It's a mystery to me: Nobel Prize winner Richard Thaler on record markets

University of Chicago professor Richard Thaler may have won the Nobel Economics Prize on Monday for his work on behavioural economics, but the behaviour of investors has him stumped.

Thaler said on Tuesday he is puzzled by the steady rise of global stock markets in recent years, even as many countries are gripped by political and social drama.

"It's a mystery to me. That, and the unbelievably low volatility in a time of massive global uncertainty seems mysterious to me," Thaler said in a phone interview from his Chicago apartment.

Thaler also said his field could do more to research how human psychology affects things like inflation or interest rates.

"Behavioural economists have not invested as much in macro as I would like," he said.

Thaler spoke as US stocks flirted with new record highs on Tuesday. The S&P 500 index is up roughly 14 per cent for the year amid optimism about the economy and corporate profits.

Thaler's humble tone stood in contrast to the wide acclaim he received Monday when the 72-year-old was awarded the 9 million Swedish crown ($1.1 million) prize for his work on how human nature affects supposedly rational markets.

His research showed how traits such as lack of self-control and fear of loss can prompt decisions that have bad long-term outcomes.

Thaler's work has been applied in many areas such as auto-enrolling workers into retirement savings plans and adjusting their investments according to their age.

Thaler also has done well outside of the academic world, as part-owner of an $8 billion investment management firm in California, Fuller & Thaler Asset Management. It aims to practice financial theory such as looking for cases where other investors over-reacted and sold off too much of a stock based on bad news.

The firm often focuses on small-cap companies, with market values of $3 billion or less, because there are fewer competing investors and thus more opportunities for gains, he said.

Thaler made a short appearance in the Academy Award-winning 2015 film The Big Short, explaining the so-called "hot-hand fallacy" in which past success is expected to also warrant success in the future, with pop star Selena Gomez.

Thaler said he rejected an early version of the script, wanting to be sure he spoke accurately for film audiences.

"If I was going to make a fool of myself in a movie at least I'd get the economics right," Thaler said.