Three U.S-based economists won the 2021 Nobel prize for economics on Monday for pioneering research on the labor market impacts of minimum wage, immigration and education, and for creating the scientific framework to allow conclusions to be drawn from such studies that can’t use traditional methodology.

Canadian-born David Card of the University of California at Berkeley was awarded one half of the prize, while the other half was shared by Joshua Angrist from the Massachusetts Institute of Technology and Dutch-born Guido Imbens, 58, from Stanford University.

The Royal Swedish Academy of Sciences said the three have “completely reshaped empirical work in the economic sciences.”

“Card’s studies of core questions for society and Angrist and Imbens’ methodological contributions have shown that natural experiments are a rich source of knowledge,” said Peter Fredriksson, chair of the Economic Sciences Committee. “Their research has substantially improved our ability to answer key causal questions, which has been of great benefit for society.” 

Card worked on research that used restaurants in New Jersey and in eastern Pennsylvania to measure the effects of increasing the minimum wage. He and his late research partner Alan Krueger found that an increase in the hourly minimum wage did not affect employment, challenging conventional wisdom which held that an increase in minimum wage will lead to less hiring.

Card’s work also challenged another commonly held idea, that immigrants depress wages for native-born workers. He found that incomes of the native-born can benefit from new immigration, while it is earlier immigrants who are at risk of being negatively affected.

Angrist and Imbens won their half of the award for working out the methodological issues that enable economists to draw solid conclusions about cause and effect even where they cannot carry out studies according to strict scientific methods.

Speaking by phone from his home in Massachusetts, Imbens told reporters gathered for the announcement that he had been asleep when the call came.

“The whole house was asleep, we had a busy weekend.” said Imbens. “I was absolutely thrilled to hear the news.”

He said he was especially thrilled for Angrist, who was best man at his wedding. 

Unlike the other Nobel prizes, the economics award wasn’t established in the will of Alfred Nobel but by the Swedish central bank in his memory in 1968, with the first winner selected a year later. It is the last prize announced each year. 

Last week, the 2021 Nobel Peace Prize was awarded to journalists Maria Ressa of the Philippines and Dmitry Muratov of Russia for their fight for freedom of expression in countries where reporters have faced persistent attacks, harassment and even murder. 

Ressa was the only woman honored this year in any category. 

The Nobel Prize for literature was awarded to U.K.-based Tanzanian writer Abdulrazak Gurnah, who was recognized for his “uncompromising and compassionate penetration of the effects of colonialism and the fate of the refugee.”

 The prize for physiology or medicine went to Americans David Julius and Ardem Patapoutian for their discoveries into how the human body perceives temperature and touch. 

Three scientists won the physics prize for work that found order in seeming disorder, helping to explain and predict complex forces of nature, including expanding our understanding of climate change. 

Benjamin List and David W.C. MacMillan won the chemistry prize for finding an easier and environmentally cleaner way to build molecules that can be used to make compounds, including medicines and pesticides.