News this Week

Science  23 May 2014:
Vol. 344, Issue 6186, pp. 784

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  1. Random Sample

    Planet hunter gets a second life

    A world with two suns: artist's concept of Kepler-16b, one of the spacecraft's discoveries.


    A year after it lost its bearings in space, NASA's exoplanet-hunting Kepler spacecraft has received a second lease on life. NASA last week approved $20 million in new funding to keep the Kepler mission going for two more years—with a little help from the sun. Launched in 2009, Kepler has helped astronomers identify scores of planets orbiting nearby stars, including the recent discovery of the first Earth-like planet in a star's habitable zone. Last year, two of the spacecraft's four gyroscopic positioning wheels stopped working; aiming the telescope precisely takes three. Now, however, mission managers have devised a plan to aim the telescope with only two working wheels and an assist from the subtle pressure of solar radiation. Kepler will now limit observations to targets along the ecliptic plane—the plane on which the orbital paths of planets in our solar system lie. Kepler's second run—dubbed the K2 mission—is expected to begin with observations starting 30 May.

    "If general relativity can make a 5-year-old cry, science becomes meaningful."

    Physicist Brian Greene, speaking at this week's The Future Is Here Festival about his son's emotional reaction to the ending of his book Icarus at the Edge of Time.

    Next stop: the twilight zone

    Schrier and Smithsonian zoologist Carole Baldwin in the Curasub.


    Three years ago, Adriaan "Dutch" Schrier turned his hobby into science. A Curaçao businessman who founded an aquarium and was a scuba diver for almost 50 years, he gave up breathing mixed gases when he turned 60. But, still eager to visit the underwater world, he built the "Curasub," a submersible that seats five. In 2011, Schrier invited scientists at the Smithsonian Institution's National Museum of Natural History to take a peek at the ocean's barely lit twilight zone between 200 and 1000 meters, depths relatively unexplored because they are too deep for divers and not challenging enough for deeper diving submersibles. Since then, researchers have extensively surveyed the reef off Curaçao; discovered dozens of new species such as the yellow-spotted golden bass, described last week in PLOS ONE (; and installed temperature loggers and collection platforms for long-term monitoring. Even after 1200 runs, "every trip I go down I find something completely new," Schrier says. And he likes the solitude: "When I'm cruising down at 600 or 700 feet, there's no stoplights, no traffic; you're the only one down there."

    By the Numbers

    80,000 Estimated weight, in kilograms, of a new species of titanosaur unveiled 17 May. The fossils, found in Argentine Patagonia, suggest the dinosaurs may have been the largest to walk the Earth.

    6 Number of years by which global average lifespan increased from 1990 to 2012, according to the World Health Organization.

    60 Percent by which e-cigarettes improve a smoker's chances of quitting compared with nicotine replacement therapies or willpower alone, according to a 21 May study in Addiction based on self-reported data.

    Meeting tweeting, in cartoons

    Stanford University geneticist Michael Snyder discusses personalized genomics.


    For Alex Cagan, 140 characters were just not enough. At the Biology of Genomes meeting earlier this month in Cold Spring Harbor, New York, this graduate student from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, contributed 54 cartoons to the Twittersphere. During each talk, he drew a caricature of the speaker and added a few choice phrases. At meetings, he likes to draw the speaker whenever he takes notes, regardless of whether he's tweeting. "When I try to remember the talk, if I have notes with the actual person, it triggers my memory," he explains. "When I just have text, it's harder to remember." His tweets were well-received, with one fellow tweeter commenting that the sketches "are wonderful and, unlike most conference tweets, actually informative!"

  2. Around the World

    China embraces open access
    Washington, D.C.
    U.S., Cuba ocean science summit
    A new Longitude Prize
    Transparency U-turn?
    Prince William Sound, Alaska
    Gliders sample glacial plumes
    Washington, D.C.
    Congress pushes for faster cures


    China embraces open access

    The Chinese Academy of Sciences (CAS) has adopted a policy of open access for scientific papers resulting from publicly funded research. "Open access will facilitate the dissemination and utilization of knowledge, [and] turn the knowledge produced by public investment effectively into innovation," CAS noted in a 15 May statement. CAS researchers will now be required to deposit copies of articles published in academic journals into new repositories managed by their respective institutes. These databases will make articles publicly available online within 12 months. The move puts CAS in line with policies in the United Kingdom and at the U.S. National Institutes of Health that require free access to taxpayer-funded research papers within 6 to 12 months.

    Washington, D.C.

    U.S., Cuba ocean science summit

    One potential area of U.S.-Cuba cooperation: mangrove ecosystems, home to largemouth black bass.


    Marine scientists from Cuba and the United States are planning a push to improve collaboration between the two estranged nations. At an unusual 13 May meeting hosted by Senator Sheldon Whitehouse (D–RI), researchers and policymakers from both nations discussed existing projects and future possibilities. On the agenda: drafting a new bilateral agreement on marine research and revising trade rules that make it hard for people and scientific equipment to move between the two nations. The idea is to "use marine science as a form of diplomacy," says marine biologist David Guggenheim, president of the nonprofit Ocean Doctor and a meeting organizer. Whitehouse, a vocal supporter of ocean science, has said he'll take the lead on drafting the agreement, which would need White House approval.


    A new Longitude Prize

    John Harrison won the original Longitude Prize in 1714.


    In 1714, clockmaker John Harrison cracked a seemingly intractable problem: how to find the longitude of a ship at sea. With his marine chronometer, Harrison won the £20,000 Longitude Prize, offered by the British Parliament for what it considered the most challenging conundrum of the 18th century. Now, 300 years later, the United Kingdom is looking for the next John Harrison—and has raised the stakes to £10 million. But first, there needs to be a modern-day challenge to solve. People can vote online or via text for one of six themes—flight, food, antibiotics, paralysis, water, and dementia—beginning on 22 May; the chosen challenge will be announced on 25 June, and experts will then convene to fine-tune exactly what criteria must be met to win the prize, sponsored by the charity Nesta and the U.K. government–funded Technology Strategy Board. Anyone around the world is eligible to enter their invention—but it could be years before a winner is chosen, noted Geoff Mulgan, Nesta's chief executive.


    Transparency U-turn?

    Researchers are worried that the European Medicines Agency (EMA) is backpedaling on a pledge to open clinical trials data to public scrutiny. Draft documents dated 5 May say that registered users would only be allowed to view trial information on screen and would not be permitted to "download, save, edit, photograph, print, distribute or transfer the information." "I am now concerned about what appears to be a significant change in EMA's policy, which could undermine the fundamental right of public access to documents established by EU law," said European Ombudsman Emily O'Reilly in a statement on 16 May. EMA spokesman Martin Harvey-Allchurch denies that the agency is reneging on its promises. He stresses that the plans are still open for discussion before EMA presents the revised draft policy to its managing board on 12 June.

    Prince William Sound, Alaska

    Gliders sample glacial plumes

    A wave glider analyzes glacial plumes in Prince William Sound.


    Two sensor-packed remote-controlled wave gliders—bearing a strong resemblance to nerdy yellow surfboards—are part of a new study in the Gulf of Alaska that is helping scientists understand the impact of melting glaciers on ocean acidification. Plumes of fresh glacial water, which peak in summer and fall, have lower alkalinity than seawater, reducing the ocean's ability to buffer against increasing acidification. That can make the waters more corrosive to organisms that build shells. The solar cell–powered gliders will spend 5 months collecting data for the study, funded by the National Oceanic and Atmospheric Administration. A third underwater glider will slide beneath the surface to hunt for freshwater plumes. The robotic fleet, which set sail earlier this month, is scheduled to work through early September.

    Washington, D.C.

    Congress pushes for faster cures

    Members of the U.S. House of Representatives have launched a multiyear effort to modernize the country's system for developing and approving drug treatments. The so-called 21st Century Cures Initiative, spearheaded by Energy and Commerce Committee Chair Fred Upton (R–MI) and Representative Diana DeGette (D–CO), held its first hearing this week to get input from experts involved in a September 2012 President's Council of Advisors on Science and Technology report on drug innovation. In coming months, the initiative will solicit feedback from the Food and Drug Administration, the National Institutes of Health, as well as scientists, industry experts, and patients, before considering possible legislation.

  3. The Science of Inequality

    A world of difference

    1. Emily Underwood

    New data allow researchers to map inequality the world over

    About these data

    The world Gini data, collected between 2008 and 2012, cover 117 countries and were prepared for Science by researchers Branko Milanovic and Janet Gornick of the Luxembourg Income Study Center at the City University of New York's Graduate Center. The Gini index was calculated from household-level data gathered by surveys, except in China and Japan, which do not release microdata to researchers but publish only summary results. The definitions used were disposable household per capita income (after cash social transfers and direct taxes) or household per capita consumption, both calculated across individuals. Gini may be underestimated in countries such as India, which collect data on expenditures rather than income. Databases used are: the Luxembourg Income Study Database, the Socio-Economic Database for Latin America and the Caribbean, the World Bank Europe and Central Asia database, the World Bank's POVCAL, the World Bank's World Income Distribution database, and the "All the Ginis" database.

