Date October 11, 2021
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Brown Class of 1991 Ph.D. graduate wins Nobel Prize in Economic Sciences

Guido Imbens, a Stanford University economist who received his Ph.D. from Brown in 1991, was recognized for his major role in analyzing causal relationships in the social sciences.

PROVIDENCE, R.I. [Brown University] — Guido Imbens, a Stanford University economist who earned his Ph.D. from Brown University in 1991, is one of three recipients of the 2021 Nobel Prize in Economic Sciences, the Royal Swedish Academy of Sciences announced on Monday, Oct. 11, in a live-streamed presentation

Imbens and colleague Joshua Angrist, an economist at the Massachusetts Institute of Technology, were awarded the prize in recognition of their methodological contributions to the analysis of causal relationships, according to the academy. The pair split the prize with David Card of the University of California, Berkeley, whose empirical contributions to labor economics helped launch a new era of natural experiments across the social sciences.

As a Nobel laureate, Imbens will receive a gold medal, a diploma and $286,250 — a quarter of the $1,145,000 economics prize.

Peter Fredriksson, chair of the Royal Swedish Academy’s economic sciences committee and a professor of economics at Uppsala University, said the three scholars’ work has revealed ways in which natural experiments — that is, experiments that divide people into treatment and control groups naturally, without any scientific intervention — can answer important questions for society.

“Joshua Angrist and Guido Imbens have clarified exactly what conclusions about cause and effect can be drawn from natural experiments,” Fredriksson said. “Their framework for estimation, validation and interpretation has been widely adopted in applied work. The combined contributions of the laureates have completely reshaped empirical work in the economic sciences, and therefore our ability to answer causal questions of great importance to us all has improved tremendously.”

In 1996, Imbens and Angrist outlined a highly influential framework for causal inference in the Journal of the American Statistical Association. Their framework has been cited in scientific studies more than 6,000 times, and it has enabled hundreds of experiments exploring causal relationships — such as relationships between income and health, immigration policy and the labor market, and lockdowns and the spread of infection.

Imbens, who spoke on the phone with academy leaders and reporters during the presentation, said he received a phone call with the exciting news while still asleep in California.

“It was a little after 2 in the morning here,” he said. “The whole house was asleep; we’d had a busy weekend. I was just absolutely stunned to get a telephone call, and then I was absolutely thrilled to hear the news.”

The economist said he was particularly excited to share the award with Angrist and Card, both “good friends of mine.” Angrist, he said, had been the best man at his wedding.

Asked if he had advice for aspiring economists, Imbens encouraged young people to consider the profession for its flexibility and potential societal impact.

“Economics is a really interesting discipline these days, where you can look at so many questions and... in so many different ways,” he said. “And so for young people thinking about a career in economics, I think that’s a great choice. Economics tends to be a good discipline for allowing people to pursue questions that are quite broad... areas where economists do useful work, both in policy and in many cases in private industry.” 

Imbens’ journey to Brown

Imbens was born in Eindhoven in the Netherlands, and after taking undergraduate courses at Erasmus University Rotterdam, he went to the University of Hull in the United Kingdom to pursue a master’s degree. There, alongside fellow Dutch graduate student Wilbert van der Klaauw, Imbens worked with the economist Tony Lancaster, who said he quickly saw the young student’s talent for logic and statistics.

Lancaster said he, van der Klaauw and Imbens became friends as well as colleagues — and when the former accepted a faculty position at Brown in 1986, the two Dutch master’s degree graduates joined him in Providence to pursue Ph.D.s. Lancaster and Imbens collaborated on a research project on the econometrics of homelessness in New York, raising important questions about how to engage in research on people who don’t have addresses or phone numbers and are thus more difficult to reach.

“He’s just a very clever young man, perhaps the cleverest I’ve known,” said Lancaster, now a Brown professor emeritus of economics. “Guido’s hobby as a boy was playing simultaneous blindfold chess in the local park. I always, wisely, declined to give him a game. Think of the loss of face.”

Rajiv Vohra, a professor of economics at Brown, said Lancaster’s mentorship helped put Imbens on the fast track to success.

“It is to Tony that we owe the good fortune of having Guido as a student, and it was Tony who mentored him in those formative years,” Vohra said. “There's a wonderful story about Tony's conversation with the department's placement director when Guido was on the market [as he neared Ph.D. completion]. Asked where he thought Guido could get placed, Tony replied, ‘anywhere.’”

“Anywhere,” Vohra noted, turned out to be Harvard University, where Imbens accepted a teaching position after graduating from Brown. From Harvard, Imbens moved to the University of California, Los Angeles, U.C. Berkeley and eventually Stanford University, where he is now a professor of economics and applied econometrics.

In 2017, Brown awarded Imbens the Horace Mann Medal — an annual honor to a Brown Graduate School graduate who has made important contributions in their field — in recognition of his important contributions to the field of economics.

Imbens is not the first Brown-affiliated scholar to receive a Nobel Prize, with two professors on the Brown faculty at the time of their awards having received the honor. In 2016, Professor of Physics J. Michael Kosterlitz won the Nobel Prize in physics "for theoretical discoveries of topological phase transitions and topological phases of matter.” He joined Leon Cooper, a professor of physics, who won the prize in 1972 for developing a theory of superconductivity, the ability of some materials to conduct electricity with zero resistance.