When Murdoch steps down, Buffett to increase lead on this list

Rupert Murdoch
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With word that Rupert Murdoch is preparing to step down as CEO of 21st Century Fox, Warren Buffett would far and away increase his lead as the oldest CEO in the S&P 500.

Read More Murdoch preparing to step down as CEO

Murdoch, 84, is one of only two S&P 500 CEOs over age 81.

Read More Who is the oldest CEO in the S&P 500?

Berkshire Hathaway's Buffett is also 84, born a few months before Murdoch. Next oldest is Robert Wilmers of M&T Bank. Wilmers, who was listed as 80 in a March filing, had been CEO many years ago, retired and then came back to run it again.

So Buffett's lead gaps out from a few months to several years. No other CEOs are over 80, according to data from S&P Capital IQ.

The average age is in the mid-50s in every sector. Only one CEO, Facebook's Mark Zuckerberg, is under 40, at a youthful 31. Here are the average ranges, by sector, of CEO age in the S&P 500.

That raises the question—how long until Buffett himself moves on. After Buffett and Wilmers, only seven CEOs are in their 70s, topped by L Brands head Leslie Wexner, 77. Others include Ralph Lauren (75), Steve Wynn (75), Vornado's Steven Roth (born 1941), and Fred Smith of FedEx (70). If it weren't for Wilmers breaking his retirement and coming back, Buffett would have been seven years older than the next CEO on the list.