William Nordhaus and Paul Romer won the 2018 Nobel Economics Prize for integrating climate change and technological innovation into macroeconomic analysis, the Royal Swedish Academy of Sciences said on Monday.

"Their findings have significantly broadened the scope of economic analysis by constructing models that explain how the market economy interacts with nature and knowledge," the academy said in statement.

The Nobel economics prize was created by the Swedish central bank "in memory of Alfred Nobel" and first awarded in 1969, unlike the other prizes which were created in his last will and testament and first awarded in 1901.

As with the other Nobels, nominations and deliberations are kept secret for 50 years, so it´s nearly impossible to know which way the prize committee is leaning each year.

"From a historical perspective, there are about as many conservative as liberal economists in recent years and the trend has been for diversification: the range of fields of research that have been honoured has been more vast, the choice of laureates has been more eclectic," economist Gabriel Soderberg of Sweden´s Uppsala University told AFP.

Last year the prize went to US economist Richard Thaler, a co-founder of the so-called "nudge" theory, which demonstrates how people can be persuaded to make decisions that leave them healthier and happier.

"The heart of the Nobel prizes are the awards for science, peace and literature. The economics prize is not formally a Nobel prize ," Soderberg said.

That fact may make "the jury more attentive to public opinion, a little more sensitive to the way in which the laureate will be received," he said.

This is why "societal questions are reflected in the prize. The issue of climate change is very important right now and (for this reason) William Nordhaus could be honoured," he said.

Nordhaus, a Yale University professor known for his research on the economic consequences of global warming, bears two of the typical characteristics of a Nobel economics laureate: he´s a man, and he´s American, like 70 per cent of previous prizewinners. At 77, he´s a decade older than the average winner.