    U.S. data are based on 2012 U.S. Census Bureau surveys of 122,459 households. They include income received on a regular basis before income taxes, but do not include noncash benefits such as food stamps.


  4. The Science of Inequality

    The ancient roots of the 1%

    1. Heather Pringle

    Don't blame farming. Inequality got its start among resource-rich hunter-gatherers

    In 79 C.E., the year Mount Vesuvius destroyed it, Pompeii was not one city but two. Its wealthiest families owned slaves and lived in multistoried, seaside mansions, one of which was more than half the size of the White House. They dined in rooms with costly frescoes, strolled in private gardens, and soaked in private baths. Meanwhile, at least one-third of all Pompeiian households scraped to make ends meet, with families dwelling in single rooms behind workshops, in dark service quarters, or in small houses. Such economic disparities were common in the Roman Empire, where 1.5% of the empire's households controlled 20% of the income by the late 2nd century C.E., according to one recent study.

    Inequality has deep archaeological roots. Yet if existing traditional societies are any guide, our hunter-gatherer ancestors were mostly egalitarian (see sidebar, p. 824). How and when did a few members of society begin to amass wealth?

    Farming has long been blamed for the rise of inequality. Relying on evidence from the Near East, researchers suggested that the earliest elites emerged after 10,500 years ago, when people successfully domesticated plants and animals and settled in large permanent villages. In this view, agriculture led to the production of surpluses and the emergence of managers, craftspeople, and other specialists, who eventually gained control over extra resources.

    A Pompeiian fresco shows the Roman 1% living the good life.


    Now, analyses of archaeological sites as well as ethnographies of traditional societies are etching a more complex picture, suggesting that some ancient hunter-gatherers may have accumulated wealth and political clout by taking control of concentrated patches of wild foods. In this view, it is the ownership of small, resource-rich areas—and the ease of bestowing them on descendants—that fosters inequality, rather than agriculture itself.

    The transition from egalitarianism to societies rife with economic competition and inequality was “the single most critical watershed in the last 2.5 million years of human history,” says archaeologist Brian Hayden of Simon Fraser University (SFU), Burnaby, in Canada. Over time, it paved the way for the development of “chiefdoms, states, and ultimately industrial empires.”

    BEFORE FARMING. Archaeologists have spotted the earliest glimmers of inequality among the Natufians of the Eastern Mediterranean, one of the first peoples to embark on the long transition to farming. Beginning some 14,500 years ago, the Natufians began settling at least part-time in small villages amid rich food resources, regularly supplementing their diet of wild game, fruits, and nuts with wild cereals—a lifestyle that ultimately led to agriculture.

    Natufians left some traces of inequality behind. Archaeologists T. Douglas Price of the University of Wisconsin, Madison, and Ofer Bar-Yosef of Harvard University examined published reports for 25 Natufian and later sites dating between about 15,000 and 8000 years ago. The two looked for standard archaeological markers of inequality: disparities in grave goods, house sizes, and the ornamentation of the dead. Not surprisingly, inequality markers became more common between 10,500 and 8200 years ago, as early farmers began sowing domesticated einkorn wheat and other plants and tending domesticated sheep and goats.

    But signals of incipient inequality appeared well before that, between 14,500 and 12,800 years ago, while the Early Natufians were still hunting and gathering, Price and Bar-Yosef reported in a 2010 volume. Some Early Natufian skeletons were richly ornamented, but the vast majority were not. The wealthiest 8%, for example, were decorated with pendants or marine shells such as Dentalium, imported or traded from as far as 400 kilometers away. At one site, three male skeletons were buried with Dentalium headdresses, one fringed with shells four deep—an impressive display of riches. Natufians also placed carved artworks in a few graves, built houses of varying sizes, and produced large goblet-shaped stone mortars well-suited for preparing or serving food at feasts. Making these mortars “by pecking for many hours is hardly the business of a fully egalitarian society,” noted Price and Bar-Yosef.

    The findings suggest how people took a first tentative step on the long road to inequality. The Natufians lived in an environment of abundance—wild cereal grains flourished in dense patches in the forest, and game was plentiful. As Price points out, the Natufians apparently “were harvesting wild plants in large quantities and storing cereal grains as well.” He thinks that these stored surpluses of wild cereals may have given some Natufian hunter-gatherers an edge over others. “Those surpluses could allow people to begin manipulating things, giving away food and so establishing some dominance behaviors.”

    HOLDING ON TO WEALTH. Other abundant, storable wild foods can lead to surpluses, too, and private ownership of these natural resources could have boosted inequality, creating a new kind of “transegalitarian” hunter-gatherer society.

    Take an ancient village on Keatley Creek in Canada's Northwest Plateau, which was occupied for part of the year by hunter-gatherers between 2500 and 1100 years ago. The village contains more than 115 house pits, the remains of semisubterranean structures with log and earthen roofs, and appears to have had a peak population of as many as 1500 people. The excavation team, led by SFU's Hayden, found that the houses varied dramatically in size, from the square footage of a microapartment to that of a medium-sized house today.

    To understand these disparities, Hayden and his colleagues examined ethnographic records of historic aboriginal societies in the region, which were divided into nobles, commoners, and slaves. The highest status families owned certain resources and passed them down to their children: fences for driving deer into hunting traps and, especially, fishing rocks that jutted out into the Fraser River, which hosted some of the world's richest salmon runs. Owners built fishing platforms out from these rocks, and so could fish in deep waters where the biggest salmon swam. Lower status families had to fish from public areas along the riverbanks with dip nets, and could reach only smaller fish. Families then wind-dried their catch and stored it.

    Since before the Romans, elites have hoarded wealth in gold.


    To see if this private ownership of resources extended back in time, Hayden's team analyzed fish vertebrae excavated from house pits of various sizes. As much as 75% of the fish bone in the large house pits came from big, 4- to 5-year-old chinook and sockeye salmon, laden with calorie-rich fat. In contrast, 100% of the bone in the two smallest houses came from smaller, 2- to 3-year-old salmon likely caught along the riverbanks.

    The findings suggest that inequality began at Keatley Creek some 2500 years ago when a few ambitious, aggressive people capitalized on the salmon's bounty, Hayden says. Aggrandizers who wanted more food than their neighbors likely built fishing platforms out over key fishing rocks and claimed private ownership. These aggrandizers controlled bigger food surpluses than others, but no one stopped them—as can happen to those who refuse to share in other hunting and gathering societies—because there was plenty of food for all, Hayden says. “It is no coincidence that the greatest inequalities on the Northwest Plateau emerged at the most productive fishing locations, where huge surpluses were produced ethnographically.”

    Hayden and his team also found evidence at Keatley Creek of large roasting pits, one of which was large enough to cook food for 500 people. This and other evidence suggested that aggrandizers at Keatley Creek organized feasts resembling historic potlatches, in which a chief cajoled his clan into producing a cornucopia of food as well as obtaining prestige goods such as Dentalium, which these people also prized: They brought the shells in from as far as 300 kilometers away, to wear and to give away to a rival clan. Such feasts publicly displayed the host's power and wealth, and forced rival chiefs to compete. Potlatch guests were expected to reciprocate with goods of greater value, and families who couldn't come up with gifts had to go into debt to get them.

    In a study published in a 2011 volume called Guess Who's Coming To Dinner: Feasting Rituals in the Prehistoric Societies of Europe and the Near East, Hayden argues that elites in Natufian villages may have pursued similar tactics. Like Price, Hayden argues that long before farming, Natufian elites could have amassed large surpluses of food by “owning” natural concentrations of resources, such as groves of pistachio trees, or by constructing drive lanes for hunting gazelles. Massive roasting pits and hearths at some Natufian sites suggest a feasting tradition, too.

    Some researchers think Hayden overemphasizes the role of aggressive, competitive individuals in the origins of inequality, and underemphasizes the role of population pressures or resource stresses. Archaeologist Anna Marie Prentiss of the University of Montana, Missoula, contends that in another ancient Northwest Plateau village in Canada, it was a shortage of food, rather than an abundance, that sparked inequality. Data from her team's excavations at the Bridge River site suggest that the first elites emerged after salmon runs declined about 1200 years ago and the village population plummeted, she and colleagues reported online in December in the Journal of Anthropological Archaeology. They found that some families responded to scarcity by closing off public access to hunting and fishing resources and holding feasts to attract workers to their depleted households, tactics that allowed them to amass more food than their neighbors. Inequality at Bridge River, Prentiss says, “came about as a byproduct of feeding their families” during lean times.

