮政编码，或在该家庭目前的社区培养合适的条件，他们的孩子就会做得更好；这样做一千次，或一万次，美国梦就会比今天更有可能，对更多人来说。

在20世纪30年代，诗人兰斯顿-休斯（Langston Hughes）发表了对这个梦想最真实的描述之一。

一个如此强大、如此勇敢、如此真实的梦想
即使它强大的胆量也在歌唱
在每一块砖头和石头中，在每一条翻开的沟渠中
使美国成为现在的土地。
不过，这首诗中还夹杂着抗议的内容。"美国对我来说从来不是美国"--不是对 "从未出人头地的人"；"多年来以物易物的最贫穷的工人"；或 "黑人，你们所有人的仆人"。然而，尽管它的愤怒，这首诗以一种自相矛盾的渴望结束。休斯写道："哦，让美国再次成为美国"。"那片从未出现过的土地"。

Chetty在新德里的时候听到了关于美国梦的故事，他接受了这种信仰。当他成为一名科学家时，他识破了真相。剩下的就是矛盾了。我们必须相信梦想，我们必须接受它是虚假的--那么，也许我们将有能力建设一片土地，在那里它还会是真的。

本文出现在2019年8月的印刷版上，标题为 "拉吉-切蒂的美国梦"。

* 这篇文章最初说明尼阿波利斯是梅奥诊所的所在地。

加雷斯-库克是普利策奖获得者，也是《纽约时报》杂志的特约撰稿人。