Americans Leonid Hurwicz, Eric S. Maskin and Roger B. Myerson won the Nobel prize in economics on Monday for developing a theory that helps explain how incentives and private information affect the functioning of markets.

Hurwicz, 90, is the oldest Nobel winner ever, according to the academy. "I really didn't expect it," said the Moscow-born researcher, an emeritus economics professor at the University of Minnesota in Minneapolis.

The three winners "laid the foundations of mechanism design theory," which plays a central role in contemporary economics and political science, the Royal Swedish Academy of Sciences said.

Essentially, the three men, starting in 1960 with Hurwicz, studied how game theory can help determine the best, most efficient method for allocating resources, the academy said.

Their research has helped explain decision-making procedures involved in economic transactions including, for example, what insurance polices will provide the best coverage without inviting misuse.

It has been used in everything from negotiations over labor issues to the auctioning of government bonds and has helped countries and companies better understand how markets function even when conditions are rocky.

Hurwicz told reporters he was surprised to have won the award.

"There were times when other people said I was on the short list, but as time passed and nothing happened I didn't expect the recognition would come because people who were familiar with my work were slowly dying off," he said.

Maskin, 56, is professor at the Institute for Advanced Study at Princeton, New Jersey; and Myerson, 56, is a professor at the University of Chicago in Illinois.