The Nobel Memorial Prize in Economic Sciences was awarded Monday to three economists who have studied why some countries are rich and others poor and have documented that freer, open societies are more likely to prosper.

The work by Daron Acemoglu, Simon Johnson and James A. Robinson “demonstrated the importance of societal institutions for a country’s prosperity,” the Nobel committee of the Royal Swedish Academy of Sciences said at the announcement in Stockholm.

Acemoglu and Johnson work at the Massachusetts Institute of Technology, while Robinson does his research at the University of Chicago.

Jakob Svensson, chair of the Committee for the Prize in Economic Sciences, said their analysis has provided “a much deeper understanding of the root causes of why countries fail or succeed.”

Reached by the academy in Athens, Greece, where he was to speak at a conference, the Turkish-born Acemoglu, 57, said he was astonished by the award. “You never expect something like this,” he said.

– The Associated Press