Famed investor Jeremy Grantham on Thursday reiterated his warning that Wall Street is in a bubble as individual traders get “carried away.”

“They’re becoming euphoric … They’re borrowing money. They’re trading more shares,” Grantham, co-founder and chief investment strategist at Grantham, Mayo, & van Otterloo told CNBC’s “Squawk Box Asia” on Thursday.

In recent months, Grantham has warned that the massive runs on Wall Street are turning into an “epic bubble.” On Thursday, Grantham pointed to the number of over-the-counter shares traded since last February rocketing to 280 million shares in November and quadrupling to 1.15 trillion shares in December.

“We have very seldom seen levels of investor euphoria like this,” he said, referring to individual investor speculation, rather than institutional.

Grantham said individual investors “are throwing their hearts and souls into it and putting all their cash reserves into the market.” He pointed to the recent rally in bitcoin as well as the proliferation of special purpose acquisition companies (SPACs).

SPACs have no commercial operations and are established solely to raise capital from investors, for the purpose of acquiring one or more operating businesses. Grantham described SPACs, which are sometimes referred to as blank-check companies, as “an invitation to give me your money and I’ll let you know one day what I’m going to do with it.”

Grantham cautioned that there has “never been a great bull market that ended in this kind of bubble that did not decline by at least 50%.” But he said the catalyst that triggers that drop is “much more difficult” to predict.

“It’s entitled to go tomorrow if you look at all the signs … As soon as the new president gets settled in, that would be a perfectly good time for the bubble to start deflating,” he said.

But, assuming that the world “gets lucky” and the bubble carries on, with people getting their second vaccine doses, he said it would still hit investors at some point that the world “really hasn’t changed.”

“It has all the problems it had a year ago. Global trade is declining as a ratio … global growth is getting steadily slower and slower for the last few decades. And the population profile is busting – there are fewer baby cohorts … these are all very bad for growth,” Grantham said.

Grantham said he prefers emerging market assets over U.S. markets and also likes cash and American venture capital.

He said emerging markets are “respectably priced” compared with overpriced U.S. markets. Although emerging markets would likely fall with U.S. markets, Grantham said the crash would not be as bad because they are cheaper.

“Emerging markets in many ways are the growth that’s left in the system. They will guarantee to grow faster than the developed countries … they’re much cheaper, they haven’t been beat up, they don’t have as much speculative excess. They’re a respectable investment,” he said. “And I would certainly prefer cash to American equities.”

Grantham was also positive on American venture capital, which he called the “most virile part” of the U.S. capitalist system.

“Most of what happens these days in America is exceptionally bad. But the venture capital is truly exceptional, the U.S. venture capital industry has always been dominant, has always been the best,” he said. “And I’m very happy to put my money there. It has the highest return. In the long run, it’s outperformed equities.”