Last week alone saw several CEOs of high-profile companies lose their jobs, starting with Adam Neumann, the charismatic but controversial founder who led WeWork into years of manic growth—and then into a troubled IPO candidacy. That news preceded WeWork’s announcement Monday it would withdraw its IPO filing.

Other departures in the past week include Kevin Burns of Juul, which is battling lawsuits, regulatory crackdowns, and reports of horrifying lung illnesses; Devin Wenig of eBay, which is facing pressure from activist investors to break the company apart; Ramesh Tainwala of Samsonite, amid resume-padding allegations; and John Flint of HSBC, following an uneasy 18-month stint.

That’s a lot of revolving doors churning in executive suites. But last week was no aberration. If anything, it marks an acceleration of a trend that has been evident through 2019.

Earlier in September, Hiroto Saikawa was forced out as CEO of Nissan after improperly adding to his compensation. Meanwhile, another top job at an international automaker hangs in the balance. Last week, German prosecutors charged Volkswagen CEO Herbert Diess with market manipulation.

August, too, was a something of a frenzied month for CEO turnover. According to Challenger, Gray & Christmas, August saw 159 CEO exits, the highest figure since the executive outplacement firm began gathering data in 2003. (The company has not yet compiled data for September.)

Those August exits include Overstock founder and lightning-rod-in-chief Patrick Byrne, who stepped down amid his involvement in a FBI Russian-espionage probe and controversial comments he made about the “deep state;”  as well as Dion Weisler of HP; Rupert Hogg of Cathay Pacific; Scott Wagner of GoDaddy; Karl Roessner of E*Trade; and Jeff Cain of Crossfit.

And a sampling of departing CEOs in previous months includes Wells Fargo’s Tim Sloan (the second CEO ousted in the wake of the bank’s 2015 fake-accounts scandal), whose replacement was finally announced Friday; Norwegian Air’s Bjorn Kjos; Zillow’s Spencer Rascoff; and REI’s Jerry Stritzke.

In fact, Challenger’s CEO data shows 1,009 CEO changes in the first eight months of 2018, a 15% increase from a year earlier and on track to be the biggest year for CEO turnover in at least 17 years. The pace of churn exceeds that of the Great Recession. Even with U.S. stock indexes near record highs and the economy expanding, more company leaders are leaving their jobs.

What’s going on? Andy Challenger, a vice president at Challenger, Gray & Christmas, says one big reason for the turnover remains a classic one: Aging leaders retiring and handing the reins to a younger successor. That trend may be increasing with an economic slowdown looming. Two thirds of corporate CFOs are predicting a recession within the next year, a Duke University survey found.

“It’s surprising to see so many changes right when a lot of stocks are about as high as they’ve ever been,” Challenger says. “Longer-tenured CEOs are stepping down when the company is in a pretty darn good position. With a lot of tensions on the horizon, some CEOs are finding now is the time to put their succession plans into action.”

Other reasons include pressure from activist investors (eBay, Samsung), health issues (HP, GoDaddy), turbulence during turnarounds (E*Trade, Norwegian Air). And increasingly, scandals and CEO misconduct are forcing boards to oust top managers in response to negative press and shareholder impatience.

“Corporate boards are beginning to recognize that bad behavior is not free. In fact, it can come at a very high cost, particularly when it emanates from the C-Suite,” says John Paul Rollert, a professor at the University of Chicago’s Booth School of Business. “If you are going to pay someone millions of dollars to lead a company, it doesn’t seem unreasonable to expect that person to actually be a leader.”

All these factors, along with accelerating product and innovation cycles, are shortening CEO tenures. In 2000, a CEO could expect to remain in office for at least eight years, but that average tenure has fallen to five years in the past decade, a recent report from PricewaterhouseCoopers said.

One silver lining is that the higher turnover may be opening up more opportunities for women executives to be named CEOs. Among CEO successors so far in 2019, 22% have women. And while Challenger calls that ratio “shocking small,” it’s up from 12% in 2010.

If the high CEO churn continues, there’s reason to expect that figure to rise further.

“Given the fact that women increasingly make up nearly 50% of the attendees at top MBA Programs, we can expect more women in the future to join the CEO ranks,” Rollert says. “It’s not the nature of culture to change overnight, but all signs suggest that women will increasingly be looked to for corporate leadership and will, in turn, pull other young women up into their ranks.”

More must-read stories from Fortune:

—WeWork IPO filing withdrawn as roadshow leads to a dead end
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—Charles Schwab on the lessons he’s learned over a lifetime of investing
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—“Performance chasing”—and why it can be perilous for your portfolio

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