    Prentiss's findings are raising questions about when Keatley Creek's elites first emerged. So Suzanne Villeneuve, project director of the Keatley Creek Archaeological Research Project at SFU, and her team are now excavating and analyzing new housepit data to re-evaluate the site's dating. But Hayden insists that in historical hunter-gatherer cultures both in Canada and abroad, aggrandizers build surpluses, amass wealth items, and hold feasts only when food is abundant. “When food is in short supply, no one tolerates other people hoarding,” Hayden says. “The majority simply take what they need because their lives depend on it. Scarcity breeds revolts and demands for more equality.” In contrast, when times are good—for example in a booming modern economy like China (see p. 832)—people seem more tolerant of inequality.

    HOW THE RICH GET RICHER. While archaeologists on Canada's Northwest Plateau probe the origins of wealth, other researchers are examining how it is passed on from generation to generation, perpetuating inequality. Economist Samuel Bowles of the Santa Fe Institute and anthropologist Monique Borgerhoff Mulder of the University of California, Davis, led an international team that studied inheritance in four types of societies: hunter-gatherers, pastoralists, horticulturalists who planted hand-tended gardens, and agriculturalists who used more advanced technology such as plows or organic fertilizers to boost crop yields.

    Using historical and ethnographic data on 21 populations around the world, the team examined three kinds of wealth: material riches such as real estate, embodied wealth such as physical strength, and relational riches such as the number of people in a person's social network. They conducted statistical analyses to determine how much of each type of wealth was transmitted. “We counted things like the number of cattle people had and their sons had, and we did the same thing for forms of wealth used by hunters, such as grip strength, which measures how strong your forearms are,” Bowles says.

    At Keatley Creek in Canada, elites arose by controlling rich patches of resources.


    They found that only material forms of wealth, such as land and livestock valued by farmers, were readily handed down to children. “I can pass on my cows to my sons, but if I have some phenotypic trait that accounts for my income, like being physically strong, it is less likely that I will pass that on to my offspring,” says Bowles, whose team reported their findings in a paper in Science in 2009 and a series of papers in Current Anthropology in 2010.

    The team found an unexpected difference between horticulturalists and agriculturalists. Horticulturalists, who tended widely scattered fields of domesticated plants, scored little higher than hunter-gatherers in the overall transmission of all forms of wealth. That suggests that just having domesticated crops wasn't enough to fuel enduring inequality. Farmers who practiced intensive agriculture and boosted yields in regions where arable land was scarce readily passed down their wealth. These farmers could control access to their fields, protect them, and leave them to their heirs, Bowles says.

    He thinks resource concentration is a key factor in explaining inequality among both farmers and the ancient salmon fishers. “Those societies had in a natural state exactly the same kind of concentration of resources that farming made possible everywhere,” Bowles says. “Farming vastly increased the productivity of small patches of land and a small number of animals.” People who owned particularly fertile patches of farmland had a good shot at becoming wealthy and passing on that wealth, in part because the land was defendable against others.

    As agricultural societies developed, so did more elaborate hierarchies, evolving into hereditary chiefdoms and eventually kingdoms. In these complex societies, chiefs and kings came up with new strategies for amassing surpluses and concentrating wealth and power. Many chiefs created economic bottlenecks in trade routes, noted economic anthropologist Timothy Earle of Northwestern University in Evanston, Illinois, in a 2011 paper in Social Evolution & History. These leaders then collected payments from merchants for safe passage and used the surplus to finance specialized warriors to defend and extend their rule. Material culture also became ever more sophisticated, multiplying into innumerable kinds of highly concentrated and easily transmitted forms of wealth, from copper ingots to gold jewelry. All of these trends led to ever greater levels of inequality.

    By the time of the Romans, a yawning gap separated rich from poor. Historian Walter Scheidel of Stanford University in California and biblical studies scholar Steven Friesen of the University of Texas, Austin, used historical records to calculate the Gini coefficient—a standard measure of inequality in modern societies—for the Roman Empire. The coefficient ranges from 0, in which everyone shares equally, to 1, in which one wealthy person has everything and the rest have nothing. The Roman Empire's Gini for income was about 0.43, the pair reported in 2009 in The Journal of Roman Studies—close to the 0.49 for pretax income in the United States in 2010. In fact, Rome's super-rich had wealth on the scale of today's billionaires. The income of the wealthy Roman triumvir Marcus Crassus equaled about $1 billion per year today, reported economist Branko Milanovic, of the Luxembourg Income Study Center of the City University of New York in New York City, and his colleagues in a working paper in 2007; that's not quite up to Bill Gates's more than $2 billion per year.

    In today's complex world, there's no going back to the egalitarianism of some hunter-gatherers. And yet studies of prehistory may offer some hope for lessening the grip of the 1%, Bowles says. As societies move toward knowledge-based economies, wealth increasingly reflects know-how, social skills, and networking—factors that cannot be transmitted across generations as easily as plots of land or stock portfolios, he says. “So I think the long-term possibilities for a more egalitarian future are certainly there.”

  5. The Science of Inequality

    Our egalitarian Eden

    1. Elizabeth Pennisi

    Hunter-gatherers—and presumably all our ancestors—lived as equals

    Seek the richest family in a traditional camp of the Ju/'hoansi/!Kung people of the Kalahari Desert in Africa, and you will almost surely fail. There is no such thing. These hunter-gatherers traditionally moved periodically and had few possessions. What they had, they shared—food, weapons, property, even territory. The poorest looking hut in a camp likely belonged to the leader, explains anthropologist Richard Lee, a professor emeritus at the University of Toronto in Canada, because leaders try to avoid looking superior.

    Many anthropologists think this egalitarian lifestyle was an essential feature of hunting and gathering societies. In contrast with both today's titans of Wall Street and the alpha males of the great apes, people in these societies “had an ethic of sharing that was central to their way of life,” Lee says. “No one takes precedence over anyone else.”

    Our species has lived as hunter-gatherers for more than 90% of our history, Lee notes. Today's economic inequality goes back thousands of years (see main story, p. 822) but in evolutionary time it is relatively recent. Although some of our great ape cousins and arguably our ape ancestors lived in sometimes brutal hierarchies, humans adopted an egalitarian way of life for all but the last 10,000 years.

    Achieving and sustaining such egalitarianism is not easy, anthropologists say. “The only way you can avoid hierarchies is that you work very hard to head [them] off,” says Christopher Boehm, a cultural anthropologist at the University of Southern California in Los Angeles. Like all animals, humans are born unequal—some run faster, plan better, or make friends more easily than others. And we instinctively want the best for ourselves, even at the expense of others. That sets the stage for some to dominate.

    Sharing meat helps reinforce equality among the !Kung.


    To find out why humans shunned hierarchies for most of our history, anthropologists have studied living hunter-gatherers around the world, including Native Americans and the Ju/'hoansi/!Kung. Iconic studies of these societies show that boasting and other self-aggrandizing behaviors are not allowed. Offenders are teased, ignored, banned from camp, or, in extreme cases, killed. Humility, humor, and strict protocols about distributing meat helped keep people on an even footing, says Boehm, who has surveyed the ethnographic literature. For example, !Kung people traditionally downplay their accomplishments: A hunter will say he's caught only a small skinny animal, even if it's big and meaty, and his comrades will agree. “You have to demean yourself,” Boehm says.

    Lee and his colleagues, who observed the Ju/'hoansi/!Kung for years, found that to counter differences in hunting prowess, men exchange arrows before they hunt. The owner of the arrow, not the bowman himself, gets the credit and decides how to distribute the meat while everyone looks on.

    Other traditional societies have similar customs, Boehm found in an unpublished analysis. Of today's 330 foraging societies, he examined 56 that live in conditions resembling those of Paleolithic hunter-gatherers. Among these groups, having someone other than the successful hunter distribute the meat “is universal,” he says.

    Several factors prevented the concentration of wealth and reinforced cooperation in these groups. Scattered, unpredictable food resources encouraged nomadism, a lifestyle that ensured no one accumulated many material goods. Cooperative hunting, in turn, yields more than enough meat to go around, and groups that shared equitably were at an evolutionary advantage because all of their members were strong enough to be good hunters or fighters should the need arise, says economist Samuel Bowles of the Santa Fe Institute. And cooperation is self-reinforcing: Sharing the spoils promotes further cooperation and self-sacrifice (Science, 4 September 2009, p. 1196). “Inequality may be the enemy of cooperation,” Bowles says.

    Boehm also stresses that the behavior of the lower ranks can help quell dominant individuals. In a seminal paper back in 1993, he proposed that several low-ranking men could band together to oust a too-greedy or violent alpha male. He confirmed this idea based on a survey of behaviors of 48 seemingly egalitarian groups. This isn't a lack of dominance but a reversal of it, he says: “An apparent absence of hierarchy was the result of followers' dominating their leaders rather than vice versa,” he wrote.

