Nobel Laureate economist Robert Shiller says the ongoing stock market rally could go on for months if not longer and the reason is an emotional high thanks to President Donald Trump.

“I put Trump as the primary cause of the recent strength in the market,” Shiller said on CNBC’s “Trading Nation” program. “He’s a motivational speaker. We’ve never had a motivational speaker president before. He knows how to create animal spirits.”

Shiller, a Yale economics professor who wont the Nobel Prize in 2013, correctly predicted the stock market crash of 2000 and the crash resulting from the housing bubble of 2006. He wrote a new book this year called “Narrative Economics,” which discusses the idea that popular stories, psychology and even worries of a recession can end up being self-fulfilling prophecies.

“It may not be so logical. It may be more, as I said, of animal spirits,” he said. “This is an emotion that you feel at a certain time that you sense you see in other people. So when you see other people feeling confident about the market, you feel more confident yourself.”

While Shiller says a strong economy is important for big markets gains, it could come at magnified costs down the road.

The Shiller PE Ratio, otherwise known as CAPE, shows the price-to-earnings ratio based on average inflation-adjusted earnings over the past decade, is currently at a bad level.

“The ratio is around 30 now which is quite high by historical standards,” said Shiller. “On the other hand, if you go back to 1999 and 2000, the ratio got up to 44. So it was about 50% higher than it is now. Eventually, it gets out of whack.”

However, for 2020, Shiller is bullish on the market’s outlook. He also thinks there’s a good chance of Trump getting reelected, and said a recession is likely years away.

“We might see a continuation of the Trump boom for a while despite the impeachment,” Shiller said. “I could easily see that happening.”