The Similarities of—and Differences Between—the Top 20 and Bottom 20 Fortune 500 CEOs

There are some interesting similarities—and differences—between the career paths of CEOs of the top 20 firms on the Fortune 500 list, and those who head Nos. 481 through 500.

First, the average length of tenure at the top 20 companies was almost twice as much as their colleagues at the bottom of the list—27.2 years on average, versus 14.25. Some of the top 20 with the longest stay at their current firms included Berkshire Hathaway’s Warren E. Buffett, with 46 years; ExxonMobile’s Rex W. Tillerson, 41; Walgreens Boots Alliance’s Stefano Pessina, 39; Kroger’s W. Rodney McMullen, 38; General Motors’ Mary T. Barra, 36; Chevron’s John S. Watson, 36; AT&T’s Randall L. Stephenson, 34; General Electric’s Jeffrey R. Immelt, 34; and Costco’s W. Craig Jelinek, 32.

Still, there were some CEOs listed at the bottom who have had tenures just as long at their current companies, including Telephone & Data Systems’ LeRoy T. Carlson Jr., 42; Rockwell Collins’ Robert K. Ortberg, 29; First American Financial’s Dennis J. Gilmore, 25, NVR’s Paul C. Saville, 23; and Airgas’ Michael L. Molinini, 19.

On both sides, CEOs’ breath of experience was extensive—either at their current company, or at a number of companies throughout their career. For long-timers at their current company, No. 1 Walmart’s C. Douglas McMillon is particularly noteworthy: In 1984, he started out as an hourly summer associate in a Walmart distribution center while still in high school. In 1990, while pursuing his MBA, he rejoined the company as an assistant manager in a Tulsa, Okla., Walmart store before moving to merchandising as a buyer trainee. He went on to serve in senior leadership roles in all of Walmart’s business segments.

Another similarity between all of the CEOs—a majority got an MBA, though their undergraduate degrees were pretty varied, and many were not business-related. Some studied in the disciplines needed for core operations of the company, such as CVS’ Larry J. Merlo, who embarked on his career in the pharmacy industry after graduating from the University of Pittsburgh School of Pharmacy.

Then there are some whose degrees are completely unrelated to their chosen professions, such as Walgreens Boots Alliance’s Pessina, who graduated from the Polytechnic University of Milan with a degree in nuclear engineering. In 1977 he took over his family’s business—a pharmaceutical wholesaler in Naples, before turning it into Alliance Santé, a Franco-Italian pharmaceutical wholesale group.

2015 revenues for the top 20 on the list ranged between $103 billion and $482 billion, while last year’s revenues for the bottom 20 ranged between $5.13 million and $5.31 million.

Public companies actually make up a very small part of the company universe. There are actually many more privately held companies (200,000+ for privately held vs. 2,000+ for public companies). Among privately held companies, total executive compensation varies by type of job type, ownership, geography, industry and more. To find out more about the difference in compensation in private companies, click here.