    Over the millennia, as societies began accumulating surplus food and goods, the inequality held in check for thousands of years re-emerged. Yet humans “have experienced an extraordinary amount of equality,” Bowles says. “The question is whether conditions now will allow us to experience the egalitarianism of the past.”

  6. The Science of Inequality

    Tax man's gloomy message: the rich will get richer

    1. Eliot Marshall

    With a massive database of income tax records, a French superstar challenges conventional wisdom on inequality

    On a rain-soaked 15 April—U.S. income tax day—Thomas Piketty arrived early at a think tank in Washington, D.C., with a stack of boxes containing his new book, Capital in the Twenty-First Century. The 43-year-old French economist had come to talk about his radical ideas. The room was packed with young policy wonks and grizzled journalists, lawyers, political aides, and even a former U.S. representative, David Obey, who once chaired a key spending committee in the House of Representatives. Piketty, who sometimes apologizes to audiences for his strong accent, presented his data and predictions for capitalist economies and gently brushed aside criticisms. Dressed in a rumpled jacket and open collar, he looked a bit like a busy graduate student rather than a world-famous economics guru. By the time he was done, his supply of books had sold out. Young and old were lining up for an autograph.

    Scenes like this played out many times this spring as Piketty toured North America. now ranks his book its number-one best-seller, and the publisher, Harvard University Press, reports that the first-year sales of Capital are more than for any title in its 101-year history.

    Despite Piketty's popularity, his message is harsh. He labels as “a fairy tale” the long-accepted idea that wealth and income will be more evenly distributed within nations as they develop, and suggests that even the best run capitalist economies concentrate riches at the top. The reason: In the long run, he says, the return paid to owners of capital is higher than the rate of economic growth.

    These provocative conclusions are based primarily on a huge database of tax records that Piketty and a team of 30 researchers around the globe have assembled from more than 20 countries, including the United States. From atop this mountain of data, Piketty is able to offer a 2-century retrospective view of capitalism and make predictions about its future. The database is, Piketty writes, “the largest historical database concerning the evolution of income inequality.”

    Thomas Piketty foresees a continued rise in inequality.


    It is also the cornerstone of his credibility. Even economists who disagree with Piketty's message acknowledge the importance of his data. The chair of Harvard University's economics department, N. Gregory Mankiw, called it “[t]he best data we have on the upper tail of the income distribution” in a 2013 essay called Defending the One Percent that runs counter to Piketty's views.

    Piketty began this project in the late 1990s, when he dug into old tax records for a book on the distribution of wealth in France. He had received his Ph.D. in 1993 at age 22 from the School for Advanced Studies in Social Sciences (EHESS), then moved to the Massachusetts Institute of Technology (MIT) as an assistant professor of economics. But he quit 3 years later—“I did not find the work of U.S. economists entirely convincing,” he writes in Capital. Back home in Paris, he is now an economics professor at EHESS and the Paris School of Economics.

    Piketty unearthed French data on wealth going back to the 1789 French Revolution, as well as a century's worth of income tax data that hadn't been analyzed systematically. Many such records have been ignored, he writes: “The historical and statistical study of tax records falls into a sort of academic noman's-land, too historical for economists and too economic for historians.”

    Extending the tax data analysis to Britain and the United States, Piketty teamed up with economists Anthony Atkinson of the University of Oxford and Emmanuel Saez of the University of California, Berkeley. Saez and colleagues gained rare direct access to U.S. tax records, enabling them to include new data from the world's top economy in the expanding database (see p. 836).

    The team sifted through 100 years of tax records and stored standardized data in a resource they call the World Top Incomes Database ( In addition to the more than 20 nations now represented, the website claims that about 45 more are “under study” and will be added when the work is complete.

    In his book, Piketty combines income, inheritance, and national wealth data to reach a striking conclusion. Capitalism concentrates riches at the top of society, Piketty argues, because the rate of return to capital (labeled r) is higher than the overall rate of economic growth (labeled g) over the long run. This simple formula (r > g) means that families who own capital tend to acquire more and more wealth.

    This pattern broke down, Piketty concedes, in the mid-20th century. Two world wars and the Great Depression destroyed a huge swath of Western wealth. Following World War II, as nations began to rebuild, they distributed the new wealth more equitably, Piketty finds. Aid programs and progressive tax schemes also decreased inequality, while a concurrent rise in industrial productivity and a population boom boosted economies and benefited the middle class. This golden era lasted roughly from 1950 to 1980, triggering a pause in the concentration of wealth.

    Piketty insists the pause was an aberration. Capital resumed its dominant place in the 1980s, and wealth is again being concentrated at the top of society, he demonstrates. Today, Piketty says, inequality in the developed economies and particularly in the United States has reached an “extreme” point that could lead to “terrifying” disparities in the future and threaten democracy.

    The concentration of wealth will continue, Piketty says, because economic growth is likely to be no more than 2% a year, limited in part by a widely predicted decline in birth rates. He predicts that the rate of return for capital will remain about what it has been historically, 4% to 5%. “It would be an incredible coincidence if the number of children we have and the number of innovations we make push the growth rate up” enough to counterbalance the return on capital, he says. “There's no logical or historical reason why this should happen,” he adds in an e-mail.

    These ideas are important, said economist Robert Solow, a 1987 Nobel Prize awardee and professor emeritus at MIT, who spoke after the first of Piketty's several tax day talks and, in a book review, called his work a “new and powerful contribution” to economics. Economist Branko Milanovic, a former World Bank researcher on inequality now at the Luxembourg Income Study Center of the City University of New York in New York City, says Piketty has pulled several strands of research together into a single framework that offers “a new way of looking at the functioning of a capitalist economy.”

    In France, Piketty (far left) endorsed left-wing political candidates like Ségolène Royal because other choices were worse, he says.


    Critics are sharpening their knives, however. Economist Kevin Hassett of the conservative American Enterprise Institute in Washington, D.C., for example, questions Piketty's reliance on income tax data. Hassett argued at one of the tax day talks that Piketty's approach fails to count the billions of dollars in government “transfers” that flow to citizens for benefits such as medical care and income support. Hassett prefers to rely on U.S. economic consumption data from household surveys run by the U.S. Bureau of Labor Statistics, which he says reveal spending in lower income households that may not even file tax returns. Those surveys don't show an alarming disparity between wealthy and nonwealthy Americans, Hassett says.

    Piketty maintains that tax records give a truer picture of wealth and income at the top. On surveys, people tend to understate their income, while taxpayers are likely to be more truthful because they can be punished if they lie, he says. As for transfer payments, Piketty suggested that these funds increasingly pay for health care in the United States. With a smile, he said it would be interesting to know whether such transfers do more to benefit individuals or health care providers.

    But Piketty's remedy for inequality—a universal tax on wealth that takes little from the bottom of the scale and a lot from the top—has drawn fire from left and right, in part because it would be so difficult to impose. Legislators don't seem ready to try it, doubters point out, and if they did, the super-rich could threaten to move to more tax-friendly climes. At Piketty's first stop, several economists suggested what they consider better and more achievable ways to counter inequality, such as investing in public education, job creation, and infrastructure. At another seminar, economist Dean Baker, co-director of the Center for Economic and Policy Research in Washington, D.C., suggested other remedies. He would tax financial transactions, limit patents to reduce drug company profits, break up monopolies, and more.

    Piketty agreed with those suggestions but said they are not enough to change the fundamental dynamic of r > g. But as the first seminar on tax day came to a close, Solow and others mused on the implausibility of Piketty's scheme—requiring all the world's nations to agree in concert to boost taxes on their wealthiest citizens. Sounding a “pessimistic note,” Solow reminded Piketty and the audience that the United States “is a country that can't even sustain an inheritance tax.”

    Piketty anticipated the pessimism. “In 1900,” he said, “most people would have said a progressive income tax would never happen.” But it happened.

  7. The Science of Inequality

    Physicists say it's simple

    1. Adrian Cho

    If the poor will always be with us, an analogy to the second law of thermodynamics may explain why

    The basic inequality that plagues economies the world over may have a simple explanation—at least, according to physicists who've turned to economics. Pick a country, they claim, and you'll find multitudes of people who earn next to nothing, a few who rake in plenty, and a distribution between the extremes that falls exponentially as income increases (see figure). That distribution applies to all but the very rich, they say, and it arises from an analogy to the concept of entropy, a measure of disorder in a physical system such as a gas. Just as a gas evolves to a state of maximum entropy, they argue, random churning in the economy ensures that the income distribution naturally tends to this inequitable form.

