By Anupreeta Das 

Berkshire Hathaway Inc. Vice Chairman Charlie Munger dropped the biggest hint yet that the conglomerate's future chief executive could either be Ajit Jain, the head of its reinsurance business, or Greg Abel, who runs its energy business.

In a letter to shareholders sharing his thoughts about the past and future of Berkshire Hathaway, Mr. Munger said that Berkshire would remain a "better-than-normal" company with its current structure even if chairman and CEO Warren Buffett left the company tomorrow, his successors were persons of only moderate ability and Berkshire never bought another large business again.

"But, under this Buffett-soon-leaves assumption, his successors would not be "'of only moderate ability.'" For instance, Ajit Jain and Greg Abel are proven performers who would probably be under-described as "world-class," Mr. Munger wrote. He added that in some ways, "each is a better business executive than Buffett."

Mr. Munger also said that neither of the two executives is likely to leave Berkshire Hathaway or want to change the company's structure in a big way.

Mr. Munger appeared to be making a hypothetical case in naming the two men. But analysts and Berkshire shareholders have long speculated that Mr. Jain, 63, is the most likely candidate to succeed Mr. Buffett as CEO. Mr. Abel, who is about a decade younger, has been another name on investors' shortlists.

Both are longtime Berkshire executives. The India-born Mr. Jain is credited with building Berkshire's massive reinsurance business from scratch. Mr. Abel, meanwhile, joined Berkshire through its 2000 purchase of a utility company, and has built it into a large energy provider supplying 11 million customers globally.

For his part, Mr. Buffett said his successor would have to be a "rational, calm and decisive individual" with the ability to allocate capital and "fight off the ABCs of business decay, which are arrogance, bureaucracy and complacency."

In the section of his letter addressing the future of Berkshire, Mr. Buffett did not list any candidates by name. However, he said the board and he believe Berkshire has the "right person to succeed me as CEO... In certain important respects, this person will do a better job than I am doing."

Berkshire released the letter from its chairman Saturday morning along with its fourth-quarter and annual earnings report. Since 2015 marks the 50th year of Berkshire under the control of Mr. Buffett and his right-hand man Mr. Munger, the duo each wrote sections reviewing Berkshire over the past five decades and laying out their vision for the future.

Write to Anupreeta Das at anupreeta.das@wsj.com

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