STOCKHOLM - American economists Alvin E. Roth and Lloyd S. Shapley shared 2012 Nobel Prize for Economics, announced Staffan Normark, Permanent Secretary of the Royal Swedish Academy of Sciences in Stockholm on Monday.

The duo won the award "for the theory of stable allocations and the practice of market design," said Normark.

"This year's prize is awarded for an outstanding example of economic engineering," said the academy in a statement.

The two researchers worked independently, but their empirical investigations, experiments and practical design have generated a flourishing field of research and improved the performance of many markets, the academy added.

Roth is from Harvard University and Shapley from University of California, USA. The two laureates will equally share the 8 million Swedish kronor (about $1 million) prize.

The economics award, established in 1968 and officially called The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, is the last of the six prizes announced this year. It is not part of the original crop of Nobel Prizes set out in Alfred Nobel's 1895 will.

Sixty-nine Laureates had been awarded the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel between 1901 and 2011.

The economic prize will be issued on December 10 the day Nobel died together with prizes in Physiology or Medicine, Physics, Chemistry and Literature in Stockholm.