    The argument suggests that although social and economic policy can help individuals edge ahead or perhaps boost everybody's fortunes, nothing short of radical intervention can overcome the forces of randomness and transform the lopsided distribution. An equal sharing of income, in this view, is as likely as the air in your office collapsing into your empty coffee cup. The reasoning is “not very close to the thinking of economists, but it's pretty persuasive,” says Thomas Lux, an economist at the University of Kiel in Germany. But Frank Cowell of the London School of Economics and Political Science says “I'm extremely skeptical” that the argument provides any insight into the economy.

    Natural inequality.

    Econophysicists say the income distribution is, inevitably, a decreasing exponential with few winners and lots of losers.

    The argument builds on the century-old kinetic theory of gases, in which physicists asked: What is the most probable distribution of the energies of the molecules in a gas? That might seem impossible to determine without tracking exactly how the molecules ping off one another. But the puzzle can be solved by simply counting the ways the gas's overall energy can be divvied among the molecules—a number that defines the gas's entropy. The most likely energy distribution is the one that can be achieved by the most combinations of individual molecular energies. That turns out to be essentially an exponential distribution, with lots of molecules of low energy and a few with high energy.

    Victor Yakovenko, a theoretical physicist at the University of Maryland, College Park, applies the same reasoning to income. Suppose you randomly divide $500 million in income among 10,000 people. There's only one way to give everyone an equal, $50,000 share. So if you're doling out earnings randomly, equality is extremely unlikely. But there are countless ways to give a few people a lot of cash and many people a little or nothing. In fact, given all the ways you could divvy out income, most of them produce an exponential distribution of income. So that's what you end up with, even if you start with a different pattern and let random economic activity take over, Yakovenko and a colleague argued in 2000 in The European Physical Journal B. “The exponential distribution is what you would call natural inequality—what you would get from entropy,” Yakovenko says.

    In 2001, Yakovenko and a colleague argued using tax data that income in the United States and both income and wealth in the United Kingdom follow exponential curves, as they reported in Physica A. Such curves also fit income data from Japan, Sweden, and the European Union, others have shown. “I don't know any other place in economics where the theory is so close to reality,” says Mauro Gallegati, an economist at the Polytechnic University of Marche in Ancona, Italy.

    Some economists are unimpressed. Economists gave up explaining the exact shape of the income distribution decades ago, Cowell says. Now, he says, economists estimate inequality using only raw data, and don't depend on knowing the distribution's precise mathematical form.

    An exponential distribution also predicts fewer super-rich people than are found in most economies, and the entropy argument does not explain the balance of wealth between the handful of super-rich and the masses, says James Foster, an economist at George Washington University in Washington, D.C. The idea also fails to account for well-established correlations between income and education, race, and other factors, Foster says, and so is unhelpful in making policy.

    Such criticism misses the point, Lux says. An individual's income can be highly correlated with other factors, he says, even as the distribution of income in a population as a whole appears random—just as the trajectory of a molecule in a gas is in principle predictable even as the motion of all the molecules as a group appears random. “That this is not a contradiction is something that we have to communicate to [traditional] economists,” Lux says.

    Even the theory's supporters say it must be fleshed out. It assumes that, at least over short times, the total amount of income is fixed, notes Duncan Foley, an economist at the New School for Social Research in New York City. If that's true, economists need to explain how that constraint arises. Still, Foley says he finds the physicists' perspective compelling, if bleak. In trying to achieve a more equal income distribution, “you're kind of fighting against the second law of thermodynamics,” he says, “which as we know is generally a losing battle.”

  8. The Science of Inequality

    Can disparities be deadly?

    1. Emily Underwood

    Controversial research explores whether living in an unequal society can make people sick

    Whitehall street, just south of Trafalgar Square in central London, is the heartbeat of the British government. Generations of workers in the highly stratified British Civil Service have marched to work each day in the government offices lining the road, with top bureaucrats working and living in palatial brick mansions built for aristocrats. Over the years, the denizens of Whitehall have fallen prey to the ills of the modern world: Their arteries have filled with fatty plaque; their blood sugar has spiked from diabetes; their lungs have been damaged by emphysema. And with surprising and troubling frequency, lower ranked workers have died earlier from these ailments than have their superiors.

    To find out why, thousands of these civil servants, from typists to top officials, have gone to nearby medical clinics to have blood drawn, fill out questionnaires about how much they exercise and smoke, and don scratchy paper gowns for physical exams. Last year marked the 11th wave of data from this ambitious study, which has run for roughly 40 years and sparked an entire research program on the contentious question of whether being low-ranked can make you sick.

    All agree that compared with the wealthy, poor people are less healthy. A child born in Norway can expect to live roughly 30 years longer than one born in Afghanistan. In the United States, on average, people in the highest income group can expect to outlive those in the lowest income group by more than 6 years. Preventable illnesses caused by poor nutrition and lack of education and care account for much of the disparity. Investing in health care and making it widely available can boost the health of those at the bottom. Redistributing wealth to the lower end of the curve helps, too. One simulation by researchers at the University of Otago, Wellington, for example, showed that shifting New Zealanders' incomes toward the mean income by 10% would save about 1100 lives per year.

    Uninsured people wait for basic health care at a free clinic in Los Angeles.


    But epidemiologist Michael Marmot of University College London (UCL), who leads the Whitehall study, argues that there's more to health than money alone. On the basis of his own and other studies, Marmot argues that hierarchy itself is a threat to health, with low-ranking individuals getting sicker and dying younger than higher-ups in part because of the sheer stress of being low on the social ladder.

    Some public health experts say their own studies bear out Marmot's claim, but others think that confounding factors could easily account for the Whitehall findings. To these skeptics, focusing on hierarchy distracts from the real challenge of providing better health care to the poor. One question is how being low on the social ladder matters to your health. Another is whether a society's health is worse when the rungs are far apart. The issue bubbles just below the surface in policy debates and has erupted recently in impassioned editorials. Some argue, paraphrasing Roman philosopher Seneca the Younger, that “to be poor in a wealthy society is the worst kind of poverty.” But will it send you to an early grave?

    Healthy at the top.

    In the long-running Whitehall studies, civil servants at every occupational grade live longer than their inferiors.

    WHO DIES FIRST? The Whitehall studies began as a simple search for heart disease risk factors. In the late 1960s, heart disease was thought to prey disproportionately upon upper-class, white-collar workers, because of their high-stakes jobs and type A personalities. After following more than 17,000 40- to 64-year-old male Whitehall employees for a decade, however, researchers at UCL found the opposite. During that period, 1652 men died, and men of the lowest rank were nearly four times more likely to die prematurely of heart disease than those in the highest tier, even though all had free health care.

    In 1985, Marmot and his colleagues set out to determine why this might be so. They recruited a second cohort of more than 10,000 white-collar civil servants, including women, and found the same patterns of illness and mortality by rank, with some variations between men and women. Marmot started asking participants to fill out ever more extensive questionnaires, including not only their past medical history and health behaviors, but also their job demands, levels of stress, and social networks and support. As the data rolled in, he found that the psychological effects associated with status and job rank consistently predicted employees' health better than did their salaries, or even health-related behaviors like diet and exercise.


    To hear a podcast with author Emily Underwood, see

    Based on these findings, Marmot developed a theory: When a population moves beyond abject poverty, rank in the social hierarchy, not income, ultimately determines how healthy people are. Some animal studies suggest how status stress might “get under the skin,” as epidemiologists put it: Low-ranking baboons and macaques can develop higher levels of stress hormones, atherosclerosis, and hypertension when subject to a dominant male's whims.

    If Marmot and others are correct, simply shifting money to the poor won't be enough to boost their health. The health gradient among people who are not poor shows that it's “not only about poverty—we've got to improve society,” he says.

    From the dangerous streets of Chicago's South Side to the neatly tended homes of a Helsinki suburb, the link between low status and poor health has now been found in many different countries and contexts, says Ichiro Kawachi, a social epidemiologist at Harvard University. “The higher up the gradient you are, the longer you tend to live and the healthier you tend to be,” he says.

    SCALING UP. More controversial is whether overall population health is worse in more unequal societies. In 2009, Kawachi published a meta-analysis of epidemiological studies linking inequality and health in about 60 million people around the world. He and his colleague found an excess mortality risk of 8% for every 0.05 unit increase in a country's Gini coefficient, the most commonly used statistical measure of the gap between rich and the poor (see p. 818). Although such an effect may seem modest, when extrapolated to the global population it suggests that leveling income inequality could help avert more than 1.5 million deaths per year worldwide—assuming the effect is causal, he says.

    In the United States, Kawachi and public health researcher S. V. Subramanian, also at Harvard, have found that income inequality is also strongly correlated with rates of infant mortality, heart disease, and several health conditions across many states and cities, even after controlling for variables such as absolute income in each location, race, age, and education. Measures of social cohesion such as trust also appear to track with inequality, he says. In one of America's most unequal states, Louisiana, for example, people are far more likely to agree with the statement that “most people would try to take advantage of you if they got the chance.”

