Nobel laureate Robert Shiller suggests a self-fulfilling is prophecy unfolding on Wall Street that could ultimately derail the longest bull market in history.
According to the Yale University economics professor, growing worries about a recession could make it come sooner — even if there isn't a specific event to spark it.
"A lot of people have that on their mind, and they think it's got to turn soon. I'm kind of with that. You know, if people think that, they're going to make it happen," Shiller said Wednesday on CNBC's "Trading Nation."
Shiller, who's known for his behavioral finance research, estimates there's about a 50 percent chance the economy will tip into a recession within 18 months.
He's not sure what how long it could last or the magnitude. However, he isn't ruling out a Trump-related event — even though the president has been an integral part of the economic narrative behind the bull run.
"People who are good storytellers — like Donald J. Trump is a brilliant storyteller — they tend to rise in our economy," Shiller said. "He models a general public support for business, cuts profits taxes — what more can you ask?"
But if Trump loses his base because of his legal woes, Shiller believes that could usher in trouble.
He also refers to the growing budget deficit as an ominous economic issue. It grew to $913 billion for the fiscal year ending in January. That's 77 percent higher than the previous year.
And it's expected to get worse. The Congressional Budget Office projects yearly budget shortfalls will surpass $1 trillion beginning in 2022.
"That attention to public debt has waxed and waned throughout history," Shiller said. "It seems like the public is OK with it for now. But I think in the back of their minds they're not so sure."
