Wall Street is about to get a new boss. Jerome Powell's term as Fed Chair ends on May 15, and the betting line points to Kevin Warsh taking the reins. That kind of leadership change at the world's most powerful central bank tends to make investors nervous—and history says they might be right to sweat.

But here's the twist: the person in the chair may matter a lot less than the economic mess they inherit.

The Replacement Illusion

Dr. Dejan Kovač, a Harvard postdoc fellow, crunched the numbers on every Fed transition over the last 50 years—from Burns to Miller in 1978 all the way to Powell in 2018. The headline finding is stark: in the year following a new chair's arrival, stocks underperform by an average of 7.7 percentage points relative to a typical year.

That sounds like a strong case for 'sell in May and go away' if you're worried about Warsh. But Kovač dug deeper. He controlled for things like inflation (CPI), the Fed funds rate, recession risk, market volatility (VIX), and the shape of the yield curve. Once those factors were in the model, the 'Fed Chair penalty' shrank to just 1.8 percentage points.

"Once we include these controls, the estimated effect drops significantly — from about −7.7 percentage points to roughly −1.8 percentage points," Kovač noted.

In other words, the massive drawdowns that happened when Alan Greenspan took over in 1987 or Powell in 2018 weren't really about the new boss. They were about lousy timing—like late-cycle tightening or external shocks. The chair was just the guy in the hot seat when the economy caught fire.

Testing the Chair

Still, not everyone is ready to dismiss the personality factor. Mark Hackett, Chief Market Strategist at Nationwide, points out that markets have a habit of 'testing' new Fed chairs. Using data back to 1930, he found that the S&P 500 typically drops about 9% within six months of a new chair taking over.

"Historically, these indicators have carried meaningful weight," Hackett wrote, noting an 87% positive track record for the 'January Barometer' in 2026. But he also warns that markets have "tended to 'test' new Fed chairs, reflecting the uncertainty that often surrounds changes in policy tone, communication style, and the central bank's decision-making approach."

Hackett is quick to add that "historical patterns should be viewed as context, not prophecy." And Kovač argues that today's market is far more sophisticated than in decades past.

"Wall Street has already studied every major crisis. The mechanisms are known. The playbooks are known. So what do traders do? They hedge in advance," Kovač said.

He points to the market's muted reaction to the Warsh news as evidence. "That is why we are not seeing identical reactions to oil shocks, AI hype, or geopolitical risk compared to previous decades. Because everyone is running the same analysis. The market is not surprised anymore."

So yes, a new Fed chair historically comes with a hangover. But the real driver may be the economy's underlying health—not the nameplate on the door. For investors, that means watching inflation and recession signals might be more useful than obsessing over Warsh's first press conference.