‘Black Swan’ investor warns the ‘greatest bubble in human history’ is about to pop and stocks could lose more than half their value

Mark Spitznagel, cofounder and chief investment officer of the hedge fund Universa Investments, has frequently sounded the alarm about bubbles popping and other extreme market events.

In an interview with the Wall Street Journal , the long-time associate of The Black Swan author Nassim Nicholas Taleb said a severe crash is on the way and stocks could lose more than half their value, while acknowledging that his latest warning should come as no surprise.

"I think we’re on the way to something really, really bad—but of course I’d say that , " Spitznagel said.

His hedge fund specializes in tail-risk hedging , a strategy that seeks to prevent losses from unforeseeable and unlikely economic catastrophes, also known as "black swans."

He had famously made astronomical gains on such events, including the COVID-19 pandemic, and more recently has warned about U.S. debt and the " greatest credit bubble in human history. "

Even as stocks have come well off recent highs, with the S&P 500 suffering its worst week since April , Spitznagel expects the market rally to continue for months and get wilder because the "Goldilocks phase" of slowing inflation and rate cuts from the Federal Reserve will stoke bets that markets will continue running higher.

But he also warned Fed rate cuts are often the opening signal for severe market reversals, telling the Journal that "You don’t feel like a fool for making a bearish argument."

Spitznagel sees parallels between today and the dot-com bust but thinks the selloff that's coming will be even worse than that. That's because market extremes now represent the "greatest bubble in human history," he added.

With U.S. debt already at historic levels , the federal government will have less capacity to respond, and the economy could enter a recession by the end of this year, he predicted.

Spitznagel's latest comments echo what he told Fortune's Will Daniel in April , when he said investors’ positive sentiment alone can’t carry markets higher indefinitely and that higher rates are weighing on the economy.

“The Fed did a lot. And now it’s sort of jawboning its way out of it. But it can’t take back what it did,” he said. “Markets follow fundamentals at the end of the day, but you can have these little Goldilocks zones where it can get sort of untethered.”

Fed Chairman Jerome Powell and other central banks have hinted in recent days that inflation is finally coming under control and that rate cuts may be coming soon, with markets widely seeing the first one in September.

But Spitznagel said in April that fallout from the “the fastest, greatest tightening ever, by some regards, into the greatest credit bubble of human history” can’t be avoided, adding "That’s when things are going to be really bad—and at that point, it’s probably also too late to get out."

This story was originally featured on Fortune.com