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Few economists could honestly describe themselves as life-savers. Professor Al Roth from Stanford University in the United States doesn't describe himself that way either. But he is. His application of a kind of mathematics developed as a thought-experiment 50 years ago is keeping hundreds - perhaps thousands - of people alive by enabling kidney transplants which would not otherwise have happened.

Al Roth was awarded the 2012 Nobel Memorial Prize in Economic Sciences this week. He shared it with Lloyd Shapley, the man behind that half-a-century-old thought experiment. In this week’s edition of More or Less Professor Al Roth tells Tim Harford how Shapley’s insights, and his own later – life-saving – work.

(Image: Two surgeons perform a kidney transplant, Credit: Getty Images)