    Based on such studies, Kawachi and others argue that inequality breaks down social values, such as trust and support, that protect against both physical and mental illness. In a recent op-ed in The New York Times, epidemiologists Richard Wilkinson and Kate Pickett of the University of York in the United Kingdom took the argument even further. They claim that the reason more unequal countries like the United States see higher rates of schizophrenia and other mental illnesses is because inequality causes “social corrosion” that damages the individual psyche.

    Others aren't convinced. John Lynch, an epidemiologist at the University of Adelaide in Australia, says that although he started out as a “true believer” in the income inequality hypothesis, a string of negative and equivocal studies turned him into a skeptic. Back in a 2004 paper, for example, Lynch and colleagues reviewed 98 cross-national studies and found “little evidence” of a consistent link between income inequality and health, although the United States displayed a more robust association than others. Working on wellestablished public health goals such as reducing smoking and improving the living conditions of the poor will likely have more direct health impacts than targeting relative income gaps, he says.

    The gap between what people desire—like these luxury cars in South Africa—and what they can afford may be a source To hear a podcast of unhealthy stress.


    Even if the correlations Kawachi and others have found hold up, there's no strong evidence that income inequality, per se, is directly damaging people's health, says Angus Deaton, an economist at Princeton University. In American cities and states where there are large proportions of African-Americans, for example, racism, poor health care, and political disenfranchisement could just as easily explain poor health outcomes as income inequality, he says. Deaton argues that extreme inequality is a risk to health chiefly because it skews politics to favor the rich and powerful in society. “I get angry” over Wilkinson's claim that psychological stress is the primary culprit, because it completely deflects from the real issues,” he says.

    CAUSE OR CORRELATE? In 2011, Princeton University economists Christina Paxson and Anne Case found another potential explanation for the correlations between rank and health. They reexamined data from the Whitehall II study and found that adults who were healthier as children started at higher grades in the Civil Service, were promoted to higher positions, and maintained better health throughout their lives. Occupational rank was a marker, but not a cause, of poor health in adulthood, Paxson and Case concluded.

    Many economists agree that people's health influences their status, rather than the other way around, says Dalton Conley, a sociologist at New York University in New York City. “Economists tend to think that your health predicts where you are on the social scale,” he says. If you're sick a lot and miss school, for example, you won't do as well in the labor market. He notes that the initial Whitehall studies also didn't take into account “very controversial” questions about the extent to which genes determine later health and wealth.

    Marmot says he's now persuaded that genetics and early-life experiences do play some role in adult health and socio-economic rank. Still, neither can fully account for the huge difference in mortality and morbidity among Whitehall's occupational grades, he says. Pointing to more than 100 studies based on Whitehall data, Marmot maintains that stressors such as lack of control and harassment at work fall hardest on low-ranking workers and take a fatal toll.

    Causality lies at the heart of the issue, so scientists are now looking for mechanisms that could link inequality and health. Biocultural anthropologist Elizabeth Sweet of the University of Massachusetts, Boston, notes that any causal link assumes that people know their place in the hierarchy. “We don't always walk around with our salaries tacked on our foreheads, so how do we get the information to make that social comparison?”

    Kawachi suggests that for Americans, their own aspirations may provide the point of comparison. Even though an American born in the bottom fifth of the income distribution has only about an 8% chance of rising to the top fifth—half the likelihood of a child born in Denmark—more than 90% of Americans still believe in the American dream, he says, and the collision of their ideal with reality may take a toll on health. “When you work hard on the assumption that we're building a meritocracy, then fail,” the resulting depression and frustration may contribute to the country's high rates of drug abuse, suicide, and violence, he says.

    Similarly, Sweet hypothesizes that the gap between the standard of consumption one identifies with success and one's ability to meet that ideal produces measurable stress and health impacts. Through extensive interviews, she and others collect information about the cultural norms of material success in a given community. In rural Brazil, being successful might mean owning a TV, whereas in U.S. suburbs it might mean having the “right” brand of jeans or cellphone. The researchers measure the degree to which an individual is able to “keep up with the Joneses,” and compare that with health indicators such as the amount of cortisol in saliva, a marker of stress.

    In a study of African-American teenagers in Chicago, Sweet demonstrated that teens who could easily conform to their communities' “ideal” level of consumption had lower blood pressure than teens who couldn't meet those norms. But if they managed to get expensive sneakers and brand-name clothes even though they couldn't really afford them, the students had abnormally high blood pressure. In Sweet's view, this suggests that the tension caused by the gap between what people need and what they can afford can affect health. But she and Kawachi admit that the causal link is tenuous.

    Back at Whitehall, civil servants are still striding into work every morning. Some of the original participants have retired and moved to the suburbs. Many others have died, leaving behind reams of data about what they ate, if they exercised, and how often they felt lonely. Marmot and others have produced more than 500 papers based on these workers' experiences and continue to churn out dozens each year. To fully explain the links between inequality, rank, and health, however, may take hundreds more.

  9. The Science of Inequality

    While emerging economies boom, equality goes bust

    1. Mara Hvistendahl

    Inequality spikes in developing nations around the world

    SHANGHAI, CHINA—Starting in 1949, the Communist government led by Mao Zedong waged war on inequality of all kinds. The administration seized property from privileged classes, imprisoned intellectuals, and appointed teams of workers to run universities. The revolution upended the class structure, and the party campaigned against inherited wealth and gender discrimination. By the time the Cultural Revolution ended and Mao died in 1976, the government had mandated a bland unisex style of dress and effectively abolished property ownership. Society had ostensibly been “leveled off,” even if in practice the new system concentrated resources in the hands of party cadres.

    Then, beginning in the 1980s, the country pulled an abrupt about-face. China reintroduced land rights, allowed foreign investment, and spurred private enterprise in a few designated areas. Inequality was no longer the enemy; in fact, the government signaled that it was to become the new norm. The reformist leader Deng Xiaoping disparaged Mao's egalitarianism as “everyone eating from the same big pot.” Overturning that failed ideal would bring growth to everyone eventually, he suggested: “It is good for some people to get rich first.”

    Some people did. China now has more than a million millionaires and more than 200 billionaires. Although no country can quite match this meteoric rise, similar stories have played out across the developing world. For example, the Latin American middle class mushroomed from roughly 100 million in 2000 to about 150 million a decade later, according to the World Bank.

    But a rash of new studies—based on longitudinal surveys, better cross-sectional data, and renewed attention from scholars—has also laid bare extraordinarily high levels of inequality in these growing economies. In China, the richest 10% now makes 13 times as much as the poorest 10%, compared with five times as much in the United States, according to data from the China Family Panel Studies, run by Peking University's Institute of Social Science Survey in Beijing. With economic development, “the rising tide has indeed raised all boats,” notes University of Maryland, College Park, sociologist Reeve Vanneman. “But the big yachts have done better, so overall income inequality is increasing.”

    That's not what many 20th century economists would have predicted. In a 1954 speech at an American Economic Association meeting, economist Simon Kuznets proposed that the urbanization that accompanies development inevitably triggers a growing income gap, but that societies become more equal as they democratize and adopt social welfare programs. When inequality was plotted against income levels, Kuznets maintained, the relationship looked like an inverted U curve—first rising, then falling. He won a Nobel Prize for his work.

    Laborers work on new construction in the booming city of Chongqing, China.


    But his analyses were based on data from the United States, the United Kingdom, and Germany in the 20th century. Kuznets himself cautioned that the hypothesis needed further testing. “The Kuznets curve is a perfect example of taking trends observed in wealthy countries and projecting [them] as universal to the world,” says Timothy Moran, a sociologist at Stony Brook University in New York.

    In fact, the curve's predictions have not held up in many countries. Initial growth between the 1960s and 1990s in the East Asian “tigers”—Hong Kong, Singapore, South Korea, and Taiwan—did not yield a larger income gap. In other industrialized countries such as the United States, meanwhile, inequality is now rising, not falling.

    A wave of longitudinal studies tracking income and other metrics has helped flesh out the picture in developing countries like Indonesia, South Africa, India, and China. Those studies reveal growing inequality, which itself may stymie further growth, because poor people without access to good education cannot contribute to economies to their full potential.

    But a tour of emerging economies also shows that cultural factors influence how governments react, and whether citizens accept what seems to be an inevitable march toward greater inequality, or protest it.

    INDIA: HOW UNEQUAL? India illustrates the daunting task of measuring income and wealth in emerging economies. Half of all households get some income from agriculture, and most receive income from more than one source. A farmer might collect wages or receive payments from a cousin in the city, while a wage earner might also keep farm animals. To capture all earnings, surveyors for the national India Human Development Survey—which examines 41,554 households across the country—personally ask participants about 50 separate indicators of income.

