• David Rosenberg pointed to the exuberance for AI, which has sparked a "raging bull market."
  • The "speculative mania" carrying the stock market could soon end, he warned.
The stock market is flashing the same warning signs of "speculative mania" that preceded the crashes of 2008 and 2000, according to economist David Rosenberg.

The Rosenberg Research president — who called the 2008 recession and who's been a vocal bear on Wall Street amid the latest market rally — pointed to the "raging bull market" that's taken off in stocks, with the S&P 500 surpassing the 5,000 mark for the first time ever last week.

The benchmark index has soared around 22% from its low in October last year, clearing the official threshold for a bull market. The index has also gained for the last five weeks and has been up for 14 of the last 15 weeks — a winning streak that hasn't been seen since the early 1970s.  

But the stellar gains are a double-edged sword for investors, as the market looks dangerously similar to the environment prior to the dot-com and 2008 crashes, Rosenberg wrote in a note on Monday. 

Other Wall Street strategists have warned of the parallels between today's market and similar stock booms in the past. The hype for artificial intelligence pushed the Magnificent Seven stocks to dominate most of the S&P 500's gains last year, and a major price correction is on the way as valuations soar to unsustainable levels, Richard Bernstein Advisors said in an October 2023 note. 

"This is the problem when a  group of mega cap 'concept' stocks trade at double the multiple of the rest of the market. The lesson is that (i) the higher they are, the harder they fall, and (ii) there are dangers when too much growth gets priced in," Rosenberg said. "Being real in an economic sense does not mean we have not entered a realm of excessive exuberance when it comes to the financial markets," he added, referring to the hype surrounding AI.

The outlook for stocks is also shadowed by an uncertain economic picture. Geopolitical risks, recession risk, and the risk that the Fed will disappoint investors hoping for rate cuts aren't being priced into markets at the moment, Rosenberg added.

Rosenberg has warned investors to tread carefully before, given the slew of risks he sees ahead for markets. Previously, he said that the S&P 500 looked "eerily similar" to 2022, the year the index plunged 20%. That's partly because a recession that "few see and few are positioned for" is coming for the economy, he wrote in a post on LinkedIn last month.