Jamie Dimon sees ‘gung-ho’ attitude and ‘exuberance’ in markets—just like 1972, 1986, 2000 and 2007. Uh Oh.

The deals are flowing, bankers are busy, sponsors are spending. The clients aren’t hesitating. “It’s gung-ho, folks,” Jamie Dimon told the Bernstein Strategic Decisions Conference on May 27. Then came the footnote that should make every CFO, fund manager, and investor think twice. “There’s a lot of exuberance out there,” Dimon continued. “But it was in 1972, 1986, 2000, 2007. That doesn’t give me comfort.” Four years, and four peaks. Four disasters waiting just around the corner from the party. Nobody has a better real-time read on the global economy than the chairman and CEO of JPMorganChase, the largest bank in the United States with nearly $5 trillion in assets. When Dimon says M&A is tracking toward the best year in recent memory, that equity capital markets activity (i.e., initial public offerings) is set to be “huge,” and that corporate clients are broadly eager to transact, he’s watching the flow of money, deals and risk appetite from his perch as the mayor of Wall Street. In the week since Dimon uttered his remarks, the $956 billion-valued Anthropic confidentially filed for an IPO, and Goldman Sachs equity analysts projected a record $225 billion in IPOs this year. (SpaceX has officially filed to go public, leaving OpenAI as the other major listing yet to drop). Fortune has heard this word before It’s unclear if Dimon’s historical callback was intentional. He reached for one very particular word: exuberance, the same word Alan Greenspan used in December 1996 when he remarked on “irrational exuberance” in equity markets. Here’s something worth noting before we go further: Fortune has a direct, if largely forgotten, connection to the vocabulary Dimon just deployed. In March 1959, a young economist named Alan Greenspan (the very same) was quoted in a Fortune article using the phrase “over-exuberance” to describe financial market sentiment. Nea