    This herculean labor pays off, says Vanneman, a principal investigator on the survey, which is jointly administered by the University of Maryland and the National Council of Applied Economic Research in New Delhi. For example, one previously elusive indicator for India was the Gini coefficient, a common index of income inequality ranging from 0, in which everyone makes the same income, to 1, in which a single rich person would get a country's entire income. Government surveys based on expenditures and excluding income data had found figures in the 0.30s—below the level in the United States of 0.40. Such figures sparked “disbelief” among scholars, Vanneman notes: “Anybody who walks the streets of India cannot believe that inequality in India is as low as the common statistics suggest.”

    In 2010, the Indian survey found a Gini coefficient of 0.52—close to China's, which scholars most recently estimated at 0.55. At a time when attention is focused on inequality in the developed world, that's a sharp reminder that the worst inequalities are often in emerging economies (see map, pp. 820821). Inequality in high-income countries “still falls well below levels found in low- and middle-income countries,” Vanneman notes.

    CHINA: SURFING A RISING TIDE. In China, the market reforms of the past few decades have yielded some spectacular successes, giving rise to the lucky billionaires and also lifting the standard of living for the middle class. Between 2004 and 2009, the percentage of Chinese owning color TVs shot up from 80% to 96% and the percentage owning refrigerators swelled from 37% to 54%, according to surveys by sociologist Martin Whyte of Harvard University and colleagues at Peking University's Research Center for Contemporary China.

    Even so, the middle classes in China or India are “still rather poor within global comparisons,” Moran cautions. And the dramatic boost in inequality in China now presents a powerful challenge to the Kuznets curve. In a paper published online last month in the Proceedings of the National Academy of Sciences, sociologists Yu Xie and Xiang Zhou, both of the University of Michigan, Ann Arbor, plot China's rising income inequality, represented by the average Gini coefficients found by seven independent household surveys, against a Kuznets curve.

    In 1980, after the storms of the Cultural Revolution, China was well below the level of inequality predicted by the curve, with a Gini coefficient of merely 0.28. But in 2002, the country's Gini intersected the curve and then shot beyond it, Xie and Zhou found (see graph). The relationship between inequality and development in China looks more like a straight diagonal line than an inverted U, with no sign of flattening. Fearing a backlash, Chinese officials have suppressed publication of the Gini coefficient (Science, 31 May 2013, p. 1037) and challenged estimates of it that they consider high.

    But in fact Chinese appear remarkably tolerant of income gaps. The 2004 round of the survey by Whyte and colleagues polled 3267 Chinese on their attitudes as well as their income. Although respondents valued equality and believed the national income gap was excessive, only 30% supported redistributing wealth from rich to poor. Asked why people are poor, 61% said a lack of ability was an important cause, far higher than in any other country.

    Straying from the curve.

    Surveys taken during the last 10 years show that as China continues its rapid economic growth, its inequality continues to shoot upward, in contrast to what a Kuznets curve would predict.

    In the next round of the survey, done in 2009, the researchers found that despite the rising Gini, even fewer respondents viewed existing inequality as excessive. The findings challenge the notion that “rising income gaps are a major, or even the primary, threat to social order and political stability in China,” Whyte says. In a separate study, Xie, who also directs the Center for Social Research at Peking University, found that Chinese largely believe Deng's assertion that development and inequality are necessarily linked—even though economists have mostly disproven that statement.

    In 2006, Xie and colleagues polled residents in six provinces, asking them to separately rate levels of development and inequality in five countries: Brazil, China, Japan, Pakistan, and the United States. For level of development, respondents came up with rankings that closely mirrored U.N. estimates. But their guesses for inequality were way off. Instead of corresponding to Gini coefficients for the various countries, respondents believed that the most developed countries have the greatest inequality. Thus, many Chinese view inequality as the price of economic growth and accept it “as a fact of life,” Xie says. “That's why there's not as much resentment.”

    SOUTH AFRICA: ECHOES OF APARTHEID. Halfway around the world from China, South Africa faces similar economic challenges, but has a very different response, perhaps because the countries' starting points were so different. For decades under apartheid, black South Africans faced discriminatory barriers to mobility. As those barriers fell after 1994, expectations for a more level playing field soared. “This is the new South Africa,” says Murray Leibbrandt, an economist at the University of Cape Town and a principal investigator on the South African National Income Dynamics Study. “There was almost this irrationality that things were going to be much better moving forward.”

    By some measures, things did get better: As in China, absolute mobility rose, and most people are better off economically than they were 20 years ago. The share of people living below the poverty line—defined as $60 a month—fell from 57% in 2006 to 46% in 2011. Some expected reshuffling occurred, as skilled black Africans moved up the ladder and low-skilled whites moved down.

    But despite significant investment in education and a government vocally committed to fighting inequality, whites continued to earn more than blacks, and income became more concentrated in the top 10th. Between 1993 and 2008, overall income inequality actually increased, with the country's Gini coefficient rising from an already high 0.66 to a staggering 0.70, one of the highest in the world. Demand for highly skilled workers at the top increased, while black citizens at the bottom, burdened with poor education and health, remained relatively worse off. “The disadvantages of apartheid just linger,” Leibbrandt says.

    South Africans may be less accepting of inequality than the Chinese. In the past 5 years, millions of South Africans have taken to the streets to protest everything from high crime rates to a lack of affordable housing. About 91% say income differences are too large, and two-thirds say the country is going in the wrong direction, according to the South African Social Attitudes Survey.

    And yet, the hopefulness that dominated post-apartheid has not yet died. The survey also found that 42% of respondents believe that life will improve over the next 5 years. Given trends in absolute mobility, they are probably right.

    LATIN AMERICA: SEEKING THE SWEET SPOT. In Latin America, as in South Africa, a colonial past primed nations for inequality. Institutions established by colonial governments allowed elites to consolidate power and excluded indigenous and black populations from land ownership, education, and politics. Thus, the region has historically had very high Ginis: 0.59 for Brazil in 1998 and 0.55 for Mexico in 1996, according to a recent working paper from the World Bank.

    Added to this historically large gap between rich and poor is the fact that people born poor tend to stay poor. In Mexico, children of managers are a whopping 15.6 times more likely to hold on to their class status than to change it, according to data from the Mexican Social Mobility Surveys. Those are “near caste-like conditions,” wrote sociologist David Grusky of Stanford University in California and colleagues in a working paper last fall. In the United States, by contrast, children of managers are only 2.3 times more likely to end up in the same class. In every category except farming, Mexicans are less mobile than Americans. New York University sociologist Florencia Torche has found a similar lack of social mobility in Chile.

    Nevertheless, the gulf between income classes in Latin America has gradually narrowed, resulting in an impressive decrease in inequality across the region. In Mexico, the Gini coefficient fell 0.07 units between 1996 and 2010, to 0.48. In Brazil, the Gini coefficient dropped 0.05 units from 1998 to 2009, to 0.54. Throughout the 2000s, Ginis fell in 13 of 17 Latin America countries for which the World Bank has reliable data.

    An elderly man holds out his begging cup in bustling Hong Kong.


    So although the region is still battling inequality, such countries are now at something of a sweet spot, says Timothy Smeeding, an economist at the University of Wisconsin, Madison: As with the Asian “tigers” before them, the economy is growing, while inequality is falling. Even if it remains hard for people to move up relative to each other, many people are better off than before because absolute mobility is rising.

    GROWTH FOR ALL. Policy measures helped achieve such “pro-equity growth,” and scholars from countries like South Africa are studying how it was done. For example, the Brazilian government used grants to boost education. Average years of schooling shot up even among the poor. So when strong economic growth hit in the 1990s, marginalized citizens could get better jobs. From 2002 to 2009, the income of the bottom 10% grew at almost 7% a year, while that of the wealthiest 10% inched up by only 1.1% a year. The lesson for other developing nations, Leibbrandt notes, is the importance of job creation: Improvements in education and health may be good on their own, but they “don't narrow the income distribution until you get some feedback into the labor market.”

    Bucking theories put forward by proponents of the Kuznets curve, research now suggests that inequality may be a trap for developing countries. Far from boosting development, a large income gap can slow growth and stymie poverty reduction (see p. 851). In an entirely equal society, an increase in gross domestic product benefits everyone to the same degree, explains J. Humberto Lopez, an economist in the World Bank's Latin America and Caribbean region. In an unequal one, those at the top accumulate more income, leaving fewer dollars to boost households at the bottom. So to achieve the same reduction in poverty, highly unequal Brazil now needs to grow at least twice as much as a more equal country like Poland.

    Growth suffers as well; in unequal societies, talented people born into poverty have fewer opportunities to contribute. “It's a perfect storm,” Lopez says. “High inequality is bad for poverty, high inequality is bad for poverty reduction, and high inequality is not good for growth.”

