This is not to imply that the CEOs' industry experience is confined to their current role. In order to be as accurate with data compilation as possible, our research counted only the most recent CEO appointment at the current company as the start date, excluding prior leadership experience heading multinational subsidiaries, groups, divisions, or as the CEOs for competitors.

Something to consider are the basic differences between regions, countries, and industries. An example are the cultural norms about when someone can become a CEO, according to Timothy Quigley, a professor of strategic management at the University of Georgia. “In the U.S., it was once the norm that you had to be mid- to late-50s before coming CEO,” he says. Yet today the norm has shifted—becoming a CEO in one's late 30s or early 40s is possible.

Marissa Mayer was 37 when she became Yahoo! Inc.'s CEO, a position she held for just shy of five years, and Mark Zuckerburg was all but 28 when he took Facebook Inc public. Globally, half of the world's CEOs are in the 50-59 age group.

“Similarly, it used to be that lots of companies had mandatory retirement ages,” Quigley says. Merck & Co. recently rolled back a policy calling for its CEO to retire at the age of 65, allowing the drugmaker's current boss, Ken Frazier, to remain at the helm for longer.

In places where mandatory retirement and tougher promotional hierarchy squeeze both ends of the career spectrum—such as the Japanese market—as assessed by the Nikkei index members, it is probably no wonder that the average leader is 62.9 years old, one of the oldest, while having served as a CEO for only an average 4.4 years.

Some of the longest-serving CEOs for major equity index member companies may not represent their industry as a whole. Warren Buffett, one of the oldest CEOs at age 88, has been leading Berkshire Hathaway Inc, an SPX member, for 48.7 years. Rahul Bajaj, of Bajaj Auto Ltd, a maker of motorized scooters and one of the 31 current members of India's Sensex index, has been in the lead position for 50.8 years. Bernard Arnault, France's richest man, has been at the helm of luxury goods maker LVMH Moet Hennessy for nearly 30 years.

In this fast-paced world dominated by career mobility and misaligned incentives, “companies are dealing with uncertainty in the markets, disruptions in technology, or fallout from impending tariffs. Regardless of the reason, boards need strong talent with specific skill-sets,” said Andrew Challenger, vice president of Challenger, Gray & Christmas, Inc., a global outplacement consultancy.

Should something like the 2008 crisis happen again, even on a regional level, experience matters. Quigley agrees, “I think there's an argument to be made for keeping the steady hand at the helm in rough seas.”

Needless to say, Warren Buffetts are a rarity.

From: Bloomberg

Copyright 2018 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.