    From Latin America's success at easing this trap and other cases, one thing now seems certain: Where inequality does decline, government involvement is key. Without substantial improvements in education and the social welfare system, “it's not natural” that inequality falls on its own, says Gan Li, an economist at Texas A&M University, College Station, and the Southwestern University of Finance and Economics in Chengdu, China.

    In China, now that Deng Xiaoping's prediction about some getting rich first has come true, economists hope it, too, will adopt a more “pro-poor” strategy.

    Over the past decade, China has boosted investment in social welfare programs, but it hasn't yet reached the spending necessary to begin leveling the playing field, Gan says. “China is at a crossroads,” he says. The government could follow the status quo, or it could “follow many other successful countries' paths—and change the system.”

  10. The Science of Inequality

    Tracking who climbs up—and who falls down—the ladder

    1. Jeffrey Mervis

    Researchers seek new ways to understand social mobility and opportunity in America

    Back in 1982, songwriter Billy Joel started off a hit music video with images of happy GIs returning to Allentown, Pennsylvania, at the end of World War II and taking advantage of a booming economy. As the years pass, however, the mood darkens.

    The song's message becomes clear when an apologetic foreman hands a pink slip to a young factory worker who's just ended his shift. There was a time, Joel croons, when “every child had a pretty good shot/To get at least as far as their old man got/But something happened on the way to that place.”

    The video pays homage to a once-thriving steel town battered by a spike in energy prices and the brief but painful recession in the early 1980s. It also questions the notion that talent and hard work can create a brighter future regardless of one's social standing at birth, suggesting that America is no longer the proverbial land of opportunity.

    Three decades later, in the wake of an even worse recession, President Barack Obama appears to have come to a similar, although more nuanced, conclusion. America faces a “dangerous and growing inequality and lack of upward mobility that has jeopardized middle-class America's basic bargain—that if you work hard, you have a chance to get ahead,” Obama warned in a December 2013 speech on the topic. It is, he said, “the defining challenge of our time.”

    The economists, sociologists, and demographers who study social mobility are thrilled that the president is shining a spotlight on their fields. At the same time, some grumble that Obama has muddied the water by conflating two different ideas—economic inequality and social, or intergenerational, mobility. The former is the gap in wealth between those in the penthouse and the poorhouse, which data show has reached high levels in the United States and is growing around the world (see pp. 826 and 838). The latter is whether children, as adults, “get at least as far as their old man got” on a ladder defined, not only by income but also by social factors including education, occupation, and where you live.

    Researchers say the data aren't good enough to support what seems to be accepted wisdom—that social mobility in the United States is declining. In fact, many think our understanding of this complex phenomenon is embarrassingly thin. “President Obama has made a big commitment to equalizing opportunity,” says sociologist David Grusky of Stanford University in California. “But he is making proclamations without any good evidence. Do we want to continue to do policy in the total, utter, complete blindness that the president now finds himself in?”

    To truly assess social mobility, researchers need a deep understanding of why some people are afforded an easier route to the good life than others. That means assessing complex variables such as education, occupation, health, neighborhood, social networks, and more. Researchers must also find a way to track large swaths of Americans over successive generations of parents and children, a costly proposition when done by the traditional mode of surveying a sample population.

    One new data set, based on an innovative use of U.S. tax data on a scale many times larger than has previously been done, illustrates the possibilities, showing for the first time how economic mobility varies by region of the country. The data and methods used wowed the field, and provide a starting point from which researchers might be able to tap into the records of other government agencies. But such studies will require the cooperation of those agencies and may not be easy to replicate.


    WHAT WE'VE LEARNED. Interest in social mobility has waxed and waned with economic cycles like the one that inspired the Allentown video. But tracking it has always been a challenge. Most of the recent data on U.S. social mobility comes from detailed surveys of relatively small samples of Americans. These studies have yielded some useful information. For example, they've shown how discrimination hampers economic mobility among African-Americans, how a college education can propel a rise through the economic ranks, and that a disturbingly large fraction of Americans—43% in one recent analysis—who grew up on the lower rungs remain there as adults. These studies have also allowed U.S. researchers to become world leaders in survey design and analysis, and other countries now emulate their methods.

    But many caveats still apply. “A lot of the data we have now [on social mobility] are essentially high-quality snapshots of individuals,” notes economist Ron Jarmin, who manages research and methodology for the U.S. Census Bureau, the government's de facto chief statistical agency. So although researchers have managed to pull out some results on social mobility, the survey data “are not intended or designed for longitudinal analysis,” Jarmin says. Without such analysis, it's impossible for researchers to say whether mobility is changing over time, and why.


    For a related video on social mobility, see

    That void leaves policymakers at a loss in knowing which factors to address—parental education, occupational status, social standing, housing, health, and so on—if they want to create a more level playing field.

    WHAT'S ON FILE. Given limited resources, researchers say the best way to overcome these shortcomings is to supplement survey results with so-called administrative records. Government agencies are awash in data collected for other purposes that could inform studies of mobility. A student loan application, for example, includes information on income, siblings, parental level of education, high school record, neighborhood, and other bits of sociodemographic information. Several Western European countries link such records together and allow researchers to access them. That's one reason we know a lot more about social mobility in, say, Denmark and Sweden than in the United States.

    No such massive, linked data sets exist in the United States. But last summer, in a study that has impressed their colleagues, a team of economists led by Raj Chetty of Harvard University and Emmanuel Saez of the University of California, Berkeley, took an important step in creating one.

    The study, put up on a website in January, showed for the first time a link between children's hometowns and whether they climb or fall down the economic ladder as compared with their parents. One metric they used calculated the chances that a child born in the early 1980s (as it happens, when Joel wrote his hit song) into a family in the lowest fifth of the income distribution would jump to the top fifth by age 30. They found striking geographical differences. For example, in San Jose, California, nearly 13% made the leap upward, in contrast with only 4.4% of children from Charlotte, North Carolina. Allentown fell in the middle range, with a score of 8.3%.

    The findings drew global media attention. But what created a buzz among mobility researchers was how the research team was able to gain direct access to previously unavailable U.S. tax records. Most researchers aren't allowed to handle tax data themselves. Instead, they submit their program for examining such data to the IRS, where agency employees run the program and ship researchers the output. Chetty and Saez, in contrast, effectively became part of the IRS workforce, submitting to training, background checks, and fingerprinting before being allowed to run the data and tweak their models themselves, according to IRS officials (

    In this way, Chetty and Saez created a database of children born in the early 1980s. They then followed the children into young adulthood and obtained their incomes at age 30. This data is now part of a larger database covering more than 20 countries, called the World Top Incomes Database, which French economist Thomas Piketty and colleagues have created to study inequality (see p. 826).

    Researchers say that Chetty and Saez's data, if linked to administrative records at other U.S. agencies, could yield “a gold mine of information on intergenerational mobility” that researchers never thought would be available. “If you would have asked me a couple of years ago, I would have said that was a pipe dream,” says Gary Solon, an economics professor at Michigan State University in East Lansing.

    For all its richness, however, the study also comes with notable limitations. One is that a person's economic profile is still being formed at age 30. Collecting data on them at age 40 would yield “a more accurate assessment,” Solon says. That could happen only if the IRS allows researchers the same access 10 years from now that it gave the Chetty-Saez team.

    The study also captures a cohort of Americans at a particular time. Immigrants who arrived after the first snapshot of people was taken in the 1980s aren't included; people who don't earn taxable income or lack valid Social Security numbers are also omitted. In addition, the IRS data lacks information on race and ethnicity, which may be correlated with mobility rates.

    But researchers see promise in Chetty and Saez's approach. “They linked tax records over time and showed some really cool stuff,” Jarmin notes. “But what's really exciting is that they have also created a core infrastructure that will allow researchers to link to many other data sets that already exist.”

    When linked to administrative records, the usefulness of surveys by the Census Bureau and others “grows by orders of magnitude,” Jarmin says. Linking Chetty's data on income to the Census Bureau's demographic and housing data, for example, could create a picture of quality of life—a rich, multidimensional view that goes well beyond simple income.

    Of course, many hurdles remain before such linked data sets are common. Few agencies are set up to collaborate with other agencies, much less with outside researchers. And agencies would have to remain vigilant against any breaches in confidentiality that could lead to the identification of individuals or companies.

    All the same, there are hints that the government is eager to maximize the value of the data it collects. In February, the White House Office of Management and Budget urged agencies to make better use of their troves of economic and demographic data—so long as their actions don't jeopardize privacy.

    If the data were connected, mobility researchers would be on their way to a much better understanding of who rises and falls in American society—and why. It's definitely a step in the right direction, says the Census Bureau's Jarmin. “If I ran the world,” he says of linking government and survey data, “that's